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Date: Tue, 5 Sep 2023 09:01:05 +0800
From: Yang Jihong <yangjihong1@...wei.com>
To: Ian Rogers <irogers@...gle.com>
CC: <peterz@...radead.org>, <mingo@...hat.com>, <acme@...nel.org>,
<mark.rutland@....com>, <alexander.shishkin@...ux.intel.com>,
<jolsa@...nel.org>, <namhyung@...nel.org>,
<adrian.hunter@...el.com>, <kan.liang@...ux.intel.com>,
<sandipan.das@....com>, <ravi.bangoria@....com>,
<linux-kernel@...r.kernel.org>, <linux-perf-users@...r.kernel.org>
Subject: Re: [RFC v1 00/16] perf kwork: Implement perf kwork top
Hello,
On 2023/9/4 22:54, Ian Rogers wrote:
> On Mon, Sep 4, 2023 at 4:59 AM Yang Jihong <yangjihong1@...wei.com> wrote:
>>
>> Hello,
>>
>> On 2023/9/4 13:13, Ian Rogers wrote:
>>> On Sat, Aug 12, 2023 at 1:52 AM Yang Jihong <yangjihong1@...wei.com> wrote:
>>>>
>>>> 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.
>>>>
>>>> In addition to parsing the perf.data file, the provides BPF-based CPU usage
>>>> statistics to reduce the load of the perf process.
>>>>
>>>> Example usage:
>>>>
>>>> # perf kwork top -h
>>>>
>>>> Usage: perf kwork top [<options>]
>>>>
>>>> -C, --cpu <cpu> list of cpus to profile
>>>> -i, --input <file> input file name
>>>> -n, --name <name> event name to profile
>>>> -s, --sort <key[,key2...]>
>>>> sort by key(s): rate, runtime, tid
>>>> --time <str> Time span for analysis (start,stop)
>>>>
>>>> # ./perf kwork -k sched,irq,softirq 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: 1.854 [sec]
>>>> [ perf record: Woken up 13 times to write data ]
>>>> [ perf record: Captured and wrote 27.436 MB perf.data (235986 samples) ]
>>>> #
>>>> # perf kwork top
>>>>
>>>> Total : 22419.068 ms, 12 cpus
>>>> %Cpu(s): 17.99% id, 0.00% hi, 0.09% si
>>>> %Cpu0 [|||||||||||||||||||||||| 82.56%]
>>>> %Cpu1 [|||||||||||||||||||||||| 81.73%]
>>>> %Cpu2 [|||||||||||||||||||||||| 83.00%]
>>>> %Cpu3 [|||||||||||||||||||||||| 81.01%]
>>>> %Cpu4 [|||||||||||||||||||||||| 81.66%]
>>>> %Cpu5 [|||||||||||||||||||||||| 82.10%]
>>>> %Cpu6 [|||||||||||||||||||||||| 81.65%]
>>>> %Cpu7 [|||||||||||||||||||||||| 82.00%]
>>>> %Cpu8 [|||||||||||||||||||||||| 82.54%]
>>>> %Cpu9 [|||||||||||||||||||||||| 81.02%]
>>>> %Cpu10 [|||||||||||||||||||||||| 81.78%]
>>>> %Cpu11 [|||||||||||||||||||||||| 81.87%]
>>>>
>>>> PID %CPU RUNTIME COMMMAND
>>>> ----------------------------------------------------
>>>> 2913025 27.62 516.976 ms sched-messaging
>>>> 2913017 27.56 516.273 ms sched-messaging
>>>> 2913018 27.56 516.152 ms sched-messaging
>>>> 2913008 27.54 515.447 ms sched-messaging
>>>> 2913010 27.50 514.890 ms sched-messaging
>>>> 2913007 27.48 514.411 ms sched-messaging
>>>> 2913015 27.36 512.563 ms sched-messaging
>>>> 2913026 27.35 512.198 ms sched-messaging
>>>> 2913011 27.32 511.632 ms sched-messaging
>>>> 2913014 27.32 511.381 ms sched-messaging
>>>> 2913012 27.30 511.138 ms sched-messaging
>>>> 2913013 27.30 511.109 ms sched-messaging
