2546 lines
134 KiB
ReStructuredText
2546 lines
134 KiB
ReStructuredText
================
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Event Histograms
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================
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Documentation written by Tom Zanussi
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1. Introduction
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===============
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Histogram triggers are special event triggers that can be used to
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aggregate trace event data into histograms. For information on
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trace events and event triggers, see Documentation/trace/events.rst.
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2. Histogram Trigger Command
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============================
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A histogram trigger command is an event trigger command that
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aggregates event hits into a hash table keyed on one or more trace
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event format fields (or stacktrace) and a set of running totals
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derived from one or more trace event format fields and/or event
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counts (hitcount).
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The format of a hist trigger is as follows::
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hist:keys=<field1[,field2,...]>[:values=<field1[,field2,...]>]
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[:sort=<field1[,field2,...]>][:size=#entries][:pause][:continue]
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[:clear][:name=histname1] [if <filter>]
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When a matching event is hit, an entry is added to a hash table
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using the key(s) and value(s) named. Keys and values correspond to
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fields in the event's format description. Values must correspond to
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numeric fields - on an event hit, the value(s) will be added to a
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sum kept for that field. The special string 'hitcount' can be used
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in place of an explicit value field - this is simply a count of
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event hits. If 'values' isn't specified, an implicit 'hitcount'
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value will be automatically created and used as the only value.
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Keys can be any field, or the special string 'stacktrace', which
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will use the event's kernel stacktrace as the key. The keywords
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'keys' or 'key' can be used to specify keys, and the keywords
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'values', 'vals', or 'val' can be used to specify values. Compound
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keys consisting of up to two fields can be specified by the 'keys'
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keyword. Hashing a compound key produces a unique entry in the
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table for each unique combination of component keys, and can be
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useful for providing more fine-grained summaries of event data.
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Additionally, sort keys consisting of up to two fields can be
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specified by the 'sort' keyword. If more than one field is
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specified, the result will be a 'sort within a sort': the first key
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is taken to be the primary sort key and the second the secondary
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key. If a hist trigger is given a name using the 'name' parameter,
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its histogram data will be shared with other triggers of the same
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name, and trigger hits will update this common data. Only triggers
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with 'compatible' fields can be combined in this way; triggers are
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'compatible' if the fields named in the trigger share the same
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number and type of fields and those fields also have the same names.
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Note that any two events always share the compatible 'hitcount' and
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'stacktrace' fields and can therefore be combined using those
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fields, however pointless that may be.
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'hist' triggers add a 'hist' file to each event's subdirectory.
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Reading the 'hist' file for the event will dump the hash table in
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its entirety to stdout. If there are multiple hist triggers
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attached to an event, there will be a table for each trigger in the
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output. The table displayed for a named trigger will be the same as
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any other instance having the same name. Each printed hash table
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entry is a simple list of the keys and values comprising the entry;
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keys are printed first and are delineated by curly braces, and are
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followed by the set of value fields for the entry. By default,
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numeric fields are displayed as base-10 integers. This can be
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modified by appending any of the following modifiers to the field
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name:
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=========== ==========================================
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.hex display a number as a hex value
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.sym display an address as a symbol
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.sym-offset display an address as a symbol and offset
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.syscall display a syscall id as a system call name
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.execname display a common_pid as a program name
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.log2 display log2 value rather than raw number
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.usecs display a common_timestamp in microseconds
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=========== ==========================================
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Note that in general the semantics of a given field aren't
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interpreted when applying a modifier to it, but there are some
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restrictions to be aware of in this regard:
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- only the 'hex' modifier can be used for values (because values
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are essentially sums, and the other modifiers don't make sense
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in that context).
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- the 'execname' modifier can only be used on a 'common_pid'. The
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reason for this is that the execname is simply the 'comm' value
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saved for the 'current' process when an event was triggered,
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which is the same as the common_pid value saved by the event
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tracing code. Trying to apply that comm value to other pid
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values wouldn't be correct, and typically events that care save
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pid-specific comm fields in the event itself.
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A typical usage scenario would be the following to enable a hist
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trigger, read its current contents, and then turn it off::
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# echo 'hist:keys=skbaddr.hex:vals=len' > \
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/sys/kernel/debug/tracing/events/net/netif_rx/trigger
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# cat /sys/kernel/debug/tracing/events/net/netif_rx/hist
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# echo '!hist:keys=skbaddr.hex:vals=len' > \
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/sys/kernel/debug/tracing/events/net/netif_rx/trigger
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The trigger file itself can be read to show the details of the
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currently attached hist trigger. This information is also displayed
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at the top of the 'hist' file when read.
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By default, the size of the hash table is 2048 entries. The 'size'
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parameter can be used to specify more or fewer than that. The units
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are in terms of hashtable entries - if a run uses more entries than
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specified, the results will show the number of 'drops', the number
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of hits that were ignored. The size should be a power of 2 between
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128 and 131072 (any non- power-of-2 number specified will be rounded
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up).
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The 'sort' parameter can be used to specify a value field to sort
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on. The default if unspecified is 'hitcount' and the default sort
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order is 'ascending'. To sort in the opposite direction, append
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.descending' to the sort key.
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The 'pause' parameter can be used to pause an existing hist trigger
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or to start a hist trigger but not log any events until told to do
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so. 'continue' or 'cont' can be used to start or restart a paused
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hist trigger.
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The 'clear' parameter will clear the contents of a running hist
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trigger and leave its current paused/active state.
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Note that the 'pause', 'cont', and 'clear' parameters should be
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applied using 'append' shell operator ('>>') if applied to an
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existing trigger, rather than via the '>' operator, which will cause
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the trigger to be removed through truncation.
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- enable_hist/disable_hist
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The enable_hist and disable_hist triggers can be used to have one
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event conditionally start and stop another event's already-attached
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hist trigger. Any number of enable_hist and disable_hist triggers
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can be attached to a given event, allowing that event to kick off
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and stop aggregations on a host of other events.
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The format is very similar to the enable/disable_event triggers::
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enable_hist:<system>:<event>[:count]
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disable_hist:<system>:<event>[:count]
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Instead of enabling or disabling the tracing of the target event
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into the trace buffer as the enable/disable_event triggers do, the
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enable/disable_hist triggers enable or disable the aggregation of
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the target event into a hash table.
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A typical usage scenario for the enable_hist/disable_hist triggers
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would be to first set up a paused hist trigger on some event,
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followed by an enable_hist/disable_hist pair that turns the hist
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aggregation on and off when conditions of interest are hit::
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# echo 'hist:keys=skbaddr.hex:vals=len:pause' > \
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/sys/kernel/debug/tracing/events/net/netif_receive_skb/trigger
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# echo 'enable_hist:net:netif_receive_skb if filename==/usr/bin/wget' > \
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/sys/kernel/debug/tracing/events/sched/sched_process_exec/trigger
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# echo 'disable_hist:net:netif_receive_skb if comm==wget' > \
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/sys/kernel/debug/tracing/events/sched/sched_process_exit/trigger
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The above sets up an initially paused hist trigger which is unpaused
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and starts aggregating events when a given program is executed, and
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which stops aggregating when the process exits and the hist trigger
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is paused again.
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The examples below provide a more concrete illustration of the
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concepts and typical usage patterns discussed above.
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'special' event fields
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------------------------
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There are a number of 'special event fields' available for use as
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keys or values in a hist trigger. These look like and behave as if
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they were actual event fields, but aren't really part of the event's
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field definition or format file. They are however available for any
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event, and can be used anywhere an actual event field could be.
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They are:
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====================== ==== =======================================
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common_timestamp u64 timestamp (from ring buffer) associated
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with the event, in nanoseconds. May be
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modified by .usecs to have timestamps
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interpreted as microseconds.
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cpu int the cpu on which the event occurred.
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====================== ==== =======================================
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Extended error information
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--------------------------
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For some error conditions encountered when invoking a hist trigger
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command, extended error information is available via the
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corresponding event's 'hist' file. Reading the hist file after an
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error will display more detailed information about what went wrong,
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if information is available. This extended error information will
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be available until the next hist trigger command for that event.
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If available for a given error condition, the extended error
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information and usage takes the following form::
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# echo xxx > /sys/kernel/debug/tracing/events/sched/sched_wakeup/trigger
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echo: write error: Invalid argument
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# cat /sys/kernel/debug/tracing/events/sched/sched_wakeup/hist
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ERROR: Couldn't yyy: zzz
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Last command: xxx
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6.2 'hist' trigger examples
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---------------------------
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The first set of examples creates aggregations using the kmalloc
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event. The fields that can be used for the hist trigger are listed
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in the kmalloc event's format file::
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# cat /sys/kernel/debug/tracing/events/kmem/kmalloc/format
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name: kmalloc
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ID: 374
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format:
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field:unsigned short common_type; offset:0; size:2; signed:0;
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field:unsigned char common_flags; offset:2; size:1; signed:0;
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field:unsigned char common_preempt_count; offset:3; size:1; signed:0;
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field:int common_pid; offset:4; size:4; signed:1;
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field:unsigned long call_site; offset:8; size:8; signed:0;
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field:const void * ptr; offset:16; size:8; signed:0;
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field:size_t bytes_req; offset:24; size:8; signed:0;
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field:size_t bytes_alloc; offset:32; size:8; signed:0;
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field:gfp_t gfp_flags; offset:40; size:4; signed:0;
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We'll start by creating a hist trigger that generates a simple table
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that lists the total number of bytes requested for each function in
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the kernel that made one or more calls to kmalloc::
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# echo 'hist:key=call_site:val=bytes_req' > \
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/sys/kernel/debug/tracing/events/kmem/kmalloc/trigger
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This tells the tracing system to create a 'hist' trigger using the
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call_site field of the kmalloc event as the key for the table, which
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just means that each unique call_site address will have an entry
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created for it in the table. The 'val=bytes_req' parameter tells
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the hist trigger that for each unique entry (call_site) in the
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table, it should keep a running total of the number of bytes
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requested by that call_site.
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We'll let it run for awhile and then dump the contents of the 'hist'
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file in the kmalloc event's subdirectory (for readability, a number
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of entries have been omitted)::
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# cat /sys/kernel/debug/tracing/events/kmem/kmalloc/hist
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# trigger info: hist:keys=call_site:vals=bytes_req:sort=hitcount:size=2048 [active]
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{ call_site: 18446744072106379007 } hitcount: 1 bytes_req: 176
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{ call_site: 18446744071579557049 } hitcount: 1 bytes_req: 1024
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{ call_site: 18446744071580608289 } hitcount: 1 bytes_req: 16384
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{ call_site: 18446744071581827654 } hitcount: 1 bytes_req: 24
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{ call_site: 18446744071580700980 } hitcount: 1 bytes_req: 8
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{ call_site: 18446744071579359876 } hitcount: 1 bytes_req: 152
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{ call_site: 18446744071580795365 } hitcount: 3 bytes_req: 144
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{ call_site: 18446744071581303129 } hitcount: 3 bytes_req: 144
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{ call_site: 18446744071580713234 } hitcount: 4 bytes_req: 2560
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{ call_site: 18446744071580933750 } hitcount: 4 bytes_req: 736
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.
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.
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.
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{ call_site: 18446744072106047046 } hitcount: 69 bytes_req: 5576
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{ call_site: 18446744071582116407 } hitcount: 73 bytes_req: 2336
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{ call_site: 18446744072106054684 } hitcount: 136 bytes_req: 140504
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{ call_site: 18446744072106224230 } hitcount: 136 bytes_req: 19584
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{ call_site: 18446744072106078074 } hitcount: 153 bytes_req: 2448
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{ call_site: 18446744072106062406 } hitcount: 153 bytes_req: 36720
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{ call_site: 18446744071582507929 } hitcount: 153 bytes_req: 37088
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{ call_site: 18446744072102520590 } hitcount: 273 bytes_req: 10920
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{ call_site: 18446744071582143559 } hitcount: 358 bytes_req: 716
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{ call_site: 18446744072106465852 } hitcount: 417 bytes_req: 56712
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{ call_site: 18446744072102523378 } hitcount: 485 bytes_req: 27160
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{ call_site: 18446744072099568646 } hitcount: 1676 bytes_req: 33520
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Totals:
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Hits: 4610
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Entries: 45
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Dropped: 0
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The output displays a line for each entry, beginning with the key
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specified in the trigger, followed by the value(s) also specified in
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the trigger. At the beginning of the output is a line that displays
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the trigger info, which can also be displayed by reading the
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'trigger' file::
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# cat /sys/kernel/debug/tracing/events/kmem/kmalloc/trigger
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hist:keys=call_site:vals=bytes_req:sort=hitcount:size=2048 [active]
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At the end of the output are a few lines that display the overall
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totals for the run. The 'Hits' field shows the total number of
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times the event trigger was hit, the 'Entries' field shows the total
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number of used entries in the hash table, and the 'Dropped' field
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shows the number of hits that were dropped because the number of
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used entries for the run exceeded the maximum number of entries
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allowed for the table (normally 0, but if not a hint that you may
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want to increase the size of the table using the 'size' parameter).
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Notice in the above output that there's an extra field, 'hitcount',
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which wasn't specified in the trigger. Also notice that in the
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trigger info output, there's a parameter, 'sort=hitcount', which
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wasn't specified in the trigger either. The reason for that is that
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every trigger implicitly keeps a count of the total number of hits
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attributed to a given entry, called the 'hitcount'. That hitcount
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information is explicitly displayed in the output, and in the
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absence of a user-specified sort parameter, is used as the default
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sort field.
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The value 'hitcount' can be used in place of an explicit value in
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the 'values' parameter if you don't really need to have any
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particular field summed and are mainly interested in hit
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frequencies.
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To turn the hist trigger off, simply call up the trigger in the
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command history and re-execute it with a '!' prepended::
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# echo '!hist:key=call_site:val=bytes_req' > \
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/sys/kernel/debug/tracing/events/kmem/kmalloc/trigger
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Finally, notice that the call_site as displayed in the output above
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isn't really very useful. It's an address, but normally addresses
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are displayed in hex. To have a numeric field displayed as a hex
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value, simply append '.hex' to the field name in the trigger::
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# echo 'hist:key=call_site.hex:val=bytes_req' > \
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/sys/kernel/debug/tracing/events/kmem/kmalloc/trigger
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# cat /sys/kernel/debug/tracing/events/kmem/kmalloc/hist
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# trigger info: hist:keys=call_site.hex:vals=bytes_req:sort=hitcount:size=2048 [active]
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{ call_site: ffffffffa026b291 } hitcount: 1 bytes_req: 433
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{ call_site: ffffffffa07186ff } hitcount: 1 bytes_req: 176
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{ call_site: ffffffff811ae721 } hitcount: 1 bytes_req: 16384
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{ call_site: ffffffff811c5134 } hitcount: 1 bytes_req: 8
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{ call_site: ffffffffa04a9ebb } hitcount: 1 bytes_req: 511
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{ call_site: ffffffff8122e0a6 } hitcount: 1 bytes_req: 12
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{ call_site: ffffffff8107da84 } hitcount: 1 bytes_req: 152
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{ call_site: ffffffff812d8246 } hitcount: 1 bytes_req: 24
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{ call_site: ffffffff811dc1e5 } hitcount: 3 bytes_req: 144
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{ call_site: ffffffffa02515e8 } hitcount: 3 bytes_req: 648
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{ call_site: ffffffff81258159 } hitcount: 3 bytes_req: 144
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{ call_site: ffffffff811c80f4 } hitcount: 4 bytes_req: 544
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.
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.
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.
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{ call_site: ffffffffa06c7646 } hitcount: 106 bytes_req: 8024
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{ call_site: ffffffffa06cb246 } hitcount: 132 bytes_req: 31680
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{ call_site: ffffffffa06cef7a } hitcount: 132 bytes_req: 2112
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{ call_site: ffffffff8137e399 } hitcount: 132 bytes_req: 23232
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{ call_site: ffffffffa06c941c } hitcount: 185 bytes_req: 171360
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{ call_site: ffffffffa06f2a66 } hitcount: 185 bytes_req: 26640
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{ call_site: ffffffffa036a70e } hitcount: 265 bytes_req: 10600
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{ call_site: ffffffff81325447 } hitcount: 292 bytes_req: 584
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{ call_site: ffffffffa072da3c } hitcount: 446 bytes_req: 60656
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{ call_site: ffffffffa036b1f2 } hitcount: 526 bytes_req: 29456
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{ call_site: ffffffffa0099c06 } hitcount: 1780 bytes_req: 35600
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Totals:
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Hits: 4775
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Entries: 46
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Dropped: 0
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Even that's only marginally more useful - while hex values do look
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more like addresses, what users are typically more interested in
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when looking at text addresses are the corresponding symbols
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instead. To have an address displayed as symbolic value instead,
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simply append '.sym' or '.sym-offset' to the field name in the
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trigger::
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# echo 'hist:key=call_site.sym:val=bytes_req' > \
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/sys/kernel/debug/tracing/events/kmem/kmalloc/trigger
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# cat /sys/kernel/debug/tracing/events/kmem/kmalloc/hist
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# trigger info: hist:keys=call_site.sym:vals=bytes_req:sort=hitcount:size=2048 [active]
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{ call_site: [ffffffff810adcb9] syslog_print_all } hitcount: 1 bytes_req: 1024
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{ call_site: [ffffffff8154bc62] usb_control_msg } hitcount: 1 bytes_req: 8
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{ call_site: [ffffffffa00bf6fe] hidraw_send_report [hid] } hitcount: 1 bytes_req: 7
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{ call_site: [ffffffff8154acbe] usb_alloc_urb } hitcount: 1 bytes_req: 192
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{ call_site: [ffffffffa00bf1ca] hidraw_report_event [hid] } hitcount: 1 bytes_req: 7
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{ call_site: [ffffffff811e3a25] __seq_open_private } hitcount: 1 bytes_req: 40
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{ call_site: [ffffffff8109524a] alloc_fair_sched_group } hitcount: 2 bytes_req: 128
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{ call_site: [ffffffff811febd5] fsnotify_alloc_group } hitcount: 2 bytes_req: 528
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{ call_site: [ffffffff81440f58] __tty_buffer_request_room } hitcount: 2 bytes_req: 2624
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{ call_site: [ffffffff81200ba6] inotify_new_group } hitcount: 2 bytes_req: 96
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{ call_site: [ffffffffa05e19af] ieee80211_start_tx_ba_session [mac80211] } hitcount: 2 bytes_req: 464
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{ call_site: [ffffffff81672406] tcp_get_metrics } hitcount: 2 bytes_req: 304
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{ call_site: [ffffffff81097ec2] alloc_rt_sched_group } hitcount: 2 bytes_req: 128
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{ call_site: [ffffffff81089b05] sched_create_group } hitcount: 2 bytes_req: 1424
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.
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.
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.
