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55c40e5052
Some common tools for collecting statistics on CPU usage, such as top,
obtain statistics from timer interrupt sampling, and then periodically
read statistics from /proc/stat.
This method has some deviations:
1. In the tick interrupt, the time between the last tick and the current
tick is counted in the current task. However, the task may be running
only part of the time.
2. For each task, the top tool periodically reads the /proc/{PID}/status
information. For tasks with a short life cycle, it may be missed.
In conclusion, the top tool cannot accurately collect statistics on the
CPU usage and running time of tasks.
The statistical method based on sched_switch tracepoint can accurately
calculate the CPU usage of all tasks. This method is applicable to
scenarios where performance comparison data is of high precision.
Example usage:
# perf kwork
Usage: perf kwork [<options>] {record|report|latency|timehist|top}
-D, --dump-raw-trace dump raw trace in ASCII
-f, --force don't complain, do it
-k, --kwork <kwork> list of kwork to profile (irq, softirq, workqueue, sched, etc)
-v, --verbose be more verbose (show symbol address, etc)
# perf kwork -k sched record -- perf bench sched messaging -g 1 -l 10000
# Running 'sched/messaging' benchmark:
# 20 sender and receiver processes per group
# 1 groups == 40 processes run
Total time: 14.074 [sec]
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 15.886 MB perf.data (129472 samples) ]
# perf kwork top
Total : 115708.178 ms, 8 cpus
%Cpu(s): 9.78% id
%Cpu0 [||||||||||||||||||||||||||| 90.55%]
%Cpu1 [||||||||||||||||||||||||||| 90.51%]
%Cpu2 [|||||||||||||||||||||||||| 88.57%]
%Cpu3 [||||||||||||||||||||||||||| 91.18%]
%Cpu4 [||||||||||||||||||||||||||| 91.09%]
%Cpu5 [||||||||||||||||||||||||||| 90.88%]
%Cpu6 [|||||||||||||||||||||||||| 88.64%]
%Cpu7 [||||||||||||||||||||||||||| 90.28%]
PID %CPU RUNTIME COMMMAND
----------------------------------------------------
4113 22.23 3221.547 ms sched-messaging
4105 21.61 3131.495 ms sched-messaging
4119 21.53 3120.937 ms sched-messaging
4103 21.39 3101.614 ms sched-messaging
4106 21.37 3095.209 ms sched-messaging
4104 21.25 3077.269 ms sched-messaging
4115 21.21 3073.188 ms sched-messaging
4109 21.18 3069.022 ms sched-messaging
4111 20.78 3010.033 ms sched-messaging
4114 20.74 3007.073 ms sched-messaging
4108 20.73 3002.137 ms sched-messaging
4107 20.47 2967.292 ms sched-messaging
4117 20.39 2955.335 ms sched-messaging
4112 20.34 2947.080 ms sched-messaging
4118 20.32 2942.519 ms sched-messaging
4121 20.23 2929.865 ms sched-messaging
4110 20.22 2930.078 ms sched-messaging
4122 20.15 2919.542 ms sched-messaging
4120 19.77 2866.032 ms sched-messaging
4116 19.72 2857.660 ms sched-messaging
4127 16.19 2346.334 ms sched-messaging
4142 15.86 2297.600 ms sched-messaging
4141 15.62 2262.646 ms sched-messaging
4136 15.41 2231.408 ms sched-messaging
4130 15.38 2227.008 ms sched-messaging
4129 15.31 2217.692 ms sched-messaging
4126 15.21 2201.711 ms sched-messaging
4139 15.19 2200.722 ms sched-messaging
4137 15.10 2188.633 ms sched-messaging
4134 15.06 2182.082 ms sched-messaging
4132 15.02 2177.530 ms sched-messaging
4131 14.73 2131.973 ms sched-messaging
4125 14.68 2125.439 ms sched-messaging
4128 14.66 2122.255 ms sched-messaging
4123 14.65 2122.113 ms sched-messaging
4135 14.56 2107.144 ms sched-messaging
4133 14.51 2103.549 ms sched-messaging
4124 14.27 2066.671 ms sched-messaging
4140 14.17 2052.251 ms sched-messaging
4138 13.81 2000.361 ms sched-messaging
0 11.42 1652.009 ms swapper/2
0 11.35 1641.694 ms swapper/6
0 9.71 1405.108 ms swapper/7
0 9.48 1372.338 ms swapper/1
0 9.44 1366.013 ms swapper/0
0 9.11 1318.382 ms swapper/5
0 8.90 1287.582 ms swapper/4
0 8.81 1274.356 ms swapper/3
4100 2.61 379.328 ms perf
4101 1.16 169.487 ms perf-exec
151 0.65 94.741 ms systemd-resolve
249 0.36 53.030 ms sd-resolve
153 0.14 21.405 ms systemd-timesyn
1 0.10 16.200 ms systemd
16 0.09 15.785 ms rcu_preempt
4102 0.06 9.727 ms perf
4095 0.03 5.464 ms kworker/7:1
98 0.02 3.231 ms jbd2/sda-8
353 0.02 4.115 ms sshd
75 0.02 3.889 ms kworker/2:1
73 0.01 1.552 ms kworker/5:1
64 0.01 1.591 ms kworker/4:1
74 0.01 1.952 ms kworker/3:1
61 0.01 2.608 ms kcompactd0
397 0.01 1.602 ms kworker/1:1
69 0.01 1.817 ms kworker/1:1H
10 0.01 2.553 ms kworker/u16:0
2909 0.01 2.684 ms kworker/0:2
1211 0.00 0.426 ms kworker/7:0
97 0.00 0.153 ms kworker/7:1H
51 0.00 0.100 ms ksoftirqd/7
120 0.00 0.856 ms systemd-journal
76 0.00 1.414 ms kworker/6:1
46 0.00 0.246 ms ksoftirqd/6
45 0.00 0.164 ms migration/6
41 0.00 0.098 ms ksoftirqd/5
40 0.00 0.207 ms migration/5
86 0.00 1.339 ms kworker/4:1H
36 0.00 0.252 ms ksoftirqd/4
35 0.00 0.090 ms migration/4
31 0.00 0.156 ms ksoftirqd/3
30 0.00 0.073 ms migration/3
26 0.00 0.180 ms ksoftirqd/2
25 0.00 0.085 ms migration/2
21 0.00 0.106 ms ksoftirqd/1
20 0.00 0.118 ms migration/1
302 0.00 1.440 ms systemd-logind
17 0.00 0.132 ms migration/0
15 0.00 0.255 ms ksoftirqd/0
Reviewed-by: Ian Rogers <irogers@google.com>
Signed-off-by: Yang Jihong <yangjihong1@huawei.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ravi Bangoria <ravi.bangoria@amd.com>
Cc: Sandipan Das <sandipan.das@amd.com>
Link: https://lore.kernel.org/r/20230812084917.169338-10-yangjihong1@huawei.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
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Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.