>>>> 2913009 27.30 510.997 ms sched-messaging
>>>> 2913019 27.25 510.488 ms sched-messaging
>>>> 2913021 27.23 509.661 ms sched-messaging
>>>> 2913023 27.21 509.400 ms sched-messaging
>>>> 2913020 27.20 509.677 ms sched-messaging
>>>> 2913022 27.19 509.061 ms sched-messaging
>>>> 2913016 27.18 509.231 ms sched-messaging
>>>> 2913024 27.18 509.108 ms sched-messaging
>>>> 2912999 21.79 407.929 ms sched-messaging
>>>> 2913000 21.78 408.045 ms sched-messaging
>>>> 2912998 21.75 407.579 ms sched-messaging
>>>> 2912993 21.69 406.166 ms sched-messaging
>>>> 2912991 21.59 404.378 ms sched-messaging
>>>> 2912992 21.57 403.845 ms sched-messaging
>>>> 2913005 21.56 403.715 ms sched-messaging
>>>> 2913001 21.55 403.803 ms sched-messaging
>>>> 2912990 21.54 403.601 ms sched-messaging
>>>> 2912994 21.52 403.087 ms sched-messaging
>>>> 2912995 21.49 402.421 ms sched-messaging
>>>> 2912996 21.48 402.666 ms sched-messaging
>>>> 2912989 21.46 402.303 ms sched-messaging
>>>> 2913003 21.46 402.034 ms sched-messaging
>>>> 2912988 21.44 401.820 ms sched-messaging
>>>> 2913004 21.37 400.242 ms sched-messaging
>>>> 2912987 21.28 398.512 ms sched-messaging
>>>> 2913002 21.27 398.759 ms sched-messaging
>>>> 2912997 21.27 398.518 ms sched-messaging
>>>> 2913006 21.23 397.888 ms sched-messaging
>>>> 0 18.89 353.061 ms swapper/3
>>>> 0 18.89 353.026 ms swapper/9
>>>> 0 18.26 341.190 ms swapper/6
>>>> 0 18.25 341.048 ms swapper/4
>>>> 0 18.13 338.844 ms swapper/10
>>>> 0 18.12 338.686 ms swapper/1
>>>> 0 18.05 337.333 ms swapper/11
>>>> 0 17.92 334.903 ms swapper/7
>>>> 0 17.80 332.691 ms swapper/5
>>>> 0 17.38 324.762 ms swapper/8
>>>> 0 17.29 323.102 ms swapper/0
>>>> 0 16.89 315.630 ms swapper/2
>>>> 2912984 2.10 39.452 ms perf
>>>> 2912985 0.73 14.004 ms sched-messaging
>>>> 660381 0.14 3.527 ms containerd
>>>> 3006112 0.07 1.402 ms redis-server
>>>> 2904655 0.05 1.071 ms kworker/0:0
>>>> 659822 0.03 1.729 ms containerd
>>>> 659824 0.03 1.346 ms containerd
>>>> 1053 0.01 0.353 ms zabbix_agentd
>>>> 2895571 0.01 0.349 ms kworker/8:1
>>>> 10 0.00 0.535 ms rcu_sched
>>>> 2912192 0.00 0.272 ms kworker/u24:2
>>>> 2903540 0.00 0.182 ms sshd
>>>> 801 0.00 0.120 ms jbd2/sda4-8
>>>> 2929605 0.00 0.108 ms grpc_global_tim
>>>> 2912986 0.00 0.075 ms perf
>>>> 2897765 0.00 0.073 ms kworker/7:1
>>>> 2912817 0.00 0.070 ms kworker/2:1
>>>> 391756 0.00 0.067 ms grpc_global_tim
>>>> 2901459 0.00 0.056 ms kworker/3:0
>>>> 2908185 0.00 0.052 ms kworker/10:1
>>>> 2901521 0.00 0.050 ms kworker/6:1
>>>> 2902444 0.00 0.046 ms kworker/5:1
>>>> 2898513 0.00 0.041 ms kworker/1:1
>>>> 2912280 0.00 0.039 ms kworker/11:3
>>>> 1057 0.00 0.037 ms zabbix_agentd
>>>> 2908010 0.00 0.037 ms kworker/9:3
>>>> 2912951 0.00 0.036 ms kworker/4:3
>>>> 793 0.00 0.027 ms multipathd
>>>> 42 0.00 0.023 ms ksoftirqd/5
>>>> 9 0.00 0.022 ms ksoftirqd/0
>>>> 24 0.00 0.019 ms ksoftirqd/2
>>>> 59 0.00 0.019 ms migration/8
>>>> 2929607 0.00 0.018 ms wecode-db