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{ call_site: [ffffffffa04a580c] intel_crtc_page_flip [i915] } hitcount: 1185 bytes_req: 123240
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{ call_site: [ffffffffa0287592] drm_mode_page_flip_ioctl [drm] } hitcount: 1185 bytes_req: 104280
|
|
{ call_site: [ffffffffa04c4a3c] intel_plane_duplicate_state [i915] } hitcount: 1402 bytes_req: 190672
|
|
{ call_site: [ffffffff812891ca] ext4_find_extent } hitcount: 1518 bytes_req: 146208
|
|
{ call_site: [ffffffffa029070e] drm_vma_node_allow [drm] } hitcount: 1746 bytes_req: 69840
|
|
{ call_site: [ffffffffa045e7c4] i915_gem_do_execbuffer.isra.23 [i915] } hitcount: 2021 bytes_req: 792312
|
|
{ call_site: [ffffffffa02911f2] drm_modeset_lock_crtc [drm] } hitcount: 2592 bytes_req: 145152
|
|
{ call_site: [ffffffffa0489a66] intel_ring_begin [i915] } hitcount: 2629 bytes_req: 378576
|
|
{ call_site: [ffffffffa046041c] i915_gem_execbuffer2 [i915] } hitcount: 2629 bytes_req: 3783248
|
|
{ call_site: [ffffffff81325607] apparmor_file_alloc_security } hitcount: 5192 bytes_req: 10384
|
|
{ call_site: [ffffffffa00b7c06] hid_report_raw_event [hid] } hitcount: 5529 bytes_req: 110584
|
|
{ call_site: [ffffffff8131ebf7] aa_alloc_task_context } hitcount: 21943 bytes_req: 702176
|
|
{ call_site: [ffffffff8125847d] ext4_htree_store_dirent } hitcount: 55759 bytes_req: 5074265
|
|
|
|
Totals:
|
|
Hits: 109928
|
|
Entries: 71
|
|
Dropped: 0
|
|
|
|
Because the default sort key above is 'hitcount', the above shows a
|
|
the list of call_sites by increasing hitcount, so that at the bottom
|
|
we see the functions that made the most kmalloc calls during the
|
|
run. If instead we we wanted to see the top kmalloc callers in
|
|
terms of the number of bytes requested rather than the number of
|
|
calls, and we wanted the top caller to appear at the top, we can use
|
|
the 'sort' parameter, along with the 'descending' modifier::
|
|
|
|
# echo 'hist:key=call_site.sym:val=bytes_req:sort=bytes_req.descending' > \
|
|
/sys/kernel/debug/tracing/events/kmem/kmalloc/trigger
|
|
|
|
# cat /sys/kernel/debug/tracing/events/kmem/kmalloc/hist
|
|
# trigger info: hist:keys=call_site.sym:vals=bytes_req:sort=bytes_req.descending:size=2048 [active]
|
|
|
|
{ call_site: [ffffffffa046041c] i915_gem_execbuffer2 [i915] } hitcount: 2186 bytes_req: 3397464
|
|
{ call_site: [ffffffffa045e7c4] i915_gem_do_execbuffer.isra.23 [i915] } hitcount: 1790 bytes_req: 712176
|
|
{ call_site: [ffffffff8125847d] ext4_htree_store_dirent } hitcount: 8132 bytes_req: 513135
|
|
{ call_site: [ffffffff811e2a1b] seq_buf_alloc } hitcount: 106 bytes_req: 440128
|
|
{ call_site: [ffffffffa0489a66] intel_ring_begin [i915] } hitcount: 2186 bytes_req: 314784
|
|
{ call_site: [ffffffff812891ca] ext4_find_extent } hitcount: 2174 bytes_req: 208992
|
|
{ call_site: [ffffffff811ae8e1] __kmalloc } hitcount: 8 bytes_req: 131072
|
|
{ call_site: [ffffffffa04c4a3c] intel_plane_duplicate_state [i915] } hitcount: 859 bytes_req: 116824
|
|
{ call_site: [ffffffffa02911f2] drm_modeset_lock_crtc [drm] } hitcount: 1834 bytes_req: 102704
|
|
{ call_site: [ffffffffa04a580c] intel_crtc_page_flip [i915] } hitcount: 972 bytes_req: 101088
|
|
{ call_site: [ffffffffa0287592] drm_mode_page_flip_ioctl [drm] } hitcount: 972 bytes_req: 85536
|
|
{ call_site: [ffffffffa00b7c06] hid_report_raw_event [hid] } hitcount: 3333 bytes_req: 66664
|
|
{ call_site: [ffffffff8137e559] sg_kmalloc } hitcount: 209 bytes_req: 61632
|
|
.
|
|
.
|
|
.
|
|
{ call_site: [ffffffff81095225] alloc_fair_sched_group } hitcount: 2 bytes_req: 128
|
|
{ call_site: [ffffffff81097ec2] alloc_rt_sched_group } hitcount: 2 bytes_req: 128
|
|
{ call_site: [ffffffff812d8406] copy_semundo } hitcount: 2 bytes_req: 48
|
|
{ call_site: [ffffffff81200ba6] inotify_new_group } hitcount: 1 bytes_req: 48
|
|
{ call_site: [ffffffffa027121a] drm_getmagic [drm] } hitcount: 1 bytes_req: 48
|
|
{ call_site: [ffffffff811e3a25] __seq_open_private } hitcount: 1 bytes_req: 40
|
|
{ call_site: [ffffffff811c52f4] bprm_change_interp } hitcount: 2 bytes_req: 16
|
|
{ call_site: [ffffffff8154bc62] usb_control_msg } hitcount: 1 bytes_req: 8
|
|
{ call_site: [ffffffffa00bf1ca] hidraw_report_event [hid] } hitcount: 1 bytes_req: 7
|
|
{ call_site: [ffffffffa00bf6fe] hidraw_send_report [hid] } hitcount: 1 bytes_req: 7
|
|
|
|
Totals:
|
|
Hits: 32133
|
|
Entries: 81
|
|
Dropped: 0
|
|
|
|
To display the offset and size information in addition to the symbol
|
|
name, just use 'sym-offset' instead::
|
|
|
|
# echo 'hist:key=call_site.sym-offset:val=bytes_req:sort=bytes_req.descending' > \
|
|
/sys/kernel/debug/tracing/events/kmem/kmalloc/trigger
|
|
|
|
# cat /sys/kernel/debug/tracing/events/kmem/kmalloc/hist
|
|
# trigger info: hist:keys=call_site.sym-offset:vals=bytes_req:sort=bytes_req.descending:size=2048 [active]
|
|
|
|
{ call_site: [ffffffffa046041c] i915_gem_execbuffer2+0x6c/0x2c0 [i915] } hitcount: 4569 bytes_req: 3163720
|
|
{ call_site: [ffffffffa0489a66] intel_ring_begin+0xc6/0x1f0 [i915] } hitcount: 4569 bytes_req: 657936
|
|
{ call_site: [ffffffffa045e7c4] i915_gem_do_execbuffer.isra.23+0x694/0x1020 [i915] } hitcount: 1519 bytes_req: 472936
|
|
{ call_site: [ffffffffa045e646] i915_gem_do_execbuffer.isra.23+0x516/0x1020 [i915] } hitcount: 3050 bytes_req: 211832
|
|
{ call_site: [ffffffff811e2a1b] seq_buf_alloc+0x1b/0x50 } hitcount: 34 bytes_req: 148384
|
|
{ call_site: [ffffffffa04a580c] intel_crtc_page_flip+0xbc/0x870 [i915] } hitcount: 1385 bytes_req: 144040
|
|
{ call_site: [ffffffff811ae8e1] __kmalloc+0x191/0x1b0 } hitcount: 8 bytes_req: 131072
|
|
{ call_site: [ffffffffa0287592] drm_mode_page_flip_ioctl+0x282/0x360 [drm] } hitcount: 1385 bytes_req: 121880
|
|
{ call_site: [ffffffffa02911f2] drm_modeset_lock_crtc+0x32/0x100 [drm] } hitcount: 1848 bytes_req: 103488
|
|
{ call_site: [ffffffffa04c4a3c] intel_plane_duplicate_state+0x2c/0xa0 [i915] } hitcount: 461 bytes_req: 62696
|
|
{ call_site: [ffffffffa029070e] drm_vma_node_allow+0x2e/0xd0 [drm] } hitcount: 1541 bytes_req: 61640
|
|
{ call_site: [ffffffff815f8d7b] sk_prot_alloc+0xcb/0x1b0 } hitcount: 57 bytes_req: 57456
|
|
.
|
|
.
|
|
.
|
|
{ call_site: [ffffffff8109524a] alloc_fair_sched_group+0x5a/0x1a0 } hitcount: 2 bytes_req: 128
|
|
{ call_site: [ffffffffa027b921] drm_vm_open_locked+0x31/0xa0 [drm] } hitcount: 3 bytes_req: 96
|
|
{ call_site: [ffffffff8122e266] proc_self_follow_link+0x76/0xb0 } hitcount: 8 bytes_req: 96
|
|
{ call_site: [ffffffff81213e80] load_elf_binary+0x240/0x1650 } hitcount: 3 bytes_req: 84
|
|
{ call_site: [ffffffff8154bc62] usb_control_msg+0x42/0x110 } hitcount: 1 bytes_req: 8
|
|
{ call_site: [ffffffffa00bf6fe] hidraw_send_report+0x7e/0x1a0 [hid] } hitcount: 1 bytes_req: 7
|
|
{ call_site: [ffffffffa00bf1ca] hidraw_report_event+0x8a/0x120 [hid] } hitcount: 1 bytes_req: 7
|
|
|
|
Totals:
|
|
Hits: 26098
|
|
Entries: 64
|
|
Dropped: 0
|
|
|
|
We can also add multiple fields to the 'values' parameter. For
|
|
example, we might want to see the total number of bytes allocated
|
|
alongside bytes requested, and display the result sorted by bytes
|
|
allocated in a descending order::
|
|
|
|
# echo 'hist:keys=call_site.sym:values=bytes_req,bytes_alloc:sort=bytes_alloc.descending' > \
|
|
/sys/kernel/debug/tracing/events/kmem/kmalloc/trigger
|
|
|
|
# cat /sys/kernel/debug/tracing/events/kmem/kmalloc/hist
|
|
# trigger info: hist:keys=call_site.sym:vals=bytes_req,bytes_alloc:sort=bytes_alloc.descending:size=2048 [active]
|
|
|
|
{ call_site: [ffffffffa046041c] i915_gem_execbuffer2 [i915] } hitcount: 7403 bytes_req: 4084360 bytes_alloc: 5958016
|
|
{ call_site: [ffffffff811e2a1b] seq_buf_alloc } hitcount: 541 bytes_req: 2213968 bytes_alloc: 2228224
|
|
{ call_site: [ffffffffa0489a66] intel_ring_begin [i915] } hitcount: 7404 bytes_req: 1066176 bytes_alloc: 1421568
|
|
{ call_site: [ffffffffa045e7c4] i915_gem_do_execbuffer.isra.23 [i915] } hitcount: 1565 bytes_req: 557368 bytes_alloc: 1037760
|
|
{ call_site: [ffffffff8125847d] ext4_htree_store_dirent } hitcount: 9557 bytes_req: 595778 bytes_alloc: 695744
|
|
{ call_site: [ffffffffa045e646] i915_gem_do_execbuffer.isra.23 [i915] } hitcount: 5839 bytes_req: 430680 bytes_alloc: 470400
|
|
{ call_site: [ffffffffa04c4a3c] intel_plane_duplicate_state [i915] } hitcount: 2388 bytes_req: 324768 bytes_alloc: 458496
|
|
{ call_site: [ffffffffa02911f2] drm_modeset_lock_crtc [drm] } hitcount: 3911 bytes_req: 219016 bytes_alloc: 250304
|
|
{ call_site: [ffffffff815f8d7b] sk_prot_alloc } hitcount: 235 bytes_req: 236880 bytes_alloc: 240640
|
|
{ call_site: [ffffffff8137e559] sg_kmalloc } hitcount: 557 bytes_req: 169024 bytes_alloc: 221760
|
|
{ call_site: [ffffffffa00b7c06] hid_report_raw_event [hid] } hitcount: 9378 bytes_req: 187548 bytes_alloc: 206312
|
|
{ call_site: [ffffffffa04a580c] intel_crtc_page_flip [i915] } hitcount: 1519 bytes_req: 157976 bytes_alloc: 194432
|
|
.
|
|
.
|
|
.
|
|
{ call_site: [ffffffff8109bd3b] sched_autogroup_create_attach } hitcount: 2 bytes_req: 144 bytes_alloc: 192
|
|
{ call_site: [ffffffff81097ee8] alloc_rt_sched_group } hitcount: 2 bytes_req: 128 bytes_alloc: 128
|
|
{ call_site: [ffffffff8109524a] alloc_fair_sched_group } hitcount: 2 bytes_req: 128 bytes_alloc: 128
|
|
{ call_site: [ffffffff81095225] alloc_fair_sched_group } hitcount: 2 bytes_req: 128 bytes_alloc: 128
|
|
{ call_site: [ffffffff81097ec2] alloc_rt_sched_group } hitcount: 2 bytes_req: 128 bytes_alloc: 128
|
|
{ call_site: [ffffffff81213e80] load_elf_binary } hitcount: 3 bytes_req: 84 bytes_alloc: 96
|
|
{ call_site: [ffffffff81079a2e] kthread_create_on_node } hitcount: 1 bytes_req: 56 bytes_alloc: 64
|
|
{ call_site: [ffffffffa00bf6fe] hidraw_send_report [hid] } hitcount: 1 bytes_req: 7 bytes_alloc: 8
|
|
{ call_site: [ffffffff8154bc62] usb_control_msg } hitcount: 1 bytes_req: 8 bytes_alloc: 8
|
|
{ call_site: [ffffffffa00bf1ca] hidraw_report_event [hid] } hitcount: 1 bytes_req: 7 bytes_alloc: 8
|
|
|
|
Totals:
|
|
Hits: 66598
|
|
Entries: 65
|
|
Dropped: 0
|
|
|
|
Finally, to finish off our kmalloc example, instead of simply having
|
|
the hist trigger display symbolic call_sites, we can have the hist
|
|
trigger additionally display the complete set of kernel stack traces
|
|
that led to each call_site. To do that, we simply use the special
|
|
value 'stacktrace' for the key parameter::
|
|
|
|
# echo 'hist:keys=stacktrace:values=bytes_req,bytes_alloc:sort=bytes_alloc' > \
|
|
/sys/kernel/debug/tracing/events/kmem/kmalloc/trigger
|
|
|
|
The above trigger will use the kernel stack trace in effect when an
|
|
event is triggered as the key for the hash table. This allows the
|
|
enumeration of every kernel callpath that led up to a particular
|
|
event, along with a running total of any of the event fields for
|
|
that event. Here we tally bytes requested and bytes allocated for
|
|
every callpath in the system that led up to a kmalloc (in this case
|
|
every callpath to a kmalloc for a kernel compile)::
|
|
|
|
# cat /sys/kernel/debug/tracing/events/kmem/kmalloc/hist
|
|
# trigger info: hist:keys=stacktrace:vals=bytes_req,bytes_alloc:sort=bytes_alloc:size=2048 [active]
|
|
|
|
{ stacktrace:
|
|
__kmalloc_track_caller+0x10b/0x1a0
|
|
kmemdup+0x20/0x50
|
|
hidraw_report_event+0x8a/0x120 [hid]
|
|
hid_report_raw_event+0x3ea/0x440 [hid]
|
|
hid_input_report+0x112/0x190 [hid]
|
|
hid_irq_in+0xc2/0x260 [usbhid]
|
|
__usb_hcd_giveback_urb+0x72/0x120
|
|
usb_giveback_urb_bh+0x9e/0xe0
|
|
tasklet_hi_action+0xf8/0x100
|
|
__do_softirq+0x114/0x2c0
|
|
irq_exit+0xa5/0xb0
|
|
do_IRQ+0x5a/0xf0
|
|
ret_from_intr+0x0/0x30
|
|
cpuidle_enter+0x17/0x20
|
|
cpu_startup_entry+0x315/0x3e0
|
|
rest_init+0x7c/0x80
|
|
} hitcount: 3 bytes_req: 21 bytes_alloc: 24
|
|
{ stacktrace:
|
|
__kmalloc_track_caller+0x10b/0x1a0
|
|
kmemdup+0x20/0x50
|
|
hidraw_report_event+0x8a/0x120 [hid]
|
|
hid_report_raw_event+0x3ea/0x440 [hid]
|
|
hid_input_report+0x112/0x190 [hid]
|
|
hid_irq_in+0xc2/0x260 [usbhid]
|
|
__usb_hcd_giveback_urb+0x72/0x120
|
|
usb_giveback_urb_bh+0x9e/0xe0
|
|
tasklet_hi_action+0xf8/0x100
|
|
__do_softirq+0x114/0x2c0
|
|
irq_exit+0xa5/0xb0
|
|
do_IRQ+0x5a/0xf0
|
|
ret_from_intr+0x0/0x30
|
|
} hitcount: 3 bytes_req: 21 bytes_alloc: 24
|
|
{ stacktrace:
|
|
kmem_cache_alloc_trace+0xeb/0x150
|
|
aa_alloc_task_context+0x27/0x40
|
|
apparmor_cred_prepare+0x1f/0x50
|
|
security_prepare_creds+0x16/0x20
|
|
prepare_creds+0xdf/0x1a0
|
|
SyS_capset+0xb5/0x200
|
|
system_call_fastpath+0x12/0x6a
|
|
} hitcount: 1 bytes_req: 32 bytes_alloc: 32
|
|
.
|
|
.
|
|
.
