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Date:   Mon, 6 Nov 2023 13:35:39 +0100
From:   Peter Zijlstra <peterz@infradead.org>
To:     Yajun Deng <yajun.deng@linux.dev>
Cc:     mingo@redhat.com, juri.lelli@redhat.com,
        vincent.guittot@linaro.org, dietmar.eggemann@arm.com,
        rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de,
        bristot@redhat.com, vschneid@redhat.com,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3 0/3] Use update_current_exec_runtime simplify code
Message-ID: <20231106123539.GL8262@noisy.programming.kicks-ass.net>
References: <20231031125928.235685-1-yajun.deng@linux.dev>
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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.