PERF-SCHED(1) | perf Manual | PERF-SCHED(1) |
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.
OPTIONS FOR PERF SCHED REPLAY
-r, --repeat <n>
repeat the workload n times (0: infinite). Default is
10.
SEE ALSO
2024-09-03 | perf |