|
|
{ stacktrace:
|
|
__kmalloc+0x11b/0x1b0
|
|
i915_gem_execbuffer2+0x6c/0x2c0 [i915]
|
|
drm_ioctl+0x349/0x670 [drm]
|
|
do_vfs_ioctl+0x2f0/0x4f0
|
|
SyS_ioctl+0x81/0xa0
|
|
system_call_fastpath+0x12/0x6a
|
|
} hitcount: 17726 bytes_req: 13944120 bytes_alloc: 19593808
|
|
{ stacktrace:
|
|
__kmalloc+0x11b/0x1b0
|
|
load_elf_phdrs+0x76/0xa0
|
|
load_elf_binary+0x102/0x1650
|
|
search_binary_handler+0x97/0x1d0
|
|
do_execveat_common.isra.34+0x551/0x6e0
|
|
SyS_execve+0x3a/0x50
|
|
return_from_execve+0x0/0x23
|
|
} hitcount: 33348 bytes_req: 17152128 bytes_alloc: 20226048
|
|
{ stacktrace:
|
|
kmem_cache_alloc_trace+0xeb/0x150
|
|
apparmor_file_alloc_security+0x27/0x40
|
|
security_file_alloc+0x16/0x20
|
|
get_empty_filp+0x93/0x1c0
|
|
path_openat+0x31/0x5f0
|
|
do_filp_open+0x3a/0x90
|
|
do_sys_open+0x128/0x220
|
|
SyS_open+0x1e/0x20
|
|
system_call_fastpath+0x12/0x6a
|
|
} hitcount: 4766422 bytes_req: 9532844 bytes_alloc: 38131376
|
|
{ stacktrace:
|
|
__kmalloc+0x11b/0x1b0
|
|
seq_buf_alloc+0x1b/0x50
|
|
seq_read+0x2cc/0x370
|
|
proc_reg_read+0x3d/0x80
|
|
__vfs_read+0x28/0xe0
|
|
vfs_read+0x86/0x140
|
|
SyS_read+0x46/0xb0
|
|
system_call_fastpath+0x12/0x6a
|
|
} hitcount: 19133 bytes_req: 78368768 bytes_alloc: 78368768
|
|
|
|
Totals:
|
|
Hits: 6085872
|
|
Entries: 253
|
|
Dropped: 0
|
|
|
|
If you key a hist trigger on common_pid, in order for example to
|
|
gather and display sorted totals for each process, you can use the
|
|
special .execname modifier to display the executable names for the
|
|
processes in the table rather than raw pids. The example below
|
|
keeps a per-process sum of total bytes read::
|
|
|
|
# echo 'hist:key=common_pid.execname:val=count:sort=count.descending' > \
|
|
/sys/kernel/debug/tracing/events/syscalls/sys_enter_read/trigger
|
|
|
|
# cat /sys/kernel/debug/tracing/events/syscalls/sys_enter_read/hist
|
|
# trigger info: hist:keys=common_pid.execname:vals=count:sort=count.descending:size=2048 [active]
|
|
|
|
{ common_pid: gnome-terminal [ 3196] } hitcount: 280 count: 1093512
|
|
{ common_pid: Xorg [ 1309] } hitcount: 525 count: 256640
|
|
{ common_pid: compiz [ 2889] } hitcount: 59 count: 254400
|
|
{ common_pid: bash [ 8710] } hitcount: 3 count: 66369
|
|
{ common_pid: dbus-daemon-lau [ 8703] } hitcount: 49 count: 47739
|
|
{ common_pid: irqbalance [ 1252] } hitcount: 27 count: 27648
|
|
{ common_pid: 01ifupdown [ 8705] } hitcount: 3 count: 17216
|
|
{ common_pid: dbus-daemon [ 772] } hitcount: 10 count: 12396
|
|
{ common_pid: Socket Thread [ 8342] } hitcount: 11 count: 11264
|
|
{ common_pid: nm-dhcp-client. [ 8701] } hitcount: 6 count: 7424
|
|
{ common_pid: gmain [ 1315] } hitcount: 18 count: 6336
|
|
.
|
|
.
|
|
.
|
|
{ common_pid: postgres [ 1892] } hitcount: 2 count: 32
|
|
{ common_pid: postgres [ 1891] } hitcount: 2 count: 32
|
|
{ common_pid: gmain [ 8704] } hitcount: 2 count: 32
|
|
{ common_pid: upstart-dbus-br [ 2740] } hitcount: 21 count: 21
|
|
{ common_pid: nm-dispatcher.a [ 8696] } hitcount: 1 count: 16
|
|
{ common_pid: indicator-datet [ 2904] } hitcount: 1 count: 16
|
|
{ common_pid: gdbus [ 2998] } hitcount: 1 count: 16
|
|
{ common_pid: rtkit-daemon [ 2052] } hitcount: 1 count: 8
|
|
{ common_pid: init [ 1] } hitcount: 2 count: 2
|
|
|
|
Totals:
|
|
Hits: 2116
|
|
Entries: 51
|
|
Dropped: 0
|
|
|
|
Similarly, if you key a hist trigger on syscall id, for example to
|
|
gather and display a list of systemwide syscall hits, you can use
|
|
the special .syscall modifier to display the syscall names rather
|
|
than raw ids. The example below keeps a running total of syscall
|
|
counts for the system during the run::
|
|
|
|
# echo 'hist:key=id.syscall:val=hitcount' > \
|
|
/sys/kernel/debug/tracing/events/raw_syscalls/sys_enter/trigger
|
|
|
|
# cat /sys/kernel/debug/tracing/events/raw_syscalls/sys_enter/hist
|
|
# trigger info: hist:keys=id.syscall:vals=hitcount:sort=hitcount:size=2048 [active]
|
|
|
|
{ id: sys_fsync [ 74] } hitcount: 1
|
|
{ id: sys_newuname [ 63] } hitcount: 1
|
|
{ id: sys_prctl [157] } hitcount: 1
|
|
{ id: sys_statfs [137] } hitcount: 1
|
|
{ id: sys_symlink [ 88] } hitcount: 1
|
|
{ id: sys_sendmmsg [307] } hitcount: 1
|
|
{ id: sys_semctl [ 66] } hitcount: 1
|
|
{ id: sys_readlink [ 89] } hitcount: 3
|
|
{ id: sys_bind [ 49] } hitcount: 3
|
|
{ id: sys_getsockname [ 51] } hitcount: 3
|
|
{ id: sys_unlink [ 87] } hitcount: 3
|
|
{ id: sys_rename [ 82] } hitcount: 4
|
|
{ id: unknown_syscall [ 58] } hitcount: 4
|
|
{ id: sys_connect [ 42] } hitcount: 4
|
|
{ id: sys_getpid [ 39] } hitcount: 4
|
|
.
|
|
.
|
|
.
|
|
{ id: sys_rt_sigprocmask [ 14] } hitcount: 952
|
|
{ id: sys_futex [202] } hitcount: 1534
|
|
{ id: sys_write [ 1] } hitcount: 2689
|
|
{ id: sys_setitimer [ 38] } hitcount: 2797
|
|
{ id: sys_read [ 0] } hitcount: 3202
|
|
{ id: sys_select [ 23] } hitcount: 3773
|
|
{ id: sys_writev [ 20] } hitcount: 4531
|
|
{ id: sys_poll [ 7] } hitcount: 8314
|
|
{ id: sys_recvmsg [ 47] } hitcount: 13738
|
|
{ id: sys_ioctl [ 16] } hitcount: 21843
|
|
|
|
Totals:
|
|
Hits: 67612
|
|
Entries: 72
|
|
Dropped: 0
|
|
|
|
The syscall counts above provide a rough overall picture of system
|
|
call activity on the system; we can see for example that the most
|
|
popular system call on this system was the 'sys_ioctl' system call.
|
|
|
|
We can use 'compound' keys to refine that number and provide some
|
|
further insight as to which processes exactly contribute to the
|
|
overall ioctl count.
|
|
|
|
The command below keeps a hitcount for every unique combination of
|
|
system call id and pid - the end result is essentially a table
|
|
that keeps a per-pid sum of system call hits. The results are
|
|
sorted using the system call id as the primary key, and the
|
|
hitcount sum as the secondary key::
|
|
|
|
# echo 'hist:key=id.syscall,common_pid.execname:val=hitcount:sort=id,hitcount' > \
|
|
/sys/kernel/debug/tracing/events/raw_syscalls/sys_enter/trigger
|
|
|
|
# cat /sys/kernel/debug/tracing/events/raw_syscalls/sys_enter/hist
|
|
# trigger info: hist:keys=id.syscall,common_pid.execname:vals=hitcount:sort=id.syscall,hitcount:size=2048 [active]
|
|
|
|
{ id: sys_read [ 0], common_pid: rtkit-daemon [ 1877] } hitcount: 1
|
|
{ id: sys_read [ 0], common_pid: gdbus [ 2976] } hitcount: 1
|
|
{ id: sys_read [ 0], common_pid: console-kit-dae [ 3400] } hitcount: 1
|
|
{ id: sys_read [ 0], common_pid: postgres [ 1865] } hitcount: 1
|
|
{ id: sys_read [ 0], common_pid: deja-dup-monito [ 3543] } hitcount: 2
|
|
{ id: sys_read [ 0], common_pid: NetworkManager [ 890] } hitcount: 2
|
|
{ id: sys_read [ 0], common_pid: evolution-calen [ 3048] } hitcount: 2
|
|
{ id: sys_read [ 0], common_pid: postgres [ 1864] } hitcount: 2
|
|
{ id: sys_read [ 0], common_pid: nm-applet [ 3022] } hitcount: 2
|
|
{ id: sys_read [ 0], common_pid: whoopsie [ 1212] } hitcount: 2
|
|
.
|
|
.
|
|
.
|
|
{ id: sys_ioctl [ 16], common_pid: bash [ 8479] } hitcount: 1
|
|
{ id: sys_ioctl [ 16], common_pid: bash [ 3472] } hitcount: 12
|
|
{ id: sys_ioctl [ 16], common_pid: gnome-terminal [ 3199] } hitcount: 16
|
|
{ id: sys_ioctl [ 16], common_pid: Xorg [ 1267] } hitcount: 1808
|
|
{ id: sys_ioctl [ 16], common_pid: compiz [ 2994] } hitcount: 5580
|
|
.
|
|
.
|
|
.
|
|
{ id: sys_waitid [247], common_pid: upstart-dbus-br [ 2690] } hitcount: 3
|
|
{ id: sys_waitid [247], common_pid: upstart-dbus-br [ 2688] } hitcount: 16
|
|
{ id: sys_inotify_add_watch [254], common_pid: gmain [ 975] } hitcount: 2
|
|
{ id: sys_inotify_add_watch [254], common_pid: gmain [ 3204] } hitcount: 4
|
|
{ id: sys_inotify_add_watch [254], common_pid: gmain [ 2888] } hitcount: 4
|
|
{ id: sys_inotify_add_watch [254], common_pid: gmain [ 3003] } hitcount: 4
|
|
{ id: sys_inotify_add_watch [254], common_pid: gmain [ 2873] } hitcount: 4
|
|
{ id: sys_inotify_add_watch [254], common_pid: gmain [ 3196] } hitcount: 6
|
|
{ id: sys_openat [257], common_pid: java [ 2623] } hitcount: 2
|
|
{ id: sys_eventfd2 [290], common_pid: ibus-ui-gtk3 [ 2760] } hitcount: 4
|
|
{ id: sys_eventfd2 [290], common_pid: compiz [ 2994] } hitcount: 6
|
|
|
|
Totals:
|
|
Hits: 31536
|
|
Entries: 323
|
|
Dropped: 0
|
|
|
|
The above list does give us a breakdown of the ioctl syscall by
|
|
pid, but it also gives us quite a bit more than that, which we
|
|
don't really care about at the moment. Since we know the syscall
|
|
id for sys_ioctl (16, displayed next to the sys_ioctl name), we
|
|
can use that to filter out all the other syscalls::
|
|
|
|
# echo 'hist:key=id.syscall,common_pid.execname:val=hitcount:sort=id,hitcount if id == 16' > \
|
|
/sys/kernel/debug/tracing/events/raw_syscalls/sys_enter/trigger
|
|
|
|
# cat /sys/kernel/debug/tracing/events/raw_syscalls/sys_enter/hist
|
|
# trigger info: hist:keys=id.syscall,common_pid.execname:vals=hitcount:sort=id.syscall,hitcount:size=2048 if id == 16 [active]
|
|
|
|
{ id: sys_ioctl [ 16], common_pid: gmain [ 2769] } hitcount: 1
|
|
{ id: sys_ioctl [ 16], common_pid: evolution-addre [ 8571] } hitcount: 1
|
|
{ id: sys_ioctl [ 16], common_pid: gmain [ 3003] } hitcount: 1
|
|
{ id: sys_ioctl [ 16], common_pid: gmain [ 2781] } hitcount: 1
|
|
{ id: sys_ioctl [ 16], common_pid: gmain [ 2829] } hitcount: 1
|
|
{ id: sys_ioctl [ 16], common_pid: bash [ 8726] } hitcount: 1
|
|
{ id: sys_ioctl [ 16], common_pid: bash [ 8508] } hitcount: 1
|
|
{ id: sys_ioctl [ 16], common_pid: gmain [ 2970] } hitcount: 1
|
|
{ id: sys_ioctl [ 16], common_pid: gmain [ 2768] } hitcount: 1
|
|
.
|
|
.
|
|
.
|
|
{ id: sys_ioctl [ 16], common_pid: pool [ 8559] } hitcount: 45
|
|
{ id: sys_ioctl [ 16], common_pid: pool [ 8555] } hitcount: 48
|
|
{ id: sys_ioctl [ 16], common_pid: pool [ 8551] } hitcount: 48
|
|
{ id: sys_ioctl [ 16], common_pid: avahi-daemon [ 896] } hitcount: 66
|
|
{ id: sys_ioctl [ 16], common_pid: Xorg [ 1267] } hitcount: 26674
|
|
{ id: sys_ioctl [ 16], common_pid: compiz [ 2994] } hitcount: 73443
|
|
|
|
Totals:
|
|
Hits: 101162
|
|
Entries: 103
|
|
Dropped: 0
|
|
|
|
The above output shows that 'compiz' and 'Xorg' are far and away
|
|
the heaviest ioctl callers (which might lead to questions about
|
|
whether they really need to be making all those calls and to
|
|
possible avenues for further investigation.)
|
|
|
|
The compound key examples used a key and a sum value (hitcount) to
|
|
sort the output, but we can just as easily use two keys instead.
|
|
Here's an example where we use a compound key composed of the the
|
|
common_pid and size event fields. Sorting with pid as the primary
|
|
key and 'size' as the secondary key allows us to display an
|
|
ordered summary of the recvfrom sizes, with counts, received by
|
|
each process::
|
|
|
|
# echo 'hist:key=common_pid.execname,size:val=hitcount:sort=common_pid,size' > \
|
|
/sys/kernel/debug/tracing/events/syscalls/sys_enter_recvfrom/trigger
|
|
|
|
# cat /sys/kernel/debug/tracing/events/syscalls/sys_enter_recvfrom/hist
|
|
# trigger info: hist:keys=common_pid.execname,size:vals=hitcount:sort=common_pid.execname,size:size=2048 [active]
|
|
|
|
{ common_pid: smbd [ 784], size: 4 } hitcount: 1
|
|
{ common_pid: dnsmasq [ 1412], size: 4096 } hitcount: 672
|
|
{ common_pid: postgres [ 1796], size: 1000 } hitcount: 6
|
|
{ common_pid: postgres [ 1867], size: 1000 } hitcount: 10
|
|
{ common_pid: bamfdaemon [ 2787], size: 28 } hitcount: 2
|
|
{ common_pid: bamfdaemon [ 2787], size: 14360 } hitcount: 1
|
|
{ common_pid: compiz [ 2994], size: 8 } hitcount: 1
|
|
{ common_pid: compiz [ 2994], size: 20 } hitcount: 11
|
|
{ common_pid: gnome-terminal [ 3199], size: 4 } hitcount: 2
|
|
{ common_pid: firefox [ 8817], size: 4 } hitcount: 1
|
|
{ common_pid: firefox [ 8817], size: 8 } hitcount: 5
|
|
{ common_pid: firefox [ 8817], size: 588 } hitcount: 2
|
|
{ common_pid: firefox [ 8817], size: 628 } hitcount: 1
|
|
{ common_pid: firefox [ 8817], size: 6944 } hitcount: 1
|
|
{ common_pid: firefox [ 8817], size: 408880 } hitcount: 2
|
|
{ common_pid: firefox [ 8822], size: 8 } hitcount: 2
|
|
{ common_pid: firefox [ 8822], size: 160 } hitcount: 2
|
|
{ common_pid: firefox [ 8822], size: 320 } hitcount: 2
|
|
{ common_pid: firefox [ 8822], size: 352 } hitcount: 1
|
|
.
|
|
.
|
|
.
|
|
{ common_pid: pool [ 8923], size: 1960 } hitcount: 10
|
|
{ common_pid: pool [ 8923], size: 2048 } hitcount: 10
|
|
{ common_pid: pool [ 8924], size: 1960 } hitcount: 10
|
|
{ common_pid: pool [ 8924], size: 2048 } hitcount: 10
|
|
{ common_pid: pool [ 8928], size: 1964 } hitcount: 4
|
|
{ common_pid: pool [ 8928], size: 1965 } hitcount: 2
|
|
{ common_pid: pool [ 8928], size: 2048 } hitcount: 6
|
|
{ common_pid: pool [ 8929], size: 1982 } hitcount: 1
|
|
{ common_pid: pool [ 8929], size: 2048 } hitcount: 1
|
|
|
|
Totals:
|
|
Hits: 2016
|
|
Entries: 224
|
|
Dropped: 0
|
|
|
|
The above example also illustrates the fact that although a compound
|
|
key is treated as a single entity for hashing purposes, the sub-keys
|
|
it's composed of can be accessed independently.
|
|
|
|
The next example uses a string field as the hash key and
|
|
demonstrates how you can manually pause and continue a hist trigger.
