Re: [PATCH v3] perf sched: Fix sched latency analysis incorrect

[Chunxin Zang]

> On Mar 28, 2023, at 03:00, Namhyung Kim <namhyung@xxxxxxxxxx> wrote:
> 
> On Thu, Mar 16, 2023 at 11:33 PM Chunxin Zang <zangchunxin@xxxxxxxxxxx> wrote:
>> 
>> 'perf sched latency' is incorrect to get process schedule latency
>> when it used 'sched:sched_wakeup' to analysis perf.data.
>> 
>> Because 'perf record' prefer use 'sched:sched_waking' to
>> 'sched:sched_wakeup' since commit d566a9c2d482 ("perf sched: Prefer
>> sched_waking event when it exists"). It's very reasonable to
>> evaluate process schedule latency.
>> 
>> Similarly, update sched latency/map/replay to use sched_waking events.
> 
> Have you checked perf sched replay (add_sched_event_wakeup)?  I think
> it'd make unnecessary sched atoms for sched_wakeup.
> 
> Can we check the wakeup and waking events and disable the wakeup
> if the waking is found like in perf_sched__timehist?

That's a good idea, I will do that in v4 version.

Best regards
Chunxin

> 
> Thanks,
> Namhyung
> 
> 
>> 
>> I used 'perf record -e "sched:* "' to record both wakeup and waking events,
>> and use fixed perf version to analysis them, the result is correct.
>> Because the function "latency_wakeup_event" will change atom->state to
>> THREAD_WAIT_CPU at waking event, and judge the 'atom->state !=
>> THREAD_SLEEPING' is false then returned at wakeup event.
>> 
>> Signed-off-by: Chunxin Zang <zangchunxin@xxxxxxxxxxx>
>> Signed-off-by: Jerry Zhou <zhouchunhua@xxxxxxxxxxx>
>> ---
>> 
>>        changelogs in v3:
>>        1) fix non-ASCII characters in commit log.
>> 
>>        changelogs in v2:
>>        1) fix email address disappearing in 'signed off by'
>> 
>> tools/perf/builtin-sched.c | 1 +
>> 1 file changed, 1 insertion(+)
>> 
>> diff --git a/tools/perf/builtin-sched.c b/tools/perf/builtin-sched.c
>> index 86e18575c9be..1af4ec1ac824 100644
>> --- a/tools/perf/builtin-sched.c
>> +++ b/tools/perf/builtin-sched.c
>> @@ -1819,6 +1819,7 @@ static int perf_sched__read_events(struct perf_sched *sched)
>>        const struct evsel_str_handler handlers[] = {
>>                { "sched:sched_switch",       process_sched_switch_event, },
>>                { "sched:sched_stat_runtime", process_sched_runtime_event, },
>> +               { "sched:sched_waking",       process_sched_wakeup_event, },
>>                { "sched:sched_wakeup",       process_sched_wakeup_event, },
>>                { "sched:sched_wakeup_new",   process_sched_wakeup_event, },
>>                { "sched:sched_migrate_task", process_sched_migrate_task_event, },
>> --
>> 2.25.1
>> 
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声明：这封邮件只允许文件接收者阅读，有很高的机密性要求。禁止其他人使用、打开、复制或转发里面的任何内容。如果本邮件错误地发给了你，请联系邮件发出者并删除这个文件。机密及法律的特权并不因为误发邮件而放弃或丧失。任何提出的观点或意见只属于作者的个人见解，并不一定代表本公司。