# perf-sched

## NAME



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


## SYNOPSIS



           _perf sched_ {record|latency|map|replay|script|timehist}
    


## 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
                                        [tid/pid]                (msec)     (msec)     (msec)
                 -------------- ------  --------------------  ---------  ---------  ---------
                   79371.874569 [0011]  gcc[31949]                0.014      0.000      1.148
                   79371.874591 [0010]  gcc[31951]                0.000      0.000      0.024
                   79371.874603 [0010]  migration/10[59]          3.350      0.004      0.011
                   79371.874604 [0011]  <idle>                    1.148      0.000      0.035
                   79371.874723 [0005]  <idle>                    0.016      0.000      1.383
                   79371.874746 [0005]  gcc[31949]                0.153      0.078      0.022
               ...
    
               Times are in msec.usec.
    


## OPTIONS



           -i, --input=<file>
               Input file name. (default: perf.data unless stdin is a fifo)
    
           -v, --verbose
               Be more verbose. (show symbol address, etc)
    
           -D, --dump-raw-trace=
               Display verbose dump of the sched data.
    
           -f, --force
               Don’t complain, do it.
    


## OPTIONS FOR PERF SCHED LATENCY



           -C, --CPU <n>
               CPU to profile on.
    
           -p, --pids
               latency stats per pid instead of per command name.
    
           -s, --sort <key[,key2...]>
               sort by key(s): runtime, switch, avg, max by default it’s
               sorted by "avg ,max ,switch ,runtime".
    


## OPTIONS FOR PERF SCHED MAP



           --compact
               Show only CPUs with activity. Helps visualizing on high core
               count systems.
    
           --cpus
               Show just entries with activities for the given CPUs.
    
           --color-cpus
               Highlight the given cpus.
    
           --color-pids
               Highlight the given pids.
    
           --task-name <task>
               Map output only for the given task name(s). Separate the task
               names with a comma (without whitespace). The sched-out time is
               printed and is represented by _*-_ for the given task name(s).
               (_-_ indicates other tasks while _._  is idle).
    
           --fuzzy-name
               Given task name(s) can be partially matched (fuzzy matching).
    


## OPTIONS FOR PERF SCHED TIMEHIST



           -k, --vmlinux=<file>
               vmlinux pathname
    
           --kallsyms=<file>
               kallsyms pathname
    
           -g, --call-graph
               Display call chains if present (default on).
    
           --max-stack
               Maximum number of functions to display in backtrace, default
               5.
    
           -C=, --cpu=
               Only show events for the given CPU(s) (comma separated list).
    
           -p=, --pid=
               Only show events for given process ID (comma separated list).
    
           -t=, --tid=
               Only show events for given thread ID (comma separated list).
    
           -s, --summary
               Show only a summary of scheduling by thread with min, max, and
               average run times (in sec) and relative stddev.
    
           -S, --with-summary
               Show all scheduling events followed by a summary by thread
               with min, max, and average run times (in sec) and relative
               stddev.
    
           --symfs=<directory>
               Look for files with symbols relative to this directory.
    
           -V, --cpu-visual
               Show visual aid for sched switches by CPU: _i_ marks idle time,
               _s_ are scheduler events.
    
           -w, --wakeups
               Show wakeup events.
    
           -M, --migrations
               Show migration events.
    
           -n, --next
               Show next task.
    
           -I, --idle-hist
               Show idle-related events only.
    
           --time
               Only analyze samples within given time window: <start>,<stop>.
               Times have the format seconds.microseconds. If start is not
               given (i.e., time string is _,x.y_) then analysis starts at the
               beginning of the file. If stop time is not given (i.e, time
               string is _x.y,_) then analysis goes to end of file.
    
           --state
               Show task state when it switched out.
    
           --show-prio
               Show task priority.
    
           --prio
               Only show events for given task priority(ies). Multiple
               priorities can be provided as a comma-separated list with no
               spaces: 0,120. Ranges of priorities are specified with -:
               120-129. A combination of both can also be provided:
               0,120-129.
    
           -P, --pre-migrations
               Show pre-migration wait time. pre-migration wait time is the
               time spent by a task waiting on a runqueue but not getting the
               chance to run there and is migrated to a different runqueue
               where it is finally run. This time between sched_wakeup and
               migrate_task is the pre-migration wait time.
    


## OPTIONS FOR PERF SCHED REPLAY



           -r, --repeat <n>
               repeat the workload n times (0: infinite). Default is 10.
    


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