|
|
In this example, we'll aggregate fork counts and don't expect a
|
|
large number of entries in the hash table, so we'll drop it to a
|
|
much smaller number, say 256::
|
|
|
|
# echo 'hist:key=child_comm:val=hitcount:size=256' > \
|
|
/sys/kernel/debug/tracing/events/sched/sched_process_fork/trigger
|
|
|
|
# cat /sys/kernel/debug/tracing/events/sched/sched_process_fork/hist
|
|
# trigger info: hist:keys=child_comm:vals=hitcount:sort=hitcount:size=256 [active]
|
|
|
|
{ child_comm: dconf worker } hitcount: 1
|
|
{ child_comm: ibus-daemon } hitcount: 1
|
|
{ child_comm: whoopsie } hitcount: 1
|
|
{ child_comm: smbd } hitcount: 1
|
|
{ child_comm: gdbus } hitcount: 1
|
|
{ child_comm: kthreadd } hitcount: 1
|
|
{ child_comm: dconf worker } hitcount: 1
|
|
{ child_comm: evolution-alarm } hitcount: 2
|
|
{ child_comm: Socket Thread } hitcount: 2
|
|
{ child_comm: postgres } hitcount: 2
|
|
{ child_comm: bash } hitcount: 3
|
|
{ child_comm: compiz } hitcount: 3
|
|
{ child_comm: evolution-sourc } hitcount: 4
|
|
{ child_comm: dhclient } hitcount: 4
|
|
{ child_comm: pool } hitcount: 5
|
|
{ child_comm: nm-dispatcher.a } hitcount: 8
|
|
{ child_comm: firefox } hitcount: 8
|
|
{ child_comm: dbus-daemon } hitcount: 8
|
|
{ child_comm: glib-pacrunner } hitcount: 10
|
|
{ child_comm: evolution } hitcount: 23
|
|
|
|
Totals:
|
|
Hits: 89
|
|
Entries: 20
|
|
Dropped: 0
|
|
|
|
If we want to pause the hist trigger, we can simply append :pause to
|
|
the command that started the trigger. Notice that the trigger info
|
|
displays as [paused]::
|
|
|
|
# echo 'hist:key=child_comm:val=hitcount:size=256:pause' >> \
|
|
/sys/kernel/debug/tracing/events/sched/sched_process_fork/trigger
|
|
|
|
# cat /sys/kernel/debug/tracing/events/sched/sched_process_fork/hist
|
|
# trigger info: hist:keys=child_comm:vals=hitcount:sort=hitcount:size=256 [paused]
|
|
|
|
{ child_comm: dconf worker } hitcount: 1
|
|
{ child_comm: kthreadd } hitcount: 1
|
|
{ child_comm: dconf worker } hitcount: 1
|
|
{ child_comm: gdbus } hitcount: 1
|
|
{ child_comm: ibus-daemon } hitcount: 1
|
|
{ child_comm: Socket Thread } hitcount: 2
|
|
{ child_comm: evolution-alarm } hitcount: 2
|
|
{ child_comm: smbd } hitcount: 2
|
|
{ child_comm: bash } hitcount: 3
|
|
{ child_comm: whoopsie } hitcount: 3
|
|
{ child_comm: compiz } hitcount: 3
|
|
{ child_comm: evolution-sourc } hitcount: 4
|
|
{ child_comm: pool } hitcount: 5
|
|
{ child_comm: postgres } hitcount: 6
|
|
{ child_comm: firefox } hitcount: 8
|
|
{ child_comm: dhclient } hitcount: 10
|
|
{ child_comm: emacs } hitcount: 12
|
|
{ child_comm: dbus-daemon } hitcount: 20
|
|
{ child_comm: nm-dispatcher.a } hitcount: 20
|
|
{ child_comm: evolution } hitcount: 35
|
|
{ child_comm: glib-pacrunner } hitcount: 59
|
|
|
|
Totals:
|
|
Hits: 199
|
|
Entries: 21
|
|
Dropped: 0
|
|
|
|
To manually continue having the trigger aggregate events, append
|
|
:cont instead. Notice that the trigger info displays as [active]
|
|
again, and the data has changed::
|
|
|
|
# echo 'hist:key=child_comm:val=hitcount:size=256:cont' >> \
|
|
/sys/kernel/debug/tracing/events/sched/sched_process_fork/trigger
|
|
|
|
# cat /sys/kernel/debug/tracing/events/sched/sched_process_fork/hist
|
|
# trigger info: hist:keys=child_comm:vals=hitcount:sort=hitcount:size=256 [active]
|
|
|
|
{ child_comm: dconf worker } hitcount: 1
|
|
{ child_comm: dconf worker } hitcount: 1
|
|
{ child_comm: kthreadd } hitcount: 1
|
|
{ child_comm: gdbus } hitcount: 1
|
|
{ child_comm: ibus-daemon } hitcount: 1
|
|
{ child_comm: Socket Thread } hitcount: 2
|
|
{ child_comm: evolution-alarm } hitcount: 2
|
|
{ child_comm: smbd } hitcount: 2
|
|
{ child_comm: whoopsie } hitcount: 3
|
|
{ child_comm: compiz } hitcount: 3
|
|
{ child_comm: evolution-sourc } hitcount: 4
|
|
{ child_comm: bash } hitcount: 5
|
|
{ child_comm: pool } hitcount: 5
|
|
{ child_comm: postgres } hitcount: 6
|
|
{ child_comm: firefox } hitcount: 8
|
|
{ child_comm: dhclient } hitcount: 11
|
|
{ child_comm: emacs } hitcount: 12
|
|
{ child_comm: dbus-daemon } hitcount: 22
|
|
{ child_comm: nm-dispatcher.a } hitcount: 22
|
|
{ child_comm: evolution } hitcount: 35
|
|
{ child_comm: glib-pacrunner } hitcount: 59
|
|
|
|
Totals:
|
|
Hits: 206
|
|
Entries: 21
|
|
Dropped: 0
|
|
|
|
The previous example showed how to start and stop a hist trigger by
|
|
appending 'pause' and 'continue' to the hist trigger command. A
|
|
hist trigger can also be started in a paused state by initially
|
|
starting the trigger with ':pause' appended. This allows you to
|
|
start the trigger only when you're ready to start collecting data
|
|
and not before. For example, you could start the trigger in a
|
|
paused state, then unpause it and do something you want to measure,
|
|
then pause the trigger again when done.
|
|
|
|
Of course, doing this manually can be difficult and error-prone, but
|
|
it is possible to automatically start and stop a hist trigger based
|
|
on some condition, via the enable_hist and disable_hist triggers.
|
|
|
|
For example, suppose we wanted to take a look at the relative
|
|
weights in terms of skb length for each callpath that leads to a
|
|
netif_receieve_skb event when downloading a decent-sized file using
|
|
wget.
|
|
|
|
First we set up an initially paused stacktrace trigger on the
|
|
netif_receive_skb event::
|
|
|
|
# echo 'hist:key=stacktrace:vals=len:pause' > \
|
|
/sys/kernel/debug/tracing/events/net/netif_receive_skb/trigger
|
|
|
|
Next, we set up an 'enable_hist' trigger on the sched_process_exec
|
|
event, with an 'if filename==/usr/bin/wget' filter. The effect of
|
|
this new trigger is that it will 'unpause' the hist trigger we just
|
|
set up on netif_receive_skb if and only if it sees a
|
|
sched_process_exec event with a filename of '/usr/bin/wget'. When
|
|
that happens, all netif_receive_skb events are aggregated into a
|
|
hash table keyed on stacktrace::
|
|
|
|
# echo 'enable_hist:net:netif_receive_skb if filename==/usr/bin/wget' > \
|
|
/sys/kernel/debug/tracing/events/sched/sched_process_exec/trigger
|
|
|
|
The aggregation continues until the netif_receive_skb is paused
|
|
again, which is what the following disable_hist event does by
|
|
creating a similar setup on the sched_process_exit event, using the
|
|
filter 'comm==wget'::
|
|
|
|
# echo 'disable_hist:net:netif_receive_skb if comm==wget' > \
|
|
/sys/kernel/debug/tracing/events/sched/sched_process_exit/trigger
|
|
|
|
Whenever a process exits and the comm field of the disable_hist
|
|
trigger filter matches 'comm==wget', the netif_receive_skb hist
|
|
trigger is disabled.
|
|
|
|
The overall effect is that netif_receive_skb events are aggregated
|
|
into the hash table for only the duration of the wget. Executing a
|
|
wget command and then listing the 'hist' file will display the
|
|
output generated by the wget command::
|
|
|
|
$ wget https://www.kernel.org/pub/linux/kernel/v3.x/patch-3.19.xz
|
|
|
|
# cat /sys/kernel/debug/tracing/events/net/netif_receive_skb/hist
|
|
# trigger info: hist:keys=stacktrace:vals=len:sort=hitcount:size=2048 [paused]
|
|
|
|
{ stacktrace:
|
|
__netif_receive_skb_core+0x46d/0x990
|
|
__netif_receive_skb+0x18/0x60
|
|
netif_receive_skb_internal+0x23/0x90
|
|
napi_gro_receive+0xc8/0x100
|
|
ieee80211_deliver_skb+0xd6/0x270 [mac80211]
|
|
ieee80211_rx_handlers+0xccf/0x22f0 [mac80211]
|
|
ieee80211_prepare_and_rx_handle+0x4e7/0xc40 [mac80211]
|
|
ieee80211_rx+0x31d/0x900 [mac80211]
|
|
iwlagn_rx_reply_rx+0x3db/0x6f0 [iwldvm]
|
|
iwl_rx_dispatch+0x8e/0xf0 [iwldvm]
|
|
iwl_pcie_irq_handler+0xe3c/0x12f0 [iwlwifi]
|
|
irq_thread_fn+0x20/0x50
|
|
irq_thread+0x11f/0x150
|
|
kthread+0xd2/0xf0
|
|
ret_from_fork+0x42/0x70
|
|
} hitcount: 85 len: 28884
|
|
{ stacktrace:
|
|
__netif_receive_skb_core+0x46d/0x990
|
|
__netif_receive_skb+0x18/0x60
|
|
netif_receive_skb_internal+0x23/0x90
|
|
napi_gro_complete+0xa4/0xe0
|
|
dev_gro_receive+0x23a/0x360
|
|
napi_gro_receive+0x30/0x100
|
|
ieee80211_deliver_skb+0xd6/0x270 [mac80211]
|
|
ieee80211_rx_handlers+0xccf/0x22f0 [mac80211]
|
|
ieee80211_prepare_and_rx_handle+0x4e7/0xc40 [mac80211]
|
|
ieee80211_rx+0x31d/0x900 [mac80211]
|
|
iwlagn_rx_reply_rx+0x3db/0x6f0 [iwldvm]
|
|
iwl_rx_dispatch+0x8e/0xf0 [iwldvm]
|
|
iwl_pcie_irq_handler+0xe3c/0x12f0 [iwlwifi]
|
|
irq_thread_fn+0x20/0x50
|
|
irq_thread+0x11f/0x150
|
|
kthread+0xd2/0xf0
|
|
} hitcount: 98 len: 664329
|
|
{ stacktrace:
|
|
__netif_receive_skb_core+0x46d/0x990
|
|
__netif_receive_skb+0x18/0x60
|
|
process_backlog+0xa8/0x150
|
|
net_rx_action+0x15d/0x340
|
|
__do_softirq+0x114/0x2c0
|
|
do_softirq_own_stack+0x1c/0x30
|
|
do_softirq+0x65/0x70
|
|
__local_bh_enable_ip+0xb5/0xc0
|
|
ip_finish_output+0x1f4/0x840
|
|
ip_output+0x6b/0xc0
|
|
ip_local_out_sk+0x31/0x40
|
|
ip_send_skb+0x1a/0x50
|
|
udp_send_skb+0x173/0x2a0
|
|
udp_sendmsg+0x2bf/0x9f0
|
|
inet_sendmsg+0x64/0xa0
|
|
sock_sendmsg+0x3d/0x50
|
|
} hitcount: 115 len: 13030
|
|
{ stacktrace:
|
|
__netif_receive_skb_core+0x46d/0x990
|
|
__netif_receive_skb+0x18/0x60
|
|
netif_receive_skb_internal+0x23/0x90
|
|
napi_gro_complete+0xa4/0xe0
|
|
napi_gro_flush+0x6d/0x90
|
|
iwl_pcie_irq_handler+0x92a/0x12f0 [iwlwifi]
|
|
irq_thread_fn+0x20/0x50
|
|
irq_thread+0x11f/0x150
|
|
kthread+0xd2/0xf0
|
|
ret_from_fork+0x42/0x70
|
|
} hitcount: 934 len: 5512212
|
|
|
|
Totals:
|
|
Hits: 1232
|
|
Entries: 4
|
|
Dropped: 0
|
|
|
|
The above shows all the netif_receive_skb callpaths and their total
|
|
lengths for the duration of the wget command.
|
|
|
|
The 'clear' hist trigger param can be used to clear the hash table.
|
|
Suppose we wanted to try another run of the previous example but
|
|
this time also wanted to see the complete list of events that went
|
|
into the histogram. In order to avoid having to set everything up
|
|
again, we can just clear the histogram first::
|
|
|
|
# echo 'hist:key=stacktrace:vals=len:clear' >> \
|
|
/sys/kernel/debug/tracing/events/net/netif_receive_skb/trigger
|
|
|
|
Just to verify that it is in fact cleared, here's what we now see in
|
|
the hist file::
|
|
|
|
# cat /sys/kernel/debug/tracing/events/net/netif_receive_skb/hist
|
|
# trigger info: hist:keys=stacktrace:vals=len:sort=hitcount:size=2048 [paused]
|
|
|
|
Totals:
|
|
Hits: 0
|
|
Entries: 0
|
|
Dropped: 0
|
|
|
|
Since we want to see the detailed list of every netif_receive_skb
|
|
event occurring during the new run, which are in fact the same
|
|
events being aggregated into the hash table, we add some additional
|
|
'enable_event' events to the triggering sched_process_exec and
|
|
sched_process_exit events as such::
|
|
|
|
# echo 'enable_event:net:netif_receive_skb if filename==/usr/bin/wget' > \
|
|
/sys/kernel/debug/tracing/events/sched/sched_process_exec/trigger
|
|
|
|
# echo 'disable_event:net:netif_receive_skb if comm==wget' > \
|
|
/sys/kernel/debug/tracing/events/sched/sched_process_exit/trigger
|
|
|
|
If you read the trigger files for the sched_process_exec and
|
|
sched_process_exit triggers, you should see two triggers for each:
|
|
one enabling/disabling the hist aggregation and the other
|
|
enabling/disabling the logging of events::
|
|
|
|
# cat /sys/kernel/debug/tracing/events/sched/sched_process_exec/trigger
|
|
enable_event:net:netif_receive_skb:unlimited if filename==/usr/bin/wget
|
|
enable_hist:net:netif_receive_skb:unlimited if filename==/usr/bin/wget
|
|
|
|
# cat /sys/kernel/debug/tracing/events/sched/sched_process_exit/trigger
|
|
enable_event:net:netif_receive_skb:unlimited if comm==wget
|
|
disable_hist:net:netif_receive_skb:unlimited if comm==wget
|
|
|
|
In other words, whenever either of the sched_process_exec or
|
|
sched_process_exit events is hit and matches 'wget', it enables or
|
|
disables both the histogram and the event log, and what you end up
|
|
with is a hash table and set of events just covering the specified
|
|
duration. Run the wget command again::
|
|
|
|
$ wget https://www.kernel.org/pub/linux/kernel/v3.x/patch-3.19.xz
|
|
|
|
Displaying the 'hist' file should show something similar to what you
|
|
saw in the last run, but this time you should also see the
|
|
individual events in the trace file::
|
|
|
|
# cat /sys/kernel/debug/tracing/trace
|
|
|
|
# tracer: nop
|
|
#
|
|
# entries-in-buffer/entries-written: 183/1426 #P:4
|
|
#
|
|
# _-----=> irqs-off
|
|
# / _----=> need-resched
|
|
# | / _---=> hardirq/softirq
|
|
# || / _--=> preempt-depth
|
|
# ||| / delay
|
|
# TASK-PID CPU# |||| TIMESTAMP FUNCTION
|
|
# | | | |||| | |
|
|
wget-15108 [000] ..s1 31769.606929: netif_receive_skb: dev=lo skbaddr=ffff88009c353100 len=60
|
|
wget-15108 [000] ..s1 31769.606999: netif_receive_skb: dev=lo skbaddr=ffff88009c353200 len=60
|
|
dnsmasq-1382 [000] ..s1 31769.677652: netif_receive_skb: dev=lo skbaddr=ffff88009c352b00 len=130
|
|
dnsmasq-1382 [000] ..s1 31769.685917: netif_receive_skb: dev=lo skbaddr=ffff88009c352200 len=138
|
|
##### CPU 2 buffer started ####
|
|
irq/29-iwlwifi-559 [002] ..s. 31772.031529: netif_receive_skb: dev=wlan0 skbaddr=ffff88009d433d00 len=2948
|
|
irq/29-iwlwifi-559 [002] ..s. 31772.031572: netif_receive_skb: dev=wlan0 skbaddr=ffff88009d432200 len=1500
|
|
irq/29-iwlwifi-559 [002] ..s. 31772.032196: netif_receive_skb: dev=wlan0 skbaddr=ffff88009d433100 len=2948
|
|
irq/29-iwlwifi-559 [002] ..s. 31772.032761: netif_receive_skb: dev=wlan0 skbaddr=ffff88009d433000 len=2948
|
|
irq/29-iwlwifi-559 [002] ..s. 31772.033220: netif_receive_skb: dev=wlan0 skbaddr=ffff88009d432e00 len=1500
|
|
.
|
|
.
|
|
.
|
|
|
|
The following example demonstrates how multiple hist triggers can be
|
|
attached to a given event. This capability can be useful for
|
|
creating a set of different summaries derived from the same set of
|
|
events, or for comparing the effects of different filters, among
|
|
other things::
|
|
|
|
# echo 'hist:keys=skbaddr.hex:vals=len if len < 0' >> \
|
|
/sys/kernel/debug/tracing/events/net/netif_receive_skb/trigger
|
|
# echo 'hist:keys=skbaddr.hex:vals=len if len > 4096' >> \
|
|
/sys/kernel/debug/tracing/events/net/netif_receive_skb/trigger
|
|
# echo 'hist:keys=skbaddr.hex:vals=len if len == 256' >> \
|
|
/sys/kernel/debug/tracing/events/net/netif_receive_skb/trigger
|
|
# echo 'hist:keys=skbaddr.hex:vals=len' >> \
|
|
/sys/kernel/debug/tracing/events/net/netif_receive_skb/trigger
|
|
# echo 'hist:keys=len:vals=common_preempt_count' >> \
|
|
/sys/kernel/debug/tracing/events/net/netif_receive_skb/trigger
|
|
|
|
The above set of commands create four triggers differing only in
|
|
their filters, along with a completely different though fairly
|
|
nonsensical trigger. Note that in order to append multiple hist
|
|
triggers to the same file, you should use the '>>' operator to
|
|
append them ('>' will also add the new hist trigger, but will remove
|
|
any existing hist triggers beforehand).
|
|
|
|
Displaying the contents of the 'hist' file for the event shows the
|
|
contents of all five histograms::
|
|
|
|
# cat /sys/kernel/debug/tracing/events/net/netif_receive_skb/hist
|
|
|
|
# event histogram
|
|
#
|
|
# trigger info: hist:keys=len:vals=hitcount,common_preempt_count:sort=hitcount:size=2048 [active]
|
|
#
|
|
|
|
{ len: 176 } hitcount: 1 common_preempt_count: 0
|
|
{ len: 223 } hitcount: 1 common_preempt_count: 0
|
|
{ len: 4854 } hitcount: 1 common_preempt_count: 0
|
|
{ len: 395 } hitcount: 1 common_preempt_count: 0
|
|
{ len: 177 } hitcount: 1 common_preempt_count: 0
|
|
{ len: 446 } hitcount: 1 common_preempt_count: 0
|
|
{ len: 1601 } hitcount: 1 common_preempt_count: 0
|
|
.
|
|
.
|
|
.
