From: "Michal Koutný" <mkoutny@suse.com>
To: Valentin Schneider <valentin.schneider@arm.com>
Cc: linux-kernel@vger.kernel.org, cgroups@vger.kernel.org,
lizefan@huawei.com, tj@kernel.org, hannes@cmpxchg.org,
mingo@kernel.org, peterz@infradead.org,
vincent.guittot@linaro.org, Dietmar.Eggemann@arm.com,
morten.rasmussen@arm.com, qperret@google.com
Subject: Re: [PATCH v2] sched/topology, cpuset: Account for housekeeping CPUs to avoid empty cpumasks
Date: Fri, 15 Nov 2019 18:18:07 +0100 [thread overview]
Message-ID: <20191115171807.GH19372@blackbody.suse.cz> (raw)
In-Reply-To: <d7ed40aa-1ac1-a42d-51eb-b1bd9f839fb1@arm.com>
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Hello.
On Thu, Nov 14, 2019 at 04:03:50PM +0000, Valentin Schneider <valentin.schneider@arm.com> wrote:
> Michal, could I nag you for a reviewed-by? I'd feel a bit more confident
> with any sort of approval from folks who actually do use cpusets.
TL;DR I played with the v5.4-rc6 _without_ this fixup and I conclude it
unnecessary (IOW my previous theoretical observation was wrong).
The original problem is non-issue with v2 cpuset controller, because
effective_cpus are never empty. isolcpus doesn't take out cpuset CPUs,
hotplug does. In the case, no online CPU remains in the cpuset, it
inherits ancestor's non-empty cpuset.
I reproduced the problem with v1 (before your fix). However, in v1
effective == allowed (we're destructive and overwrite allowed on
hotunplug) and we already check the emptiness of
cpumask_intersects(cp->cpus_allowed, housekeeping_cpumask(HK_FLAG_DOMAIN)
few lines higher. I.e. the fixup adds redundant check against the empty
sched domain production.
Sorry for the noise and HTH,
Michal
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next prev parent reply other threads:[~2019-11-15 17:18 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-04 0:39 [PATCH v2] sched/topology, cpuset: Account for housekeeping CPUs to avoid empty cpumasks Valentin Schneider
2019-11-04 0:47 ` Valentin Schneider
2019-11-14 16:03 ` Valentin Schneider
2019-11-15 17:18 ` Michal Koutný [this message]
2019-11-15 18:48 ` Valentin Schneider
2019-11-15 18:13 ` [tip: sched/urgent] " tip-bot2 for Valentin Schneider
2019-11-15 18:15 ` Valentin Schneider
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