linux-kernel - Re: [PATCH v3 0/3] Use update_current_exec

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Date:   Tue, 7 Nov 2023 11:39:42 +0800
From:   Yajun Deng <yajun.deng@...ux.dev>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     mingo@...hat.com, juri.lelli@...hat.com,
        vincent.guittot@...aro.org, dietmar.eggemann@....com,
        rostedt@...dmis.org, bsegall@...gle.com, mgorman@...e.de,
        bristot@...hat.com, vschneid@...hat.com,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 0/3] Use update_current_exec_runtime simplify code


On 2023/11/6 20:35, Peter Zijlstra wrote:
> On Tue, Oct 31, 2023 at 08:59:25PM +0800, Yajun Deng wrote:
>> update_current_exec_runtime would update execution time for each task,
>> we can use update_current_exec_runtime simplify code.
>>
>> The 1st and 2nd patch update update_current_exec_runtime() applies to all
>> callers.
>> The 3rd patch use update_current_exec_runtime simplify update_curr.
>>
>> Yajun Deng (3):
>>    sched: Don't account execution time for task group
>>    sched: Don't trace stat runtime for task group
>>    sched/fair: Simplify update_curr()
>>
>>   kernel/sched/deadline.c  |  4 +---
>>   kernel/sched/fair.c      | 13 +++----------
>>   kernel/sched/rt.c        |  5 ++---
>>   kernel/sched/sched.h     | 11 +++++++----
>>   kernel/sched/stop_task.c |  2 +-
>>   5 files changed, 14 insertions(+), 21 deletions(-)
>
> Hurmph, so I'm having conflicts against this:
>
>    https://lkml.kernel.org/r/54d148a144f26d9559698c4dd82d8859038a7380.1699095159.git.bristot@kernel.org
>
> (obviously).. I've resolved the first patch, which also mostly includes
> the second patch.
>
> However, your second patch isn't entirely right, it now unconditionally
> traces ->vruntime, which isn't the same. Imagine a regular task getting
> a PI boost to RT, in that case ->vruntime will be non-zero and the RT
> task will now be logging a vruntime.
>
> Anyway, that tracepoint doesn't really make sense to me anyway, that is,
> it logs a delta_exec and an absolute vruntime, that's inconsistent.
> Also, a delta vruntime can be easily computed because the weight should
> be known.
>
> I think I'm going to simply remove the vruntime from that tracepoint and
> avoid the whole problem.
>
> This then also makes resolving patch 3 easier.
>
> Let me go squish all this and then I'll post a link to whatever came
> out.


Got it, thanks!