|
|
{ len: 1280 } hitcount: 66 common_preempt_count: 0
|
|
{ len: 116 } hitcount: 81 common_preempt_count: 40
|
|
{ len: 708 } hitcount: 112 common_preempt_count: 0
|
|
{ len: 46 } hitcount: 221 common_preempt_count: 0
|
|
{ len: 1264 } hitcount: 458 common_preempt_count: 0
|
|
|
|
Totals:
|
|
Hits: 1428
|
|
Entries: 147
|
|
Dropped: 0
|
|
|
|
|
|
# event histogram
|
|
#
|
|
# trigger info: hist:keys=skbaddr.hex:vals=hitcount,len:sort=hitcount:size=2048 [active]
|
|
#
|
|
|
|
{ skbaddr: ffff8800baee5e00 } hitcount: 1 len: 130
|
|
{ skbaddr: ffff88005f3d5600 } hitcount: 1 len: 1280
|
|
{ skbaddr: ffff88005f3d4900 } hitcount: 1 len: 1280
|
|
{ skbaddr: ffff88009fed6300 } hitcount: 1 len: 115
|
|
{ skbaddr: ffff88009fe0ad00 } hitcount: 1 len: 115
|
|
{ skbaddr: ffff88008cdb1900 } hitcount: 1 len: 46
|
|
{ skbaddr: ffff880064b5ef00 } hitcount: 1 len: 118
|
|
{ skbaddr: ffff880044e3c700 } hitcount: 1 len: 60
|
|
{ skbaddr: ffff880100065900 } hitcount: 1 len: 46
|
|
{ skbaddr: ffff8800d46bd500 } hitcount: 1 len: 116
|
|
{ skbaddr: ffff88005f3d5f00 } hitcount: 1 len: 1280
|
|
{ skbaddr: ffff880100064700 } hitcount: 1 len: 365
|
|
{ skbaddr: ffff8800badb6f00 } hitcount: 1 len: 60
|
|
.
|
|
.
|
|
.
|
|
{ skbaddr: ffff88009fe0be00 } hitcount: 27 len: 24677
|
|
{ skbaddr: ffff88009fe0a400 } hitcount: 27 len: 23052
|
|
{ skbaddr: ffff88009fe0b700 } hitcount: 31 len: 25589
|
|
{ skbaddr: ffff88009fe0b600 } hitcount: 32 len: 27326
|
|
{ skbaddr: ffff88006a462800 } hitcount: 68 len: 71678
|
|
{ skbaddr: ffff88006a463700 } hitcount: 70 len: 72678
|
|
{ skbaddr: ffff88006a462b00 } hitcount: 71 len: 77589
|
|
{ skbaddr: ffff88006a463600 } hitcount: 73 len: 71307
|
|
{ skbaddr: ffff88006a462200 } hitcount: 81 len: 81032
|
|
|
|
Totals:
|
|
Hits: 1451
|
|
Entries: 318
|
|
Dropped: 0
|
|
|
|
|
|
# event histogram
|
|
#
|
|
# trigger info: hist:keys=skbaddr.hex:vals=hitcount,len:sort=hitcount:size=2048 if len == 256 [active]
|
|
#
|
|
|
|
|
|
Totals:
|
|
Hits: 0
|
|
Entries: 0
|
|
Dropped: 0
|
|
|
|
|
|
# event histogram
|
|
#
|
|
# trigger info: hist:keys=skbaddr.hex:vals=hitcount,len:sort=hitcount:size=2048 if len > 4096 [active]
|
|
#
|
|
|
|
{ skbaddr: ffff88009fd2c300 } hitcount: 1 len: 7212
|
|
{ skbaddr: ffff8800d2bcce00 } hitcount: 1 len: 7212
|
|
{ skbaddr: ffff8800d2bcd700 } hitcount: 1 len: 7212
|
|
{ skbaddr: ffff8800d2bcda00 } hitcount: 1 len: 21492
|
|
{ skbaddr: ffff8800ae2e2d00 } hitcount: 1 len: 7212
|
|
{ skbaddr: ffff8800d2bcdb00 } hitcount: 1 len: 7212
|
|
{ skbaddr: ffff88006a4df500 } hitcount: 1 len: 4854
|
|
{ skbaddr: ffff88008ce47b00 } hitcount: 1 len: 18636
|
|
{ skbaddr: ffff8800ae2e2200 } hitcount: 1 len: 12924
|
|
{ skbaddr: ffff88005f3e1000 } hitcount: 1 len: 4356
|
|
{ skbaddr: ffff8800d2bcdc00 } hitcount: 2 len: 24420
|
|
{ skbaddr: ffff8800d2bcc200 } hitcount: 2 len: 12996
|
|
|
|
Totals:
|
|
Hits: 14
|
|
Entries: 12
|
|
Dropped: 0
|
|
|
|
|
|
# event histogram
|
|
#
|
|
# trigger info: hist:keys=skbaddr.hex:vals=hitcount,len:sort=hitcount:size=2048 if len < 0 [active]
|
|
#
|
|
|
|
|
|
Totals:
|
|
Hits: 0
|
|
Entries: 0
|
|
Dropped: 0
|
|
|
|
Named triggers can be used to have triggers share a common set of
|
|
histogram data. This capability is mostly useful for combining the
|
|
output of events generated by tracepoints contained inside inline
|
|
functions, but names can be used in a hist trigger on any event.
|
|
For example, these two triggers when hit will update the same 'len'
|
|
field in the shared 'foo' histogram data::
|
|
|
|
# echo 'hist:name=foo:keys=skbaddr.hex:vals=len' > \
|
|
/sys/kernel/debug/tracing/events/net/netif_receive_skb/trigger
|
|
# echo 'hist:name=foo:keys=skbaddr.hex:vals=len' > \
|
|
/sys/kernel/debug/tracing/events/net/netif_rx/trigger
|
|
|
|
You can see that they're updating common histogram data by reading
|
|
each event's hist files at the same time::
|
|
|
|
# cat /sys/kernel/debug/tracing/events/net/netif_receive_skb/hist;
|
|
cat /sys/kernel/debug/tracing/events/net/netif_rx/hist
|
|
|
|
# event histogram
|
|
#
|
|
# trigger info: hist:name=foo:keys=skbaddr.hex:vals=hitcount,len:sort=hitcount:size=2048 [active]
|
|
#
|
|
|
|
{ skbaddr: ffff88000ad53500 } hitcount: 1 len: 46
|
|
{ skbaddr: ffff8800af5a1500 } hitcount: 1 len: 76
|
|
{ skbaddr: ffff8800d62a1900 } hitcount: 1 len: 46
|
|
{ skbaddr: ffff8800d2bccb00 } hitcount: 1 len: 468
|
|
{ skbaddr: ffff8800d3c69900 } hitcount: 1 len: 46
|
|
{ skbaddr: ffff88009ff09100 } hitcount: 1 len: 52
|
|
{ skbaddr: ffff88010f13ab00 } hitcount: 1 len: 168
|
|
{ skbaddr: ffff88006a54f400 } hitcount: 1 len: 46
|
|
{ skbaddr: ffff8800d2bcc500 } hitcount: 1 len: 260
|
|
{ skbaddr: ffff880064505000 } hitcount: 1 len: 46
|
|
{ skbaddr: ffff8800baf24e00 } hitcount: 1 len: 32
|
|
{ skbaddr: ffff88009fe0ad00 } hitcount: 1 len: 46
|
|
{ skbaddr: ffff8800d3edff00 } hitcount: 1 len: 44
|
|
{ skbaddr: ffff88009fe0b400 } hitcount: 1 len: 168
|
|
{ skbaddr: ffff8800a1c55a00 } hitcount: 1 len: 40
|
|
{ skbaddr: ffff8800d2bcd100 } hitcount: 1 len: 40
|
|
{ skbaddr: ffff880064505f00 } hitcount: 1 len: 174
|
|
{ skbaddr: ffff8800a8bff200 } hitcount: 1 len: 160
|
|
{ skbaddr: ffff880044e3cc00 } hitcount: 1 len: 76
|
|
{ skbaddr: ffff8800a8bfe700 } hitcount: 1 len: 46
|
|
{ skbaddr: ffff8800d2bcdc00 } hitcount: 1 len: 32
|
|
{ skbaddr: ffff8800a1f64800 } hitcount: 1 len: 46
|
|
{ skbaddr: ffff8800d2bcde00 } hitcount: 1 len: 988
|
|
{ skbaddr: ffff88006a5dea00 } hitcount: 1 len: 46
|
|
{ skbaddr: ffff88002e37a200 } hitcount: 1 len: 44
|
|
{ skbaddr: ffff8800a1f32c00 } hitcount: 2 len: 676
|
|
{ skbaddr: ffff88000ad52600 } hitcount: 2 len: 107
|
|
{ skbaddr: ffff8800a1f91e00 } hitcount: 2 len: 92
|
|
{ skbaddr: ffff8800af5a0200 } hitcount: 2 len: 142
|
|
{ skbaddr: ffff8800d2bcc600 } hitcount: 2 len: 220
|
|
{ skbaddr: ffff8800ba36f500 } hitcount: 2 len: 92
|
|
{ skbaddr: ffff8800d021f800 } hitcount: 2 len: 92
|
|
{ skbaddr: ffff8800a1f33600 } hitcount: 2 len: 675
|
|
{ skbaddr: ffff8800a8bfff00 } hitcount: 3 len: 138
|
|
{ skbaddr: ffff8800d62a1300 } hitcount: 3 len: 138
|
|
{ skbaddr: ffff88002e37a100 } hitcount: 4 len: 184
|
|
{ skbaddr: ffff880064504400 } hitcount: 4 len: 184
|
|
{ skbaddr: ffff8800a8bfec00 } hitcount: 4 len: 184
|
|
{ skbaddr: ffff88000ad53700 } hitcount: 5 len: 230
|
|
{ skbaddr: ffff8800d2bcdb00 } hitcount: 5 len: 196
|
|
{ skbaddr: ffff8800a1f90000 } hitcount: 6 len: 276
|
|
{ skbaddr: ffff88006a54f900 } hitcount: 6 len: 276
|
|
|
|
Totals:
|
|
Hits: 81
|
|
Entries: 42
|
|
Dropped: 0
|
|
# event histogram
|
|
#
|
|
# trigger info: hist:name=foo:keys=skbaddr.hex:vals=hitcount,len:sort=hitcount:size=2048 [active]
|
|
#
|
|
|
|
{ skbaddr: ffff88000ad53500 } hitcount: 1 len: 46
|
|
{ skbaddr: ffff8800af5a1500 } hitcount: 1 len: 76
|
|
{ skbaddr: ffff8800d62a1900 } hitcount: 1 len: 46
|
|
{ skbaddr: ffff8800d2bccb00 } hitcount: 1 len: 468
|
|
{ skbaddr: ffff8800d3c69900 } hitcount: 1 len: 46
|
|
{ skbaddr: ffff88009ff09100 } hitcount: 1 len: 52
|
|
{ skbaddr: ffff88010f13ab00 } hitcount: 1 len: 168
|
|
{ skbaddr: ffff88006a54f400 } hitcount: 1 len: 46
|
|
{ skbaddr: ffff8800d2bcc500 } hitcount: 1 len: 260
|
|
{ skbaddr: ffff880064505000 } hitcount: 1 len: 46
|
|
{ skbaddr: ffff8800baf24e00 } hitcount: 1 len: 32
|
|
{ skbaddr: ffff88009fe0ad00 } hitcount: 1 len: 46
|
|
{ skbaddr: ffff8800d3edff00 } hitcount: 1 len: 44
|
|
{ skbaddr: ffff88009fe0b400 } hitcount: 1 len: 168
|
|
{ skbaddr: ffff8800a1c55a00 } hitcount: 1 len: 40
|
|
{ skbaddr: ffff8800d2bcd100 } hitcount: 1 len: 40
|
|
{ skbaddr: ffff880064505f00 } hitcount: 1 len: 174
|
|
{ skbaddr: ffff8800a8bff200 } hitcount: 1 len: 160
|
|
{ skbaddr: ffff880044e3cc00 } hitcount: 1 len: 76
|
|
{ skbaddr: ffff8800a8bfe700 } hitcount: 1 len: 46
|
|
{ skbaddr: ffff8800d2bcdc00 } hitcount: 1 len: 32
|
|
{ skbaddr: ffff8800a1f64800 } hitcount: 1 len: 46
|
|
{ skbaddr: ffff8800d2bcde00 } hitcount: 1 len: 988
|
|
{ skbaddr: ffff88006a5dea00 } hitcount: 1 len: 46
|
|
{ skbaddr: ffff88002e37a200 } hitcount: 1 len: 44
|
|
{ skbaddr: ffff8800a1f32c00 } hitcount: 2 len: 676
|
|
{ skbaddr: ffff88000ad52600 } hitcount: 2 len: 107
|
|
{ skbaddr: ffff8800a1f91e00 } hitcount: 2 len: 92
|
|
{ skbaddr: ffff8800af5a0200 } hitcount: 2 len: 142
|
|
{ skbaddr: ffff8800d2bcc600 } hitcount: 2 len: 220
|
|
{ skbaddr: ffff8800ba36f500 } hitcount: 2 len: 92
|
|
{ skbaddr: ffff8800d021f800 } hitcount: 2 len: 92
|
|
{ skbaddr: ffff8800a1f33600 } hitcount: 2 len: 675
|
|
{ skbaddr: ffff8800a8bfff00 } hitcount: 3 len: 138
|
|
{ skbaddr: ffff8800d62a1300 } hitcount: 3 len: 138
|
|
{ skbaddr: ffff88002e37a100 } hitcount: 4 len: 184
|
|
{ skbaddr: ffff880064504400 } hitcount: 4 len: 184
|
|
{ skbaddr: ffff8800a8bfec00 } hitcount: 4 len: 184
|
|
{ skbaddr: ffff88000ad53700 } hitcount: 5 len: 230
|
|
{ skbaddr: ffff8800d2bcdb00 } hitcount: 5 len: 196
|
|
{ skbaddr: ffff8800a1f90000 } hitcount: 6 len: 276
|
|
{ skbaddr: ffff88006a54f900 } hitcount: 6 len: 276
|
|
|
|
Totals:
|
|
Hits: 81
|
|
Entries: 42
|
|
Dropped: 0
|
|
|
|
And here's an example that shows how to combine histogram data from
|
|
any two events even if they don't share any 'compatible' fields
|
|
other than 'hitcount' and 'stacktrace'. These commands create a
|
|
couple of triggers named 'bar' using those fields::
|
|
|
|
# echo 'hist:name=bar:key=stacktrace:val=hitcount' > \
|
|
/sys/kernel/debug/tracing/events/sched/sched_process_fork/trigger
|
|
# echo 'hist:name=bar:key=stacktrace:val=hitcount' > \
|
|
/sys/kernel/debug/tracing/events/net/netif_rx/trigger
|
|
|
|
And displaying the output of either shows some interesting if
|
|
somewhat confusing output::
|
|
|
|
# cat /sys/kernel/debug/tracing/events/sched/sched_process_fork/hist
|
|
# cat /sys/kernel/debug/tracing/events/net/netif_rx/hist
|
|
|
|
# event histogram
|
|
#
|
|
# trigger info: hist:name=bar:keys=stacktrace:vals=hitcount:sort=hitcount:size=2048 [active]
|
|
#
|
|
|
|
{ stacktrace:
|
|
_do_fork+0x18e/0x330
|
|
kernel_thread+0x29/0x30
|
|
kthreadd+0x154/0x1b0
|
|
ret_from_fork+0x3f/0x70
|
|
} hitcount: 1
|
|
{ stacktrace:
|
|
netif_rx_internal+0xb2/0xd0
|
|
netif_rx_ni+0x20/0x70
|
|
dev_loopback_xmit+0xaa/0xd0
|
|
ip_mc_output+0x126/0x240
|
|
ip_local_out_sk+0x31/0x40
|
|
igmp_send_report+0x1e9/0x230
|
|
igmp_timer_expire+0xe9/0x120
|
|
call_timer_fn+0x39/0xf0
|
|
run_timer_softirq+0x1e1/0x290
|
|
__do_softirq+0xfd/0x290
|
|
irq_exit+0x98/0xb0
|
|
smp_apic_timer_interrupt+0x4a/0x60
|
|
apic_timer_interrupt+0x6d/0x80
|
|
cpuidle_enter+0x17/0x20
|
|
call_cpuidle+0x3b/0x60
|
|
cpu_startup_entry+0x22d/0x310
|
|
} hitcount: 1
|
|
{ stacktrace:
|
|
netif_rx_internal+0xb2/0xd0
|
|
netif_rx_ni+0x20/0x70
|
|
dev_loopback_xmit+0xaa/0xd0
|
|
ip_mc_output+0x17f/0x240
|
|
ip_local_out_sk+0x31/0x40
|
|
ip_send_skb+0x1a/0x50
|
|
udp_send_skb+0x13e/0x270
|
|
udp_sendmsg+0x2bf/0x980
|
|
inet_sendmsg+0x67/0xa0
|
|
sock_sendmsg+0x38/0x50
|
|
SYSC_sendto+0xef/0x170
|
|
SyS_sendto+0xe/0x10
|
|
entry_SYSCALL_64_fastpath+0x12/0x6a
|
|
} hitcount: 2
|
|
{ stacktrace:
|
|
netif_rx_internal+0xb2/0xd0
|
|
netif_rx+0x1c/0x60
|
|
loopback_xmit+0x6c/0xb0
|
|
dev_hard_start_xmit+0x219/0x3a0
|
|
__dev_queue_xmit+0x415/0x4f0
|
|
dev_queue_xmit_sk+0x13/0x20
|
|
ip_finish_output2+0x237/0x340
|
|
ip_finish_output+0x113/0x1d0
|
|
ip_output+0x66/0xc0
|
|
ip_local_out_sk+0x31/0x40
|
|
ip_send_skb+0x1a/0x50
|
|
udp_send_skb+0x16d/0x270
|
|
udp_sendmsg+0x2bf/0x980
|
|
inet_sendmsg+0x67/0xa0
|
|
sock_sendmsg+0x38/0x50
|
|
___sys_sendmsg+0x14e/0x270
|
|
} hitcount: 76
|
|
{ stacktrace:
|
|
netif_rx_internal+0xb2/0xd0
|
|
netif_rx+0x1c/0x60
|
|
loopback_xmit+0x6c/0xb0
|
|
dev_hard_start_xmit+0x219/0x3a0
|
|
__dev_queue_xmit+0x415/0x4f0
|
|
dev_queue_xmit_sk+0x13/0x20
|
|
ip_finish_output2+0x237/0x340
|
|
ip_finish_output+0x113/0x1d0
|
|
ip_output+0x66/0xc0
|
|
ip_local_out_sk+0x31/0x40
|
|
ip_send_skb+0x1a/0x50
|
|
udp_send_skb+0x16d/0x270
|
|
udp_sendmsg+0x2bf/0x980
|
|
inet_sendmsg+0x67/0xa0
|
|
sock_sendmsg+0x38/0x50
|
|
___sys_sendmsg+0x269/0x270
|
|
} hitcount: 77
|
|
{ stacktrace:
|
|
netif_rx_internal+0xb2/0xd0
|
|
netif_rx+0x1c/0x60
|
|
loopback_xmit+0x6c/0xb0
|
|
dev_hard_start_xmit+0x219/0x3a0
|
|
__dev_queue_xmit+0x415/0x4f0
|
|
dev_queue_xmit_sk+0x13/0x20
|
|
ip_finish_output2+0x237/0x340
|
|
ip_finish_output+0x113/0x1d0
|
|
ip_output+0x66/0xc0
|
|
ip_local_out_sk+0x31/0x40
|
|
ip_send_skb+0x1a/0x50
|
|
udp_send_skb+0x16d/0x270
|
|
udp_sendmsg+0x2bf/0x980
|
|
inet_sendmsg+0x67/0xa0
|
|
sock_sendmsg+0x38/0x50
|
|
SYSC_sendto+0xef/0x170
|
|
} hitcount: 88
|
|
{ stacktrace:
|
|
_do_fork+0x18e/0x330
|
|
SyS_clone+0x19/0x20
|
|
entry_SYSCALL_64_fastpath+0x12/0x6a
|
|
} hitcount: 244
|
|
|
|
Totals:
|
|
Hits: 489
|
|
Entries: 7
|
|
Dropped: 0
|
|
|
|
2.2 Inter-event hist triggers
|
|
-----------------------------
|
|
|
|
Inter-event hist triggers are hist triggers that combine values from
|
|
one or more other events and create a histogram using that data. Data
|
|
from an inter-event histogram can in turn become the source for
|
|
further combined histograms, thus providing a chain of related
|
|
histograms, which is important for some applications.
