linux-kernel - Re: [PATCH 2/2] sched/core: Uncookied force idle accounting per cpu

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Message-ID: <CABk29Nt9TMyQJWSYRzWMmmHpT5z85npganZKAF9vkBqJWDhx6Q@mail.gmail.com>
Date:   Thu, 6 Jan 2022 12:03:21 -0800
From:   Josh Don <joshdon@...gle.com>
To:     cruzzhao <cruzzhao@...ux.alibaba.com>
Cc:     Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Benjamin Segall <bsegall@...gle.com>,
        Mel Gorman <mgorman@...e.de>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Alexey Dobriyan <adobriyan@...il.com>,
        Eric Dumazet <edumazet@...gle.com>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>
Subject: Re: [PATCH 2/2] sched/core: Uncookied force idle accounting per cpu

On Thu, Jan 6, 2022 at 4:05 AM cruzzhao <cruzzhao@...ux.alibaba.com> wrote:
>
>
> 在 2022/1/6 上午4:59, Josh Don 写道:
>
> It's a good idea to combine them into a single sum. I separated them in
> order to be consistent with the task accounting and for easy to understand.
> As for change the task accounting, I've tried but I haven't found a
> proper method to do so. I've considered the following methods:
> 1. Account the uncookie'd force idle time to the uncookie'd task, but
> it'll be hard to trace the uncookie'd task.

Not sure what you mean there, I think you just need to add

--- a/kernel/sched/core_sched.c
+++ b/kernel/sched/core_sched.c
@@ -294,7 +294,7 @@ void sched_core_account_forceidle(struct rq *rq)
                rq_i = cpu_rq(i);
                p = rq_i->core_pick ?: rq_i->curr;

-               if (!p->core_cookie)
+               if (p == rq_i->idle)
                        continue;

                __schedstat_add(p->stats.core_forceidle_sum, delta)

> 2. Account the uncookie'd force idle time to the cookie'd task in the
> core_tree of the core, but it will cost a lot on traversing the core_tree.
>
> Many thanks for suggestions.
> Best,
> Cruz Zhao
>
> > Why do you need this separated out into two fields then? Could we just
> > combine the uncookie'd and cookie'd forced idle into a single sum?
> >
> > IMO it is fine to account the forced idle from uncookie'd tasks, but
> > we should then also change the task accounting to do the same, for
> > consistency.