>>>> 29 0.00 0.012 ms migration/3
>>>> 11 0.00 0.012 ms migration/0
>>>> 65 0.00 0.012 ms migration/9
>>>> 17 0.00 0.011 ms migration/1
>>>> 71 0.00 0.011 ms migration/10
>>>> 53 0.00 0.011 ms migration/7
>>>> 23 0.00 0.011 ms migration/2
>>>> 47 0.00 0.011 ms migration/6
>>>> 789 0.00 0.010 ms multipathd
>>>> 35 0.00 0.010 ms migration/4
>>>> 480 0.00 0.009 ms kworker/4:1H
>>>> 41 0.00 0.008 ms migration/5
>>>> 54 0.00 0.006 ms ksoftirqd/7
>>>> 36 0.00 0.005 ms ksoftirqd/4
>>>> 72 0.00 0.005 ms ksoftirqd/10
>>>> 66 0.00 0.005 ms ksoftirqd/9
>>>> 30 0.00 0.004 ms ksoftirqd/3
>>>> 2898362 0.00 0.003 ms kworker/u24:0
>>>>
>>>> # perf kwork top -C 2,4,5
>>>>
>>>> Total : 5604.885 ms, 3 cpus
>>>> %Cpu(s): 17.65% id, 0.00% hi, 0.09% si
>>>> %Cpu2 [|||||||||||||||||||||||| 83.00%]
>>>> %Cpu4 [|||||||||||||||||||||||| 81.66%]
>>>> %Cpu5 [|||||||||||||||||||||||| 82.10%]
>>>>
>>>> PID %CPU RUNTIME COMMMAND
>>>> ----------------------------------------------------
>>>> 0 18.25 341.048 ms swapper/4
>>>> 0 17.80 332.691 ms swapper/5
>>>> 0 16.89 315.630 ms swapper/2
>>>> 2913012 8.99 168.201 ms sched-messaging
>>>> 2913021 8.74 163.456 ms sched-messaging
>>>> 2913026 8.34 156.120 ms sched-messaging
>>>> 2913010 8.14 152.372 ms sched-messaging
>>>> 2913007 7.74 144.754 ms sched-messaging
>>>> 2913016 7.42 138.977 ms sched-messaging
>>>> 2913022 7.28 136.279 ms sched-messaging
>>>> 2913013 7.00 130.894 ms sched-messaging
>>>> 2913019 6.96 130.455 ms sched-messaging
>>>> 2913023 6.91 129.364 ms sched-messaging
>>>> 2913008 6.47 121.331 ms sched-messaging
>>>> 2913018 6.47 121.124 ms sched-messaging
>>>> 2912994 6.42 120.213 ms sched-messaging
>>>> 2913025 6.42 120.140 ms sched-messaging
>>>> 2913020 6.37 119.386 ms sched-messaging
>>>> 2913011 6.35 118.921 ms sched-messaging
>>>> 2913014 6.24 116.779 ms sched-messaging
>>>> 2913009 6.01 112.661 ms sched-messaging
>>>> 2913005 5.96 111.587 ms sched-messaging
>>>> 2913003 5.94 111.142 ms sched-messaging
>>>> 2913024 5.87 109.876 ms sched-messaging
>>>> 2912988 5.84 109.396 ms sched-messaging
>>>> 2912987 5.80 108.550 ms sched-messaging
>>>> 2912990 5.51 103.322 ms sched-messaging
>>>> 2912993 5.45 102.045 ms sched-messaging
>>>> 2912996 5.42 101.622 ms sched-messaging
>>>> 2913006 5.42 101.592 ms sched-messaging
>>>> 2913000 5.41 101.511 ms sched-messaging
>>>> 2913002 5.41 101.420 ms sched-messaging
>>>> 2912997 5.40 101.315 ms sched-messaging
>>>> 2913004 5.33 99.872 ms sched-messaging
>>>> 2913015 5.29 99.252 ms sched-messaging
>>>> 2913017 5.22 97.822 ms sched-messaging
>>>> 2912991 5.11 95.773 ms sched-messaging
>>>> 2912992 5.11 95.579 ms sched-messaging
>>>> 2913001 5.07 95.033 ms sched-messaging
>>>> 2912989 4.93 92.425 ms sched-messaging
>>>> 2912995 4.85 90.892 ms sched-messaging
>>>> 2912998 4.78 89.617 ms sched-messaging
>>>> 2912999 4.56 85.576 ms sched-messaging
>>>> 3006112 0.07 1.402 ms redis-server
>>>> 660381 0.02 0.566 ms containerd
>>>> 2912984 0.02 0.452 ms perf
