linux-kernel - Re: [PATCH 3/6] sched: Simplify sched_info

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Message-ID: <YJP3JnHzfxs6vMzx@cmpxchg.org>
Date:   Thu, 6 May 2021 10:03:18 -0400
From:   Johannes Weiner <hannes@...xchg.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     tglx@...utronix.de, mingo@...nel.org, juri.lelli@...hat.com,
        vincent.guittot@...aro.org, dietmar.eggemann@....com,
        rostedt@...dmis.org, bsegall@...gle.com, mgorman@...e.de,
        bristot@...hat.com, bsingharora@...il.com, pbonzini@...hat.com,
        maz@...nel.org, linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        riel@...riel.com
Subject: Re: [PATCH 3/6] sched: Simplify sched_info_on()

On Wed, May 05, 2021 at 12:59:43PM +0200, Peter Zijlstra wrote:
> The situation around sched_info is somewhat complicated, it is used by
> sched_stats and delayacct and, indirectly, kvm.
> 
> If SCHEDSTATS=Y (but disabled by default) sched_info_on() is
> unconditionally true -- this is the case for all distro kernel configs
> I checked.
> 
> If for some reason SCHEDSTATS=N, but TASK_DELAY_ACCT=Y, then
> sched_info_on() can return false when delayacct is disabled,
> presumably because there would be no other users left; except kvm is.
> 
> Instead of complicating matters further by accurately accounting
> sched_stat and kvm state, simply unconditionally enable when
> SCHED_INFO=Y, matching the common distro case.
> 
> Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>

Acked-by: Johannes Weiner <hannes@...xchg.org>