|
|
|
|
The most important example of an inter-event quantity that can be used
|
|
in this manner is latency, which is simply a difference in timestamps
|
|
between two events. Although latency is the most important
|
|
inter-event quantity, note that because the support is completely
|
|
general across the trace event subsystem, any event field can be used
|
|
in an inter-event quantity.
|
|
|
|
An example of a histogram that combines data from other histograms
|
|
into a useful chain would be a 'wakeupswitch latency' histogram that
|
|
combines a 'wakeup latency' histogram and a 'switch latency'
|
|
histogram.
|
|
|
|
Normally, a hist trigger specification consists of a (possibly
|
|
compound) key along with one or more numeric values, which are
|
|
continually updated sums associated with that key. A histogram
|
|
specification in this case consists of individual key and value
|
|
specifications that refer to trace event fields associated with a
|
|
single event type.
|
|
|
|
The inter-event hist trigger extension allows fields from multiple
|
|
events to be referenced and combined into a multi-event histogram
|
|
specification. In support of this overall goal, a few enabling
|
|
features have been added to the hist trigger support:
|
|
|
|
- In order to compute an inter-event quantity, a value from one
|
|
event needs to saved and then referenced from another event. This
|
|
requires the introduction of support for histogram 'variables'.
|
|
|
|
- The computation of inter-event quantities and their combination
|
|
require some minimal amount of support for applying simple
|
|
expressions to variables (+ and -).
|
|
|
|
- A histogram consisting of inter-event quantities isn't logically a
|
|
histogram on either event (so having the 'hist' file for either
|
|
event host the histogram output doesn't really make sense). To
|
|
address the idea that the histogram is associated with a
|
|
combination of events, support is added allowing the creation of
|
|
'synthetic' events that are events derived from other events.
|
|
These synthetic events are full-fledged events just like any other
|
|
and can be used as such, as for instance to create the
|
|
'combination' histograms mentioned previously.
|
|
|
|
- A set of 'actions' can be associated with histogram entries -
|
|
these can be used to generate the previously mentioned synthetic
|
|
events, but can also be used for other purposes, such as for
|
|
example saving context when a 'max' latency has been hit.
|
|
|
|
- Trace events don't have a 'timestamp' associated with them, but
|
|
there is an implicit timestamp saved along with an event in the
|
|
underlying ftrace ring buffer. This timestamp is now exposed as a
|
|
a synthetic field named 'common_timestamp' which can be used in
|
|
histograms as if it were any other event field; it isn't an actual
|
|
field in the trace format but rather is a synthesized value that
|
|
nonetheless can be used as if it were an actual field. By default
|
|
it is in units of nanoseconds; appending '.usecs' to a
|
|
common_timestamp field changes the units to microseconds.
|
|
|
|
A note on inter-event timestamps: If common_timestamp is used in a
|
|
histogram, the trace buffer is automatically switched over to using
|
|
absolute timestamps and the "global" trace clock, in order to avoid
|
|
bogus timestamp differences with other clocks that aren't coherent
|
|
across CPUs. This can be overridden by specifying one of the other
|
|
trace clocks instead, using the "clock=XXX" hist trigger attribute,
|
|
where XXX is any of the clocks listed in the tracing/trace_clock
|
|
pseudo-file.
|
|
|
|
These features are described in more detail in the following sections.
|
|
|
|
2.2.1 Histogram Variables
|
|
-------------------------
|
|
|
|
Variables are simply named locations used for saving and retrieving
|
|
values between matching events. A 'matching' event is defined as an
|
|
event that has a matching key - if a variable is saved for a histogram
|
|
entry corresponding to that key, any subsequent event with a matching
|
|
key can access that variable.
|
|
|
|
A variable's value is normally available to any subsequent event until
|
|
it is set to something else by a subsequent event. The one exception
|
|
to that rule is that any variable used in an expression is essentially
|
|
'read-once' - once it's used by an expression in a subsequent event,
|
|
it's reset to its 'unset' state, which means it can't be used again
|
|
unless it's set again. This ensures not only that an event doesn't
|
|
use an uninitialized variable in a calculation, but that that variable
|
|
is used only once and not for any unrelated subsequent match.
|
|
|
|
The basic syntax for saving a variable is to simply prefix a unique
|
|
variable name not corresponding to any keyword along with an '=' sign
|
|
to any event field.
|
|
|
|
Either keys or values can be saved and retrieved in this way. This
|
|
creates a variable named 'ts0' for a histogram entry with the key
|
|
'next_pid'::
|
|
|
|
# echo 'hist:keys=next_pid:vals=$ts0:ts0=common_timestamp ... >> \
|
|
event/trigger
|
|
|
|
The ts0 variable can be accessed by any subsequent event having the
|
|
same pid as 'next_pid'.
|
|
|
|
Variable references are formed by prepending the variable name with
|
|
the '$' sign. Thus for example, the ts0 variable above would be
|
|
referenced as '$ts0' in expressions.
|
|
|
|
Because 'vals=' is used, the common_timestamp variable value above
|
|
will also be summed as a normal histogram value would (though for a
|
|
timestamp it makes little sense).
|
|
|
|
The below shows that a key value can also be saved in the same way::
|
|
|
|
# echo 'hist:timer_pid=common_pid:key=timer_pid ...' >> event/trigger
|
|
|
|
If a variable isn't a key variable or prefixed with 'vals=', the
|
|
associated event field will be saved in a variable but won't be summed
|
|
as a value::
|
|
|
|
# echo 'hist:keys=next_pid:ts1=common_timestamp ...' >> event/trigger
|
|
|
|
Multiple variables can be assigned at the same time. The below would
|
|
result in both ts0 and b being created as variables, with both
|
|
common_timestamp and field1 additionally being summed as values::
|
|
|
|
# echo 'hist:keys=pid:vals=$ts0,$b:ts0=common_timestamp,b=field1 ...' >> \
|
|
event/trigger
|
|
|
|
Note that variable assignments can appear either preceding or
|
|
following their use. The command below behaves identically to the
|
|
command above::
|
|
|
|
# echo 'hist:keys=pid:ts0=common_timestamp,b=field1:vals=$ts0,$b ...' >> \
|
|
event/trigger
|
|
|
|
Any number of variables not bound to a 'vals=' prefix can also be
|
|
assigned by simply separating them with colons. Below is the same
|
|
thing but without the values being summed in the histogram::
|
|
|
|
# echo 'hist:keys=pid:ts0=common_timestamp:b=field1 ...' >> event/trigger
|
|
|
|
Variables set as above can be referenced and used in expressions on
|
|
another event.
|
|
|
|
For example, here's how a latency can be calculated::
|
|
|
|
# echo 'hist:keys=pid,prio:ts0=common_timestamp ...' >> event1/trigger
|
|
# echo 'hist:keys=next_pid:wakeup_lat=common_timestamp-$ts0 ...' >> event2/trigger
|
|
|
|
In the first line above, the event's timetamp is saved into the
|
|
variable ts0. In the next line, ts0 is subtracted from the second
|
|
event's timestamp to produce the latency, which is then assigned into
|
|
yet another variable, 'wakeup_lat'. The hist trigger below in turn
|
|
makes use of the wakeup_lat variable to compute a combined latency
|
|
using the same key and variable from yet another event::
|
|
|
|
# echo 'hist:key=pid:wakeupswitch_lat=$wakeup_lat+$switchtime_lat ...' >> event3/trigger
|
|
|
|
2.2.2 Synthetic Events
|
|
----------------------
|
|
|
|
Synthetic events are user-defined events generated from hist trigger
|
|
variables or fields associated with one or more other events. Their
|
|
purpose is to provide a mechanism for displaying data spanning
|
|
multiple events consistent with the existing and already familiar
|
|
usage for normal events.
|
|
|
|
To define a synthetic event, the user writes a simple specification
|
|
consisting of the name of the new event along with one or more
|
|
variables and their types, which can be any valid field type,
|
|
separated by semicolons, to the tracing/synthetic_events file.
|
|
|
|
For instance, the following creates a new event named 'wakeup_latency'
|
|
with 3 fields: lat, pid, and prio. Each of those fields is simply a
|
|
variable reference to a variable on another event::
|
|
|
|
# echo 'wakeup_latency \
|
|
u64 lat; \
|
|
pid_t pid; \
|
|
int prio' >> \
|
|
/sys/kernel/debug/tracing/synthetic_events
|
|
|
|
Reading the tracing/synthetic_events file lists all the currently
|
|
defined synthetic events, in this case the event defined above::
|
|
|
|
# cat /sys/kernel/debug/tracing/synthetic_events
|
|
wakeup_latency u64 lat; pid_t pid; int prio
|
|
|
|
An existing synthetic event definition can be removed by prepending
|
|
the command that defined it with a '!'::
|
|
|
|
# echo '!wakeup_latency u64 lat pid_t pid int prio' >> \
|
|
/sys/kernel/debug/tracing/synthetic_events
|
|
|
|
At this point, there isn't yet an actual 'wakeup_latency' event
|
|
instantiated in the event subsytem - for this to happen, a 'hist
|
|
trigger action' needs to be instantiated and bound to actual fields
|
|
and variables defined on other events (see Section 2.2.3 below on
|
|
how that is done using hist trigger 'onmatch' action). Once that is
|
|
done, the 'wakeup_latency' synthetic event instance is created.
|
|
|
|
A histogram can now be defined for the new synthetic event::
|
|
|
|
# echo 'hist:keys=pid,prio,lat.log2:sort=pid,lat' >> \
|
|
/sys/kernel/debug/tracing/events/synthetic/wakeup_latency/trigger
|
|
|
|
The new event is created under the tracing/events/synthetic/ directory
|
|
and looks and behaves just like any other event::
|
|
|
|
# ls /sys/kernel/debug/tracing/events/synthetic/wakeup_latency
|
|
enable filter format hist id trigger
|
|
|
|
Like any other event, once a histogram is enabled for the event, the
|
|
output can be displayed by reading the event's 'hist' file.
|
|
|
|
2.2.3 Hist trigger 'actions'
|
|
----------------------------
|
|
|
|
A hist trigger 'action' is a function that's executed whenever a
|
|
histogram entry is added or updated.
|
|
|
|
The default 'action' if no special function is explicity specified is
|
|
as it always has been, to simply update the set of values associated
|
|
with an entry. Some applications, however, may want to perform
|
|
additional actions at that point, such as generate another event, or
|
|
compare and save a maximum.
|
|
|
|
The following additional actions are available. To specify an action
|
|
for a given event, simply specify the action between colons in the
|
|
hist trigger specification.
|
|
|
|
- onmatch(matching.event).<synthetic_event_name>(param list)
|
|
|
|
The 'onmatch(matching.event).<synthetic_event_name>(params)' hist
|
|
trigger action is invoked whenever an event matches and the
|
|
histogram entry would be added or updated. It causes the named
|
|
synthetic event to be generated with the values given in the
|
|
'param list'. The result is the generation of a synthetic event
|
|
that consists of the values contained in those variables at the
|
|
time the invoking event was hit.
|
|
|
|
The 'param list' consists of one or more parameters which may be
|
|
either variables or fields defined on either the 'matching.event'
|
|
or the target event. The variables or fields specified in the
|
|
param list may be either fully-qualified or unqualified. If a
|
|
variable is specified as unqualified, it must be unique between
|
|
the two events. A field name used as a param can be unqualified
|
|
if it refers to the target event, but must be fully qualified if
|
|
it refers to the matching event. A fully-qualified name is of the
|
|
form 'system.event_name.$var_name' or 'system.event_name.field'.
|
|
|
|
The 'matching.event' specification is simply the fully qualified
|
|
event name of the event that matches the target event for the
|
|
onmatch() functionality, in the form 'system.event_name'.
|
|
|
|
Finally, the number and type of variables/fields in the 'param
|
|
list' must match the number and types of the fields in the
|
|
synthetic event being generated.
|
|
|
|
As an example the below defines a simple synthetic event and uses
|
|
a variable defined on the sched_wakeup_new event as a parameter
|
|
when invoking the synthetic event. Here we define the synthetic
|
|
event::
|
|
|
|
# echo 'wakeup_new_test pid_t pid' >> \
|
|
/sys/kernel/debug/tracing/synthetic_events
|
|
|
|
# cat /sys/kernel/debug/tracing/synthetic_events
|
|
wakeup_new_test pid_t pid
|
|
|
|
The following hist trigger both defines the missing testpid
|
|
variable and specifies an onmatch() action that generates a
|
|
wakeup_new_test synthetic event whenever a sched_wakeup_new event
|
|
occurs, which because of the 'if comm == "cyclictest"' filter only
|
|
happens when the executable is cyclictest::
|
|
|
|
# echo 'hist:keys=$testpid:testpid=pid:onmatch(sched.sched_wakeup_new).\
|
|
wakeup_new_test($testpid) if comm=="cyclictest"' >> \
|
|
/sys/kernel/debug/tracing/events/sched/sched_wakeup_new/trigger
|
|
|
|
Creating and displaying a histogram based on those events is now
|
|
just a matter of using the fields and new synthetic event in the
|
|
tracing/events/synthetic directory, as usual::
|
|
|
|
# echo 'hist:keys=pid:sort=pid' >> \
|
|
/sys/kernel/debug/tracing/events/synthetic/wakeup_new_test/trigger
|
|
|
|
Running 'cyclictest' should cause wakeup_new events to generate
|
|
wakeup_new_test synthetic events which should result in histogram
|
|
output in the wakeup_new_test event's hist file::
|
|
|
|
# cat /sys/kernel/debug/tracing/events/synthetic/wakeup_new_test/hist
|
|
|
|
A more typical usage would be to use two events to calculate a
|
|
latency. The following example uses a set of hist triggers to
|
|
produce a 'wakeup_latency' histogram.
|
|
|
|
First, we define a 'wakeup_latency' synthetic event::
|
|
|
|
# echo 'wakeup_latency u64 lat; pid_t pid; int prio' >> \
|
|
/sys/kernel/debug/tracing/synthetic_events
|
|
|
|
Next, we specify that whenever we see a sched_waking event for a
|
|
cyclictest thread, save the timestamp in a 'ts0' variable::
|
|
|
|
# echo 'hist:keys=$saved_pid:saved_pid=pid:ts0=common_timestamp.usecs \
|
|
if comm=="cyclictest"' >> \
|
|
/sys/kernel/debug/tracing/events/sched/sched_waking/trigger
|
|
|
|
Then, when the corresponding thread is actually scheduled onto the
|
|
CPU by a sched_switch event, calculate the latency and use that
|
|
along with another variable and an event field to generate a
|
|
wakeup_latency synthetic event::
|
|
|
|
# echo 'hist:keys=next_pid:wakeup_lat=common_timestamp.usecs-$ts0:\
|
|
onmatch(sched.sched_waking).wakeup_latency($wakeup_lat,\
|
|
$saved_pid,next_prio) if next_comm=="cyclictest"' >> \
|
|
/sys/kernel/debug/tracing/events/sched/sched_switch/trigger
|
|
|
|
We also need to create a histogram on the wakeup_latency synthetic
|
|
event in order to aggregate the generated synthetic event data::
|
|
|
|
# echo 'hist:keys=pid,prio,lat:sort=pid,lat' >> \
|
|
/sys/kernel/debug/tracing/events/synthetic/wakeup_latency/trigger
|
|
|
|
Finally, once we've run cyclictest to actually generate some
|
|
events, we can see the output by looking at the wakeup_latency
|
|
synthetic event's hist file::
|
|
|
|
# cat /sys/kernel/debug/tracing/events/synthetic/wakeup_latency/hist
|
|
|
|
- onmax(var).save(field,.. .)
|
|
|
|
The 'onmax(var).save(field,...)' hist trigger action is invoked
|
|
whenever the value of 'var' associated with a histogram entry
|
|
exceeds the current maximum contained in that variable.
|
|
|
|
The end result is that the trace event fields specified as the
|
|
onmax.save() params will be saved if 'var' exceeds the current
|
|
maximum for that hist trigger entry. This allows context from the
|
|
event that exhibited the new maximum to be saved for later
|
|
reference. When the histogram is displayed, additional fields
|
|
displaying the saved values will be printed.