>>>> 659824 0.01 0.369 ms containerd
>>>> 659822 0.00 0.316 ms containerd
>>>> 10 0.00 0.176 ms rcu_sched
>>>> 801 0.00 0.120 ms jbd2/sda4-8
>>>> 2912985 0.00 0.107 ms sched-messaging
>>>> 2912986 0.00 0.075 ms perf
>>>> 2912817 0.00 0.070 ms kworker/2:1
>>>> 2912192 0.00 0.056 ms kworker/u24:2
>>>> 2929605 0.00 0.046 ms grpc_global_tim
>>>> 2902444 0.00 0.046 ms kworker/5:1
>>>> 2912951 0.00 0.036 ms kworker/4:3
>>>> 42 0.00 0.023 ms ksoftirqd/5
>>>> 24 0.00 0.019 ms ksoftirqd/2
>>>> 23 0.00 0.011 ms migration/2
>>>> 35 0.00 0.010 ms migration/4
>>>> 480 0.00 0.009 ms kworker/4:1H
>>>> 41 0.00 0.008 ms migration/5
>>>> 36 0.00 0.005 ms ksoftirqd/4
>>>>
>>>> # perf kwork top -n perf
>>>>
>>>> Total : 22419.068 ms, 12 cpus
>>>> %Cpu(s): 17.99% id, 0.00% hi, 0.09% si
>>>> %Cpu0 [ 0.00%]
>>>> %Cpu1 [ 0.00%]
>>>> %Cpu2 [ 0.02%]
>>>> %Cpu3 [ 0.00%]
>>>> %Cpu4 [ 0.00%]
>>>> %Cpu5 [ 0.00%]
>>>> %Cpu6 [ 0.00%]
>>>> %Cpu7 [ 0.00%]
>>>> %Cpu8 [ 0.03%]
>>>> %Cpu9 [ 0.09%]
>>>> %Cpu10 [ 0.00%]
>>>> %Cpu11 [ 1.96%]
>>>>
>>>> PID %CPU RUNTIME COMMMAND
>>>> ----------------------------------------------------
>>>> 2912984 2.10 39.452 ms perf
>>>> 2912986 0.00 0.075 ms perf
>>>>
>>>> # perf kwork top -s tid -n sched-messaging
>>>>
>>>> Total : 22419.068 ms, 12 cpus
>>>> %Cpu(s): 17.99% id, 0.00% hi, 0.09% si
>>>> %Cpu0 [|||||||||||||||||||||||| 81.80%]
>>>> %Cpu1 [|||||||||||||||||||||||| 81.65%]
>>>> %Cpu2 [|||||||||||||||||||||||| 82.88%]
>>>> %Cpu3 [|||||||||||||||||||||||| 80.96%]
>>>> %Cpu4 [|||||||||||||||||||||||| 81.64%]
>>>> %Cpu5 [|||||||||||||||||||||||| 82.04%]
>>>> %Cpu6 [|||||||||||||||||||||||| 81.63%]
>>>> %Cpu7 [|||||||||||||||||||||||| 81.97%]
>>>> %Cpu8 [|||||||||||||||||||||||| 82.43%]
>>>> %Cpu9 [|||||||||||||||||||||||| 80.86%]
>>>> %Cpu10 [|||||||||||||||||||||||| 81.72%]
>>>> %Cpu11 [||||||||||||||||||||||| 79.89%]
>>>>
>>>> PID %CPU RUNTIME COMMMAND
>>>> ----------------------------------------------------
>>>> 2912985 0.04 1.111 ms sched-messaging
>>>> 2912987 21.28 398.512 ms sched-messaging
>>>> 2912988 21.44 401.820 ms sched-messaging
>>>> 2912989 21.46 402.303 ms sched-messaging
>>>> 2912990 21.54 403.601 ms sched-messaging
>>>> 2912991 21.59 404.378 ms sched-messaging
>>>> 2912992 21.57 403.845 ms sched-messaging
>>>> 2912993 21.69 406.166 ms sched-messaging
>>>> 2912994 21.52 403.087 ms sched-messaging
>>>> 2912995 21.49 402.421 ms sched-messaging
>>>> 2912996 21.48 402.666 ms sched-messaging
>>>> 2912997 21.27 398.518 ms sched-messaging
>>>> 2912998 21.75 407.579 ms sched-messaging
>>>> 2912999 21.79 407.929 ms sched-messaging
>>>> 2913000 21.78 408.045 ms sched-messaging
>>>> 2913001 21.55 403.803 ms sched-messaging
>>>> 2913002 21.27 398.759 ms sched-messaging
>>>> 2913003 21.46 402.034 ms sched-messaging
>>>> 2913004 21.37 400.242 ms sched-messaging
>>>> 2913005 21.56 403.715 ms sched-messaging
>>>> 2913006 21.23 397.888 ms sched-messaging
>>>> 2913007 27.48 514.411 ms sched-messaging
