From: Peter Zijlstra <peterz@infradead.org>
To: Valentin Schneider <valentin.schneider@arm.com>
Cc: linux-kernel@vger.kernel.org, mingo@kernel.org,
vincent.guittot@linaro.org, juri.lelli@redhat.com,
Dietmar.Eggemann@arm.com, morten.rasmussen@arm.com,
seto.hidetoshi@jp.fujitsu.com, qperret@google.com
Subject: Re: [PATCH] sched/topology: Don't set SD_BALANCE_WAKE on cpuset domain relax
Date: Tue, 15 Oct 2019 13:34:10 +0200 [thread overview]
Message-ID: <20191015113410.GG2311@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20191014164408.32596-1-valentin.schneider@arm.com>
On Mon, Oct 14, 2019 at 05:44:08PM +0100, Valentin Schneider wrote:
> As pointed out in commit
>
> 182a85f8a119 ("sched: Disable wakeup balancing")
>
> SD_BALANCE_WAKE is a tad too aggressive, and is usually left unset.
>
> However, it turns out cpuset domain relaxation will unconditionally set it
> on domains below the relaxation level. This made sense back when
> SD_BALANCE_WAKE was set unconditionally, but it no longer is the case.
>
> We can improve things slightly by noticing that set_domain_attribute() is
> always called after sd_init(), so rather than setting flags we can rely on
> whatever sd_init() is doing and only clear certain flags when above the
> relaxation level.
>
> While at it, slightly clean up the function and flip the relax level
> check to be more human readable.
>
> Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>
> ---
> I was tempted to put a
>
> Fixes: 182a85f8a119 ("sched: Disable wakeup balancing")
>
> but the SD setup code back then was a mess of SD_INIT() macros which I'm
> not familiar with. It *looks* like the sequence was roughly the same as it
> is now (i.e. set up domain flags, *then* call set_domain_attribute()) but
> I'm not completely sure.
This 'relax' thing is on my list of regrets. It is a terrible thing that
should never have existed.
Are you actually using it or did you just stumble upon it while looking
around there?
next prev parent reply other threads:[~2019-10-15 11:34 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-14 16:44 [PATCH] sched/topology: Don't set SD_BALANCE_WAKE on cpuset domain relax Valentin Schneider
2019-10-15 11:34 ` Peter Zijlstra [this message]
2019-10-15 11:37 ` Valentin Schneider
2019-10-16 8:28 ` Peter Zijlstra
2019-10-18 12:48 ` [tip: sched/core] " tip-bot2 for Valentin Schneider
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