tools/perf/Documentation/perf-sched.txt

Source file repositories/reference/linux-study-clean/tools/perf/Documentation/perf-sched.txt

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Linux kernel
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tools/perf/Documentation/perf-sched.txt
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.txt
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Support Tooling And Documentation
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tools
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Support Tooling And Documentation: documentation
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atlas-only

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Repository support layer: documentation, build tooling, samples, user-space helper tools, generated initramfs support, licenses, and validation utilities.

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perf-sched(1)
=============

NAME
----
perf-sched - Tool to trace/measure scheduler properties (latencies)

SYNOPSIS
--------
[verse]
'perf sched' {record|latency|map|replay|script|timehist|stats}

DESCRIPTION
-----------
There are several variants of 'perf sched':

  'perf sched record <command>' to record the scheduling events
  of an arbitrary workload.

  'perf sched latency' to report the per task scheduling latencies
  and other scheduling properties of the workload.

   Example usage:
       perf sched record -- sleep 1
       perf sched latency

  -------------------------------------------------------------------------------------------------------------------------------------------
  Task                  |   Runtime ms  |  Count   | Avg delay ms    | Max delay ms    | Max delay start           | Max delay end          |
  -------------------------------------------------------------------------------------------------------------------------------------------
  perf:(2)              |      2.804 ms |       66 | avg:   0.524 ms | max:   1.069 ms | max start: 254752.314960 s | max end: 254752.316029 s
  NetworkManager:1343   |      0.372 ms |       13 | avg:   0.008 ms | max:   0.013 ms | max start: 254751.551153 s | max end: 254751.551166 s
  kworker/1:2-xfs:4649  |      0.012 ms |        1 | avg:   0.008 ms | max:   0.008 ms | max start: 254751.519807 s | max end: 254751.519815 s
  kworker/3:1-xfs:388   |      0.011 ms |        1 | avg:   0.006 ms | max:   0.006 ms | max start: 254751.519809 s | max end: 254751.519815 s
  sleep:147736          |      0.938 ms |        3 | avg:   0.006 ms | max:   0.007 ms | max start: 254751.313817 s | max end: 254751.313824 s

  It shows Runtime(time that a task spent actually running on the CPU),
  Count(number of times a delay was calculated) and delay(time that a
  task was ready to run but was kept waiting).

  Tasks with the same command name are merged and the merge count is
  given within (), However if -p option is used, pid is mentioned.

  'perf sched script' to see a detailed trace of the workload that
   was recorded (aliased to 'perf script' for now).

  'perf sched replay' to simulate the workload that was recorded
  via perf sched record. (this is done by starting up mockup threads
  that mimic the workload based on the events in the trace. These
  threads can then replay the timings (CPU runtime and sleep patterns)
  of the workload as it occurred when it was recorded - and can repeat
  it a number of times, measuring its performance.)

  'perf sched map' to print a textual context-switching outline of
  workload captured via perf sched record.  Columns stand for
  individual CPUs, and the two-letter shortcuts stand for tasks that
  are running on a CPU. A '*' denotes the CPU that had the event, and
  a dot signals an idle CPU.

  'perf sched timehist' provides an analysis of scheduling events.
    
    Example usage:
        perf sched record -- sleep 1
        perf sched timehist
    
   By default it shows the individual schedule events, including the wait
   time (time between sched-out and next sched-in events for the task), the
   task scheduling delay (time between runnable and actually running) and
   run time for the task:
    
                time    cpu  task name             wait time  sch delay   run time

Annotation

Implementation Notes