|
|
|
|
As an example the below defines a couple of hist triggers, one for
|
|
sched_waking and another for sched_switch, keyed on pid. Whenever
|
|
a sched_waking occurs, the timestamp is saved in the entry
|
|
corresponding to the current pid, and when the scheduler switches
|
|
back to that pid, the timestamp difference is calculated. If the
|
|
resulting latency, stored in wakeup_lat, exceeds the current
|
|
maximum latency, the values specified in the save() fields are
|
|
recorded::
|
|
|
|
# echo 'hist:keys=pid:ts0=common_timestamp.usecs \
|
|
if comm=="cyclictest"' >> \
|
|
/sys/kernel/debug/tracing/events/sched/sched_waking/trigger
|
|
|
|
# echo 'hist:keys=next_pid:\
|
|
wakeup_lat=common_timestamp.usecs-$ts0:\
|
|
onmax($wakeup_lat).save(next_comm,prev_pid,prev_prio,prev_comm) \
|
|
if next_comm=="cyclictest"' >> \
|
|
/sys/kernel/debug/tracing/events/sched/sched_switch/trigger
|
|
|
|
When the histogram is displayed, the max value and the saved
|
|
values corresponding to the max are displayed following the rest
|
|
of the fields::
|
|
|
|
# cat /sys/kernel/debug/tracing/events/sched/sched_switch/hist
|
|
{ next_pid: 2255 } hitcount: 239
|
|
common_timestamp-ts0: 0
|
|
max: 27
|
|
next_comm: cyclictest
|
|
prev_pid: 0 prev_prio: 120 prev_comm: swapper/1
|
|
|
|
{ next_pid: 2256 } hitcount: 2355
|
|
common_timestamp-ts0: 0
|
|
max: 49 next_comm: cyclictest
|
|
prev_pid: 0 prev_prio: 120 prev_comm: swapper/0
|
|
|
|
Totals:
|
|
Hits: 12970
|
|
Entries: 2
|
|
Dropped: 0
|
|
|
|
3. User space creating a trigger
|
|
--------------------------------
|
|
|
|
Writing into /sys/kernel/tracing/trace_marker writes into the ftrace
|
|
ring buffer. This can also act like an event, by writing into the trigger
|
|
file located in /sys/kernel/tracing/events/ftrace/print/
|
|
|
|
Modifying cyclictest to write into the trace_marker file before it sleeps
|
|
and after it wakes up, something like this::
|
|
|
|
static void traceputs(char *str)
|
|
{
|
|
/* tracemark_fd is the trace_marker file descriptor */
|
|
if (tracemark_fd < 0)
|
|
return;
|
|
/* write the tracemark message */
|
|
write(tracemark_fd, str, strlen(str));
|
|
}
|
|
|
|
And later add something like::
|
|
|
|
traceputs("start");
|
|
clock_nanosleep(...);
|
|
traceputs("end");
|
|
|
|
We can make a histogram from this::
|
|
|
|
# cd /sys/kernel/tracing
|
|
# echo 'latency u64 lat' > synthetic_events
|
|
# echo 'hist:keys=common_pid:ts0=common_timestamp.usecs if buf == "start"' > events/ftrace/print/trigger
|
|
# echo 'hist:keys=common_pid:lat=common_timestamp.usecs-$ts0:onmatch(ftrace.print).latency($lat) if buf == "end"' >> events/ftrace/print/trigger
|
|
# echo 'hist:keys=lat,common_pid:sort=lat' > events/synthetic/latency/trigger
|
|
|
|
The above created a synthetic event called "latency" and two histograms
|
|
against the trace_marker, one gets triggered when "start" is written into the
|
|
trace_marker file and the other when "end" is written. If the pids match, then
|
|
it will call the "latency" synthetic event with the calculated latency as its
|
|
parameter. Finally, a histogram is added to the latency synthetic event to
|
|
record the calculated latency along with the pid.
|
|
|
|
Now running cyclictest with::
|
|
|
|
# ./cyclictest -p80 -d0 -i250 -n -a -t --tracemark -b 1000
|
|
|
|
-p80 : run threads at priority 80
|
|
-d0 : have all threads run at the same interval
|
|
-i250 : start the interval at 250 microseconds (all threads will do this)
|
|
-n : sleep with nanosleep
|
|
-a : affine all threads to a separate CPU
|
|
-t : one thread per available CPU
|
|
--tracemark : enable trace mark writing
|
|
-b 1000 : stop if any latency is greater than 1000 microseconds
|
|
|
|
Note, the -b 1000 is used just to make --tracemark available.
|
|
|
|
Then we can see the histogram created by this with::
|
|
|
|
# cat events/synthetic/latency/hist
|
|
# event histogram
|
|
#
|
|
# trigger info: hist:keys=lat,common_pid:vals=hitcount:sort=lat:size=2048 [active]
|
|
#
|
|
|
|
{ lat: 107, common_pid: 2039 } hitcount: 1
|
|
{ lat: 122, common_pid: 2041 } hitcount: 1
|
|
{ lat: 166, common_pid: 2039 } hitcount: 1
|
|
{ lat: 174, common_pid: 2039 } hitcount: 1
|
|
{ lat: 194, common_pid: 2041 } hitcount: 1
|
|
{ lat: 196, common_pid: 2036 } hitcount: 1
|
|
{ lat: 197, common_pid: 2038 } hitcount: 1
|
|
{ lat: 198, common_pid: 2039 } hitcount: 1
|
|
{ lat: 199, common_pid: 2039 } hitcount: 1
|
|
{ lat: 200, common_pid: 2041 } hitcount: 1
|
|
{ lat: 201, common_pid: 2039 } hitcount: 2
|
|
{ lat: 202, common_pid: 2038 } hitcount: 1
|
|
{ lat: 202, common_pid: 2043 } hitcount: 1
|
|
{ lat: 203, common_pid: 2039 } hitcount: 1
|
|
{ lat: 203, common_pid: 2036 } hitcount: 1
|
|
{ lat: 203, common_pid: 2041 } hitcount: 1
|
|
{ lat: 206, common_pid: 2038 } hitcount: 2
|
|
{ lat: 207, common_pid: 2039 } hitcount: 1
|
|
{ lat: 207, common_pid: 2036 } hitcount: 1
|
|
{ lat: 208, common_pid: 2040 } hitcount: 1
|
|
{ lat: 209, common_pid: 2043 } hitcount: 1
|
|
{ lat: 210, common_pid: 2039 } hitcount: 1
|
|
{ lat: 211, common_pid: 2039 } hitcount: 4
|
|
{ lat: 212, common_pid: 2043 } hitcount: 1
|
|
{ lat: 212, common_pid: 2039 } hitcount: 2
|
|
{ lat: 213, common_pid: 2039 } hitcount: 1
|
|
{ lat: 214, common_pid: 2038 } hitcount: 1
|
|
{ lat: 214, common_pid: 2039 } hitcount: 2
|
|
{ lat: 214, common_pid: 2042 } hitcount: 1
|
|
{ lat: 215, common_pid: 2039 } hitcount: 1
|
|
{ lat: 217, common_pid: 2036 } hitcount: 1
|
|
{ lat: 217, common_pid: 2040 } hitcount: 1
|
|
{ lat: 217, common_pid: 2039 } hitcount: 1
|
|
{ lat: 218, common_pid: 2039 } hitcount: 6
|
|
{ lat: 219, common_pid: 2039 } hitcount: 9
|
|
{ lat: 220, common_pid: 2039 } hitcount: 11
|
|
{ lat: 221, common_pid: 2039 } hitcount: 5
|
|
{ lat: 221, common_pid: 2042 } hitcount: 1
|
|
{ lat: 222, common_pid: 2039 } hitcount: 7
|
|
{ lat: 223, common_pid: 2036 } hitcount: 1
|
|
{ lat: 223, common_pid: 2039 } hitcount: 3
|
|
{ lat: 224, common_pid: 2039 } hitcount: 4
|
|
{ lat: 224, common_pid: 2037 } hitcount: 1
|
|
{ lat: 224, common_pid: 2036 } hitcount: 2
|
|
{ lat: 225, common_pid: 2039 } hitcount: 5
|
|
{ lat: 225, common_pid: 2042 } hitcount: 1
|
|
{ lat: 226, common_pid: 2039 } hitcount: 7
|
|
{ lat: 226, common_pid: 2036 } hitcount: 4
|
|
{ lat: 227, common_pid: 2039 } hitcount: 6
|
|
{ lat: 227, common_pid: 2036 } hitcount: 12
|
|
{ lat: 227, common_pid: 2043 } hitcount: 1
|
|
{ lat: 228, common_pid: 2039 } hitcount: 7
|
|
{ lat: 228, common_pid: 2036 } hitcount: 14
|
|
{ lat: 229, common_pid: 2039 } hitcount: 9
|
|
{ lat: 229, common_pid: 2036 } hitcount: 8
|
|
{ lat: 229, common_pid: 2038 } hitcount: 1
|
|
{ lat: 230, common_pid: 2039 } hitcount: 11
|
|
{ lat: 230, common_pid: 2036 } hitcount: 6
|
|
{ lat: 230, common_pid: 2043 } hitcount: 1
|
|
{ lat: 230, common_pid: 2042 } hitcount: 2
|
|
{ lat: 231, common_pid: 2041 } hitcount: 1
|
|
{ lat: 231, common_pid: 2036 } hitcount: 6
|
|
{ lat: 231, common_pid: 2043 } hitcount: 1
|
|
{ lat: 231, common_pid: 2039 } hitcount: 8
|
|
{ lat: 232, common_pid: 2037 } hitcount: 1
|
|
{ lat: 232, common_pid: 2039 } hitcount: 6
|
|
{ lat: 232, common_pid: 2040 } hitcount: 2
|
|
{ lat: 232, common_pid: 2036 } hitcount: 5
|
|
{ lat: 232, common_pid: 2043 } hitcount: 1
|
|
{ lat: 233, common_pid: 2036 } hitcount: 5
|
|
{ lat: 233, common_pid: 2039 } hitcount: 11
|
|
{ lat: 234, common_pid: 2039 } hitcount: 4
|
|
{ lat: 234, common_pid: 2038 } hitcount: 2
|
|
{ lat: 234, common_pid: 2043 } hitcount: 2
|
|
{ lat: 234, common_pid: 2036 } hitcount: 11
|
|
{ lat: 234, common_pid: 2040 } hitcount: 1
|
|
{ lat: 235, common_pid: 2037 } hitcount: 2
|
|
{ lat: 235, common_pid: 2036 } hitcount: 8
|
|
{ lat: 235, common_pid: 2043 } hitcount: 2
|
|
{ lat: 235, common_pid: 2039 } hitcount: 5
|
|
{ lat: 235, common_pid: 2042 } hitcount: 2
|
|
{ lat: 235, common_pid: 2040 } hitcount: 4
|
|
{ lat: 235, common_pid: 2041 } hitcount: 1
|
|
{ lat: 236, common_pid: 2036 } hitcount: 7
|
|
{ lat: 236, common_pid: 2037 } hitcount: 1
|
|
{ lat: 236, common_pid: 2041 } hitcount: 5
|
|
{ lat: 236, common_pid: 2039 } hitcount: 3
|
|
{ lat: 236, common_pid: 2043 } hitcount: 9
|
|
{ lat: 236, common_pid: 2040 } hitcount: 7
|
|
{ lat: 237, common_pid: 2037 } hitcount: 1
|
|
{ lat: 237, common_pid: 2040 } hitcount: 1
|
|
{ lat: 237, common_pid: 2036 } hitcount: 9
|
|
{ lat: 237, common_pid: 2039 } hitcount: 3
|
|
{ lat: 237, common_pid: 2043 } hitcount: 8
|
|
{ lat: 237, common_pid: 2042 } hitcount: 2
|
|
{ lat: 237, common_pid: 2041 } hitcount: 2
|
|
{ lat: 238, common_pid: 2043 } hitcount: 10
|
|
{ lat: 238, common_pid: 2040 } hitcount: 1
|
|
{ lat: 238, common_pid: 2037 } hitcount: 9
|
|
{ lat: 238, common_pid: 2038 } hitcount: 1
|
|
{ lat: 238, common_pid: 2039 } hitcount: 1
|
|
{ lat: 238, common_pid: 2042 } hitcount: 3
|
|
{ lat: 238, common_pid: 2036 } hitcount: 7
|
|
{ lat: 239, common_pid: 2041 } hitcount: 1
|
|
{ lat: 239, common_pid: 2043 } hitcount: 11
|
|
{ lat: 239, common_pid: 2037 } hitcount: 11
|
|
{ lat: 239, common_pid: 2038 } hitcount: 6
|
|
{ lat: 239, common_pid: 2036 } hitcount: 7
|
|
{ lat: 239, common_pid: 2040 } hitcount: 1
|
|
{ lat: 239, common_pid: 2042 } hitcount: 9
|
|
{ lat: 240, common_pid: 2037 } hitcount: 29
|
|
{ lat: 240, common_pid: 2043 } hitcount: 15
|
|
{ lat: 240, common_pid: 2040 } hitcount: 44
|
|
{ lat: 240, common_pid: 2039 } hitcount: 1
|
|
{ lat: 240, common_pid: 2041 } hitcount: 2
|
|
{ lat: 240, common_pid: 2038 } hitcount: 1
|
|
{ lat: 240, common_pid: 2036 } hitcount: 10
|
|
{ lat: 240, common_pid: 2042 } hitcount: 13
|
|
{ lat: 241, common_pid: 2036 } hitcount: 21
|
|
{ lat: 241, common_pid: 2041 } hitcount: 36
|
|
{ lat: 241, common_pid: 2037 } hitcount: 34
|
|
{ lat: 241, common_pid: 2042 } hitcount: 14
|
|
{ lat: 241, common_pid: 2040 } hitcount: 94
|
|
{ lat: 241, common_pid: 2039 } hitcount: 12
|
|
{ lat: 241, common_pid: 2038 } hitcount: 2
|
|
{ lat: 241, common_pid: 2043 } hitcount: 28
|
|
{ lat: 242, common_pid: 2040 } hitcount: 109
|
|
{ lat: 242, common_pid: 2041 } hitcount: 506
|
|
{ lat: 242, common_pid: 2039 } hitcount: 155
|
|
{ lat: 242, common_pid: 2042 } hitcount: 21
|
|
{ lat: 242, common_pid: 2037 } hitcount: 52
|
|
{ lat: 242, common_pid: 2043 } hitcount: 21
|
|
{ lat: 242, common_pid: 2036 } hitcount: 16
|
|
{ lat: 242, common_pid: 2038 } hitcount: 156
|
|
{ lat: 243, common_pid: 2037 } hitcount: 46
|
|
{ lat: 243, common_pid: 2039 } hitcount: 40
|
|
{ lat: 243, common_pid: 2042 } hitcount: 119
|
|
{ lat: 243, common_pid: 2041 } hitcount: 611
|
|
{ lat: 243, common_pid: 2036 } hitcount: 69
|
|
{ lat: 243, common_pid: 2038 } hitcount: 784
|
|
{ lat: 243, common_pid: 2040 } hitcount: 323
|
|
{ lat: 243, common_pid: 2043 } hitcount: 14
|
|
{ lat: 244, common_pid: 2043 } hitcount: 35
|
|
{ lat: 244, common_pid: 2042 } hitcount: 305
|
|
{ lat: 244, common_pid: 2039 } hitcount: 8
|
|
{ lat: 244, common_pid: 2040 } hitcount: 4515
|
|
{ lat: 244, common_pid: 2038 } hitcount: 371
|
|
{ lat: 244, common_pid: 2037 } hitcount: 31
|
|
{ lat: 244, common_pid: 2036 } hitcount: 114
|
|
{ lat: 244, common_pid: 2041 } hitcount: 3396
|
|
{ lat: 245, common_pid: 2036 } hitcount: 700
|
|
{ lat: 245, common_pid: 2041 } hitcount: 2772
|
|
{ lat: 245, common_pid: 2037 } hitcount: 268
|
|
{ lat: 245, common_pid: 2039 } hitcount: 472
|
|
{ lat: 245, common_pid: 2038 } hitcount: 2758
|
|
{ lat: 245, common_pid: 2042 } hitcount: 3833
|
|
{ lat: 245, common_pid: 2040 } hitcount: 3105
|
|
{ lat: 245, common_pid: 2043 } hitcount: 645
|
|
{ lat: 246, common_pid: 2038 } hitcount: 3451
|
|
{ lat: 246, common_pid: 2041 } hitcount: 142
|
|
{ lat: 246, common_pid: 2037 } hitcount: 5101
|
|
{ lat: 246, common_pid: 2040 } hitcount: 68
|
|
{ lat: 246, common_pid: 2043 } hitcount: 5099
|
|
{ lat: 246, common_pid: 2039 } hitcount: 5608
|
|
{ lat: 246, common_pid: 2042 } hitcount: 3723
|
|
{ lat: 246, common_pid: 2036 } hitcount: 4738
|
|
{ lat: 247, common_pid: 2042 } hitcount: 312
|
|
{ lat: 247, common_pid: 2043 } hitcount: 2385
|
|
{ lat: 247, common_pid: 2041 } hitcount: 452
|
|
{ lat: 247, common_pid: 2038 } hitcount: 792
|
|
{ lat: 247, common_pid: 2040 } hitcount: 78
|
|
{ lat: 247, common_pid: 2036 } hitcount: 2375
|
|
{ lat: 247, common_pid: 2039 } hitcount: 1834
|
|
{ lat: 247, common_pid: 2037 } hitcount: 2655
|
|
{ lat: 248, common_pid: 2037 } hitcount: 36
|
|
{ lat: 248, common_pid: 2042 } hitcount: 11
|
|
{ lat: 248, common_pid: 2038 } hitcount: 122
|
|
{ lat: 248, common_pid: 2036 } hitcount: 135
|
|
{ lat: 248, common_pid: 2039 } hitcount: 26
|
|
{ lat: 248, common_pid: 2041 } hitcount: 503
|
|
{ lat: 248, common_pid: 2043 } hitcount: 66
|
|
{ lat: 248, common_pid: 2040 } hitcount: 46
|
|
{ lat: 249, common_pid: 2037 } hitcount: 29
|
|
{ lat: 249, common_pid: 2038 } hitcount: 1
|
|
{ lat: 249, common_pid: 2043 } hitcount: 29
|
|
{ lat: 249, common_pid: 2039 } hitcount: 8
|
|
{ lat: 249, common_pid: 2042 } hitcount: 56
|
|
{ lat: 249, common_pid: 2040 } hitcount: 27
|
|
{ lat: 249, common_pid: 2041 } hitcount: 11
|
|
{ lat: 249, common_pid: 2036 } hitcount: 27
|
|
{ lat: 250, common_pid: 2038 } hitcount: 1
|
|
{ lat: 250, common_pid: 2036 } hitcount: 30
|
|
{ lat: 250, common_pid: 2040 } hitcount: 19