>>>> 2913008 27.54 515.447 ms sched-messaging
>>>> 2913009 27.30 510.997 ms sched-messaging
>>>> 2913010 27.50 514.890 ms sched-messaging
>>>> 2913011 27.32 511.632 ms sched-messaging
>>>> 2913012 27.30 511.138 ms sched-messaging
>>>> 2913013 27.30 511.109 ms sched-messaging
>>>> 2913014 27.32 511.381 ms sched-messaging
>>>> 2913015 27.36 512.563 ms sched-messaging
>>>> 2913016 27.18 509.231 ms sched-messaging
>>>> 2913017 27.56 516.273 ms sched-messaging
>>>> 2913018 27.56 516.152 ms sched-messaging
>>>> 2913019 27.25 510.488 ms sched-messaging
>>>> 2913020 27.20 509.677 ms sched-messaging
>>>> 2913021 27.23 509.661 ms sched-messaging
>>>> 2913022 27.19 509.061 ms sched-messaging
>>>> 2913023 27.21 509.400 ms sched-messaging
>>>> 2913024 27.18 509.108 ms sched-messaging
>>>> 2913025 27.62 516.976 ms sched-messaging
>>>> 2913026 27.35 512.198 ms sched-messaging
>>>>
>>>> # perf kwork top -b
>>>> Starting trace, Hit <Ctrl+C> to stop and report
>>>> ^C
>>>> Total : 89209.004 ms, 4 cpus
>>>> %Cpu(s): 13.47% id, 0.01% hi, 0.24% si
>>>> %Cpu0 [||||||||||||||||||||||||| 86.08%]
>>>> %Cpu1 [|||||||||||||||||||||||||| 87.08%]
>>>> %Cpu2 [||||||||||||||||||||||||| 86.10%]
>>>> %Cpu3 [||||||||||||||||||||||||| 85.86%]
>>>>
>>>> PID SPID %CPU RUNTIME COMMMAND
>>>> -------------------------------------------------------------
>>>> 0 0 13.86 3092.482 ms [swapper/3]
>>>> 0 0 13.71 3057.756 ms [swapper/0]
>>>> 0 0 13.65 3044.987 ms [swapper/2]
>>>> 0 0 12.63 2818.079 ms [swapper/1]
>>>> 320 320 1.32 295.427 ms bash
>>>> 414 320 1.09 247.658 ms sched-messaging
>>>> 678 320 1.09 246.881 ms sched-messaging
>>>> 354 320 1.09 246.683 ms sched-messaging
>>>> 409 320 1.08 246.839 ms sched-messaging
>>>> 554 320 1.07 243.045 ms sched-messaging
>>>> 405 320 1.04 237.340 ms sched-messaging
>>>> 525 320 1.04 235.718 ms sched-messaging
>>>> 486 320 1.03 235.369 ms sched-messaging
>>>> 714 320 1.03 235.142 ms sched-messaging
>>>> 435 320 1.03 233.290 ms sched-messaging
>>>> 408 320 1.03 231.687 ms sched-messaging
>>>> 716 320 1.02 233.513 ms sched-messaging
>>>> 453 320 1.02 233.181 ms sched-messaging
>>>> 522 320 1.02 230.101 ms sched-messaging
>>>> 651 320 1.02 229.554 ms sched-messaging
>>>> 418 320 1.01 231.359 ms sched-messaging
>>>> 644 320 1.01 229.848 ms sched-messaging
>>>> 535 320 1.01 229.655 ms sched-messaging
>>>> 536 320 1.01 229.147 ms sched-messaging
>>>> 410 320 1.01 227.700 ms sched-messaging
>>>> 689 320 1.00 227.988 ms sched-messaging
>>>> 412 320 1.00 227.052 ms sched-messaging
>>>> 489 320 1.00 226.374 ms sched-messaging
>>>> 521 320 1.00 225.499 ms sched-messaging
>>>> 530 320 1.00 225.262 ms sched-messaging
>>>> 681 320 1.00 225.187 ms sched-messaging
>>>> 415 320 0.99 225.714 ms sched-messaging
>>>> 643 320 0.99 225.090 ms sched-messaging
>>>> 325 320 0.99 223.385 ms sched-messaging
>>>> 498 320 0.99 222.936 ms sched-messaging
>>>> 413 320 0.98 225.213 ms sched-messaging
>>>> 645 320 0.98 223.211 ms sched-messaging
>>>> 544 320 0.98 222.714 ms sched-messaging
>>>> 441 320 0.98 222.590 ms sched-messaging
>>>> 697 320 0.98 222.426 ms sched-messaging
>>>> 523 320 0.98 221.841 ms sched-messaging
>>>> 402 320 0.98 221.776 ms sched-messaging
>>>> <SNIP>
>>>>
>>>> Yang Jihong (16):
>>>> perf kwork: Fix incorrect and missing free atom in work_push_atom()
>>>> perf kwork: Add the supported subcommands to the document
>>>> perf kwork: Set ordered_events for perf_tool
>>>> perf kwork: Add `kwork` and `src_type` to work_init() for struct
>>>> kwork_class
>>>> perf kwork: Overwrite original atom in the list when a new atom is
>>>> pushed.
>>>> perf kwork: Set default events list if not specified in
>>>> setup_event_list()
>>>> perf kwork: Add sched record support
>>>> perf kwork: Add `root` parameter to work_sort()
>>>> perf kwork: Implement perf kwork top
>>>> perf evsel: Add evsel__intval_common() helper
>>>> perf kwork top: Add statistics on hardirq event support
>>>> perf kwork top: Add statistics on softirq event support
>>>> perf kwork top: Add -C/--cpu -i/--input -n/--name -s/--sort --time
>>>> options
>>>> perf kwork top: Implements BPF-based cpu usage statistics
>>>> perf kwork top: Add BPF-based statistics on hardirq event support
>>>> perf kwork top: Add BPF-based statistics on softirq event support
>>>
>>> Besides documentation nits, series:
>>> Reviewed-by: Ian Rogers <irogers@...gle.com>
>>
>> Thanks for reivew.
>>
>>>
>>> Whilst looking at the series, could we clean up
>>> tools/perf/util/kwork.h ? Generally none of the structs are commented.
>>
>> Okay, I'll put up a separate patch and add comments about it.
>>> Some like:
>>> > struct kwork_atom {
>>> struct list_head list;
>>> u64 time;
>>> struct kwork_atom *prev;
>>>
>>> void *page_addr;
>>> unsigned long bit_inpage;
>>> };
>>>
>>> Why is it an atom? Why is there a prev when the kwork_atom is also on
>>> a list (which has a prev) ?
>>>
>> An atom indicates a minimum granularity event.
>> For example, an "irq_hander_entry" event of an IRQ whose irqnum==10 is
>> an atom.
>>
>> The prev member is used to store the sequence of events.
>> For example, the sequence of events is as follows:
>> raise -> entry -> exit
>>
>> Then:
>> entry_atom->prev = raise_atom
>>
>> This relationship needs to be saved because need to calculate latency
>> time and running time at the same time in the "perf kwork timehist"
>
> Thanks Yang, this is good context. Could it be added to the header
Okay, I can submit a separate patch with comments.
> file? I'm also wondering at some point we should start generating
> kerneldoc from comments in the code. I don't know if you want to look
> into kerneldoc style comments.
Of course, would you like to tell me how to do it?
Not just perf kwork, but the whole perf tool code, I can do some work on
this.
>
> Thanks,
> Ian
>
>> Thanks,
>> Yang
>
> .
>
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