|
|
{ lat: 250, common_pid: 2043 } hitcount: 22
|
|
{ lat: 250, common_pid: 2042 } hitcount: 20
|
|
{ lat: 250, common_pid: 2041 } hitcount: 1
|
|
{ lat: 250, common_pid: 2039 } hitcount: 6
|
|
{ lat: 250, common_pid: 2037 } hitcount: 48
|
|
{ lat: 251, common_pid: 2037 } hitcount: 43
|
|
{ lat: 251, common_pid: 2039 } hitcount: 1
|
|
{ lat: 251, common_pid: 2036 } hitcount: 12
|
|
{ lat: 251, common_pid: 2042 } hitcount: 2
|
|
{ lat: 251, common_pid: 2041 } hitcount: 1
|
|
{ lat: 251, common_pid: 2043 } hitcount: 15
|
|
{ lat: 251, common_pid: 2040 } hitcount: 3
|
|
{ lat: 252, common_pid: 2040 } hitcount: 1
|
|
{ lat: 252, common_pid: 2036 } hitcount: 12
|
|
{ lat: 252, common_pid: 2037 } hitcount: 21
|
|
{ lat: 252, common_pid: 2043 } hitcount: 14
|
|
{ lat: 253, common_pid: 2037 } hitcount: 21
|
|
{ lat: 253, common_pid: 2039 } hitcount: 2
|
|
{ lat: 253, common_pid: 2036 } hitcount: 9
|
|
{ lat: 253, common_pid: 2043 } hitcount: 6
|
|
{ lat: 253, common_pid: 2040 } hitcount: 1
|
|
{ lat: 254, common_pid: 2036 } hitcount: 8
|
|
{ lat: 254, common_pid: 2043 } hitcount: 3
|
|
{ lat: 254, common_pid: 2041 } hitcount: 1
|
|
{ lat: 254, common_pid: 2042 } hitcount: 1
|
|
{ lat: 254, common_pid: 2039 } hitcount: 1
|
|
{ lat: 254, common_pid: 2037 } hitcount: 12
|
|
{ lat: 255, common_pid: 2043 } hitcount: 1
|
|
{ lat: 255, common_pid: 2037 } hitcount: 2
|
|
{ lat: 255, common_pid: 2036 } hitcount: 2
|
|
{ lat: 255, common_pid: 2039 } hitcount: 8
|
|
{ lat: 256, common_pid: 2043 } hitcount: 1
|
|
{ lat: 256, common_pid: 2036 } hitcount: 4
|
|
{ lat: 256, common_pid: 2039 } hitcount: 6
|
|
{ lat: 257, common_pid: 2039 } hitcount: 5
|
|
{ lat: 257, common_pid: 2036 } hitcount: 4
|
|
{ lat: 258, common_pid: 2039 } hitcount: 5
|
|
{ lat: 258, common_pid: 2036 } hitcount: 2
|
|
{ lat: 259, common_pid: 2036 } hitcount: 7
|
|
{ lat: 259, common_pid: 2039 } hitcount: 7
|
|
{ lat: 260, common_pid: 2036 } hitcount: 8
|
|
{ lat: 260, common_pid: 2039 } hitcount: 6
|
|
{ lat: 261, common_pid: 2036 } hitcount: 5
|
|
{ lat: 261, common_pid: 2039 } hitcount: 7
|
|
{ lat: 262, common_pid: 2039 } hitcount: 5
|
|
{ lat: 262, common_pid: 2036 } hitcount: 5
|
|
{ lat: 263, common_pid: 2039 } hitcount: 7
|
|
{ lat: 263, common_pid: 2036 } hitcount: 7
|
|
{ lat: 264, common_pid: 2039 } hitcount: 9
|
|
{ lat: 264, common_pid: 2036 } hitcount: 9
|
|
{ lat: 265, common_pid: 2036 } hitcount: 5
|
|
{ lat: 265, common_pid: 2039 } hitcount: 1
|
|
{ lat: 266, common_pid: 2036 } hitcount: 1
|
|
{ lat: 266, common_pid: 2039 } hitcount: 3
|
|
{ lat: 267, common_pid: 2036 } hitcount: 1
|
|
{ lat: 267, common_pid: 2039 } hitcount: 3
|
|
{ lat: 268, common_pid: 2036 } hitcount: 1
|
|
{ lat: 268, common_pid: 2039 } hitcount: 6
|
|
{ lat: 269, common_pid: 2036 } hitcount: 1
|
|
{ lat: 269, common_pid: 2043 } hitcount: 1
|
|
{ lat: 269, common_pid: 2039 } hitcount: 2
|
|
{ lat: 270, common_pid: 2040 } hitcount: 1
|
|
{ lat: 270, common_pid: 2039 } hitcount: 6
|
|
{ lat: 271, common_pid: 2041 } hitcount: 1
|
|
{ lat: 271, common_pid: 2039 } hitcount: 5
|
|
{ lat: 272, common_pid: 2039 } hitcount: 10
|
|
{ lat: 273, common_pid: 2039 } hitcount: 8
|
|
{ lat: 274, common_pid: 2039 } hitcount: 2
|
|
{ lat: 275, common_pid: 2039 } hitcount: 1
|
|
{ lat: 276, common_pid: 2039 } hitcount: 2
|
|
{ lat: 276, common_pid: 2037 } hitcount: 1
|
|
{ lat: 276, common_pid: 2038 } hitcount: 1
|
|
{ lat: 277, common_pid: 2039 } hitcount: 1
|
|
{ lat: 277, common_pid: 2042 } hitcount: 1
|
|
{ lat: 278, common_pid: 2039 } hitcount: 1
|
|
{ lat: 279, common_pid: 2039 } hitcount: 4
|
|
{ lat: 279, common_pid: 2043 } hitcount: 1
|
|
{ lat: 280, common_pid: 2039 } hitcount: 3
|
|
{ lat: 283, common_pid: 2036 } hitcount: 2
|
|
{ lat: 284, common_pid: 2039 } hitcount: 1
|
|
{ lat: 284, common_pid: 2043 } hitcount: 1
|
|
{ lat: 288, common_pid: 2039 } hitcount: 1
|
|
{ lat: 289, common_pid: 2039 } hitcount: 1
|
|
{ lat: 300, common_pid: 2039 } hitcount: 1
|
|
{ lat: 384, common_pid: 2039 } hitcount: 1
|
|
|
|
Totals:
|
|
Hits: 67625
|
|
Entries: 278
|
|
Dropped: 0
|
|
|
|
Note, the writes are around the sleep, so ideally they will all be of 250
|
|
microseconds. If you are wondering how there are several that are under
|
|
250 microseconds, that is because the way cyclictest works, is if one
|
|
iteration comes in late, the next one will set the timer to wake up less that
|
|
250. That is, if an iteration came in 50 microseconds late, the next wake up
|
|
will be at 200 microseconds.
|
|
|
|
But this could easily be done in userspace. To make this even more
|
|
interesting, we can mix the histogram between events that happened in the
|
|
kernel with trace_marker::
|
|
|
|
# cd /sys/kernel/tracing
|
|
# echo 'latency u64 lat' > synthetic_events
|
|
# echo 'hist:keys=pid:ts0=common_timestamp.usecs' > events/sched/sched_waking/trigger
|
|
# echo 'hist:keys=common_pid:lat=common_timestamp.usecs-$ts0:onmatch(sched.sched_waking).latency($lat) if buf == "end"' > events/ftrace/print/trigger
|
|
# echo 'hist:keys=lat,common_pid:sort=lat' > events/synthetic/latency/trigger
|
|
|
|
The difference this time is that instead of using the trace_marker to start
|
|
the latency, the sched_waking event is used, matching the common_pid for the
|
|
trace_marker write with the pid that is being woken by sched_waking.
|
|
|
|
After running cyclictest again with the same parameters, we now have::
|
|
|
|
# cat events/synthetic/latency/hist
|
|
# event histogram
|
|
#
|
|
# trigger info: hist:keys=lat,common_pid:vals=hitcount:sort=lat:size=2048 [active]
|
|
#
|
|
|
|
{ lat: 7, common_pid: 2302 } hitcount: 640
|
|
{ lat: 7, common_pid: 2299 } hitcount: 42
|
|
{ lat: 7, common_pid: 2303 } hitcount: 18
|
|
{ lat: 7, common_pid: 2305 } hitcount: 166
|
|
{ lat: 7, common_pid: 2306 } hitcount: 1
|
|
{ lat: 7, common_pid: 2301 } hitcount: 91
|
|
{ lat: 7, common_pid: 2300 } hitcount: 17
|
|
{ lat: 8, common_pid: 2303 } hitcount: 8296
|
|
{ lat: 8, common_pid: 2304 } hitcount: 6864
|
|
{ lat: 8, common_pid: 2305 } hitcount: 9464
|
|
{ lat: 8, common_pid: 2301 } hitcount: 9213
|
|
{ lat: 8, common_pid: 2306 } hitcount: 6246
|
|
{ lat: 8, common_pid: 2302 } hitcount: 8797
|
|
{ lat: 8, common_pid: 2299 } hitcount: 8771
|
|
{ lat: 8, common_pid: 2300 } hitcount: 8119
|
|
{ lat: 9, common_pid: 2305 } hitcount: 1519
|
|
{ lat: 9, common_pid: 2299 } hitcount: 2346
|
|
{ lat: 9, common_pid: 2303 } hitcount: 2841
|
|
{ lat: 9, common_pid: 2301 } hitcount: 1846
|
|
{ lat: 9, common_pid: 2304 } hitcount: 3861
|
|
{ lat: 9, common_pid: 2302 } hitcount: 1210
|
|
{ lat: 9, common_pid: 2300 } hitcount: 2762
|
|
{ lat: 9, common_pid: 2306 } hitcount: 4247
|
|
{ lat: 10, common_pid: 2299 } hitcount: 16
|
|
{ lat: 10, common_pid: 2306 } hitcount: 333
|
|
{ lat: 10, common_pid: 2303 } hitcount: 16
|
|
{ lat: 10, common_pid: 2304 } hitcount: 168
|
|
{ lat: 10, common_pid: 2302 } hitcount: 240
|
|
{ lat: 10, common_pid: 2301 } hitcount: 28
|
|
{ lat: 10, common_pid: 2300 } hitcount: 95
|
|
{ lat: 10, common_pid: 2305 } hitcount: 18
|
|
{ lat: 11, common_pid: 2303 } hitcount: 5
|
|
{ lat: 11, common_pid: 2305 } hitcount: 8
|
|
{ lat: 11, common_pid: 2306 } hitcount: 221
|
|
{ lat: 11, common_pid: 2302 } hitcount: 76
|
|
{ lat: 11, common_pid: 2304 } hitcount: 26
|
|
{ lat: 11, common_pid: 2300 } hitcount: 125
|
|
{ lat: 11, common_pid: 2299 } hitcount: 2
|
|
{ lat: 12, common_pid: 2305 } hitcount: 3
|
|
{ lat: 12, common_pid: 2300 } hitcount: 6
|
|
{ lat: 12, common_pid: 2306 } hitcount: 90
|
|
{ lat: 12, common_pid: 2302 } hitcount: 4
|
|
{ lat: 12, common_pid: 2303 } hitcount: 1
|
|
{ lat: 12, common_pid: 2304 } hitcount: 122
|
|
{ lat: 13, common_pid: 2300 } hitcount: 12
|
|
{ lat: 13, common_pid: 2301 } hitcount: 1
|
|
{ lat: 13, common_pid: 2306 } hitcount: 32
|
|
{ lat: 13, common_pid: 2302 } hitcount: 5
|
|
{ lat: 13, common_pid: 2305 } hitcount: 1
|
|
{ lat: 13, common_pid: 2303 } hitcount: 1
|
|
{ lat: 13, common_pid: 2304 } hitcount: 61
|
|
{ lat: 14, common_pid: 2303 } hitcount: 4
|
|
{ lat: 14, common_pid: 2306 } hitcount: 5
|
|
{ lat: 14, common_pid: 2305 } hitcount: 4
|
|
{ lat: 14, common_pid: 2304 } hitcount: 62
|
|
{ lat: 14, common_pid: 2302 } hitcount: 19
|
|
{ lat: 14, common_pid: 2300 } hitcount: 33
|
|
{ lat: 14, common_pid: 2299 } hitcount: 1
|
|
{ lat: 14, common_pid: 2301 } hitcount: 4
|
|
{ lat: 15, common_pid: 2305 } hitcount: 1
|
|
{ lat: 15, common_pid: 2302 } hitcount: 25
|
|
{ lat: 15, common_pid: 2300 } hitcount: 11
|
|
{ lat: 15, common_pid: 2299 } hitcount: 5
|
|
{ lat: 15, common_pid: 2301 } hitcount: 1
|
|
{ lat: 15, common_pid: 2304 } hitcount: 8
|
|
{ lat: 15, common_pid: 2303 } hitcount: 1
|
|
{ lat: 15, common_pid: 2306 } hitcount: 6
|
|
{ lat: 16, common_pid: 2302 } hitcount: 31
|
|
{ lat: 16, common_pid: 2306 } hitcount: 3
|
|
{ lat: 16, common_pid: 2300 } hitcount: 5
|
|
{ lat: 17, common_pid: 2302 } hitcount: 6
|
|
{ lat: 17, common_pid: 2303 } hitcount: 1
|
|
{ lat: 18, common_pid: 2304 } hitcount: 1
|
|
{ lat: 18, common_pid: 2302 } hitcount: 8
|
|
{ lat: 18, common_pid: 2299 } hitcount: 1
|
|
{ lat: 18, common_pid: 2301 } hitcount: 1
|
|
{ lat: 19, common_pid: 2303 } hitcount: 4
|
|
{ lat: 19, common_pid: 2304 } hitcount: 5
|
|
{ lat: 19, common_pid: 2302 } hitcount: 4
|
|
{ lat: 19, common_pid: 2299 } hitcount: 3
|
|
{ lat: 19, common_pid: 2306 } hitcount: 1
|
|
{ lat: 19, common_pid: 2300 } hitcount: 4
|
|
{ lat: 19, common_pid: 2305 } hitcount: 5
|
|
{ lat: 20, common_pid: 2299 } hitcount: 2
|
|
{ lat: 20, common_pid: 2302 } hitcount: 3
|
|
{ lat: 20, common_pid: 2305 } hitcount: 1
|
|
{ lat: 20, common_pid: 2300 } hitcount: 2
|
|
{ lat: 20, common_pid: 2301 } hitcount: 2
|
|
{ lat: 20, common_pid: 2303 } hitcount: 3
|
|
{ lat: 21, common_pid: 2305 } hitcount: 1
|
|
{ lat: 21, common_pid: 2299 } hitcount: 5
|
|
{ lat: 21, common_pid: 2303 } hitcount: 4
|
|
{ lat: 21, common_pid: 2302 } hitcount: 7
|
|
{ lat: 21, common_pid: 2300 } hitcount: 1
|
|
{ lat: 21, common_pid: 2301 } hitcount: 5
|
|
{ lat: 21, common_pid: 2304 } hitcount: 2
|
|
{ lat: 22, common_pid: 2302 } hitcount: 5
|
|
{ lat: 22, common_pid: 2303 } hitcount: 1
|
|
{ lat: 22, common_pid: 2306 } hitcount: 3
|
|
{ lat: 22, common_pid: 2301 } hitcount: 2
|
|
{ lat: 22, common_pid: 2300 } hitcount: 1
|
|
{ lat: 22, common_pid: 2299 } hitcount: 1
|
|
{ lat: 22, common_pid: 2305 } hitcount: 1
|
|
{ lat: 22, common_pid: 2304 } hitcount: 1
|
|
{ lat: 23, common_pid: 2299 } hitcount: 1
|
|
{ lat: 23, common_pid: 2306 } hitcount: 2
|
|
{ lat: 23, common_pid: 2302 } hitcount: 6
|
|
{ lat: 24, common_pid: 2302 } hitcount: 3
|
|
{ lat: 24, common_pid: 2300 } hitcount: 1
|
|
{ lat: 24, common_pid: 2306 } hitcount: 2
|
|
{ lat: 24, common_pid: 2305 } hitcount: 1
|
|
{ lat: 24, common_pid: 2299 } hitcount: 1
|
|
{ lat: 25, common_pid: 2300 } hitcount: 1
|
|
{ lat: 25, common_pid: 2302 } hitcount: 4
|
|
{ lat: 26, common_pid: 2302 } hitcount: 2
|
|
{ lat: 27, common_pid: 2305 } hitcount: 1
|
|
{ lat: 27, common_pid: 2300 } hitcount: 1
|
|
{ lat: 27, common_pid: 2302 } hitcount: 3
|
|
{ lat: 28, common_pid: 2306 } hitcount: 1
|
|
{ lat: 28, common_pid: 2302 } hitcount: 4
|
|
{ lat: 29, common_pid: 2302 } hitcount: 1
|
|
{ lat: 29, common_pid: 2300 } hitcount: 2
|
|
{ lat: 29, common_pid: 2306 } hitcount: 1
|
|
{ lat: 29, common_pid: 2304 } hitcount: 1
|
|
{ lat: 30, common_pid: 2302 } hitcount: 4
|
|
{ lat: 31, common_pid: 2302 } hitcount: 6
|
|
{ lat: 32, common_pid: 2302 } hitcount: 1
|
|
{ lat: 33, common_pid: 2299 } hitcount: 1
|
|
{ lat: 33, common_pid: 2302 } hitcount: 3
|
|
{ lat: 34, common_pid: 2302 } hitcount: 2
|
|
{ lat: 35, common_pid: 2302 } hitcount: 1
|
|
{ lat: 35, common_pid: 2304 } hitcount: 1
|
|
{ lat: 36, common_pid: 2302 } hitcount: 4
|
|
{ lat: 37, common_pid: 2302 } hitcount: 6
|
|
{ lat: 38, common_pid: 2302 } hitcount: 2
|
|
{ lat: 39, common_pid: 2302 } hitcount: 2
|
|
{ lat: 39, common_pid: 2304 } hitcount: 1
|
|
{ lat: 40, common_pid: 2304 } hitcount: 2
|
|
{ lat: 40, common_pid: 2302 } hitcount: 5
|
|
{ lat: 41, common_pid: 2304 } hitcount: 1
|
|
{ lat: 41, common_pid: 2302 } hitcount: 8
|
|
{ lat: 42, common_pid: 2302 } hitcount: 6
|
|
{ lat: 42, common_pid: 2304 } hitcount: 1
|
|
{ lat: 43, common_pid: 2302 } hitcount: 3
|
|
{ lat: 43, common_pid: 2304 } hitcount: 4
|
|
{ lat: 44, common_pid: 2302 } hitcount: 6
|
|
{ lat: 45, common_pid: 2302 } hitcount: 5
|
|
{ lat: 46, common_pid: 2302 } hitcount: 5
|
|
{ lat: 47, common_pid: 2302 } hitcount: 7
|
|
{ lat: 48, common_pid: 2301 } hitcount: 1
|
|
{ lat: 48, common_pid: 2302 } hitcount: 9
|
|
{ lat: 49, common_pid: 2302 } hitcount: 3
|
|
{ lat: 50, common_pid: 2302 } hitcount: 1
|
|
{ lat: 50, common_pid: 2301 } hitcount: 1
|
|
{ lat: 51, common_pid: 2302 } hitcount: 2
|
|
{ lat: 51, common_pid: 2301 } hitcount: 1
|
|
{ lat: 61, common_pid: 2302 } hitcount: 1
|
|
{ lat: 110, common_pid: 2302 } hitcount: 1
|
|
|
|
Totals:
|
|
Hits: 89565
|
|
Entries: 158
|
|
Dropped: 0
|
|
|
|
This doesn't tell us any information about how late cyclictest may have
|
|
woken up, but it does show us a nice histogram of how long it took from
|
|
the time that cyclictest was woken to the time it made it into user space.
|