From mboxrd@z Thu Jan  1 00:00:00 1970
From: Waiman Long <longman@redhat.com>
Subject: Re: [PATCH 0/6] Backport rework of deadline bandwidth restoration for
 5.10.y
Date: Sun, 20 Aug 2023 12:24:33 -0400
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References: <20230820152144.517461-1-qyousef@layalina.io>
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To: Qais Yousef <qyousef@layalina.io>, stable@vger.kernel.org
Cc: Juri Lelli <juri.lelli@redhat.com>, Tejun Heo <tj@kernel.org>, Dietmar Eggemann <dietmar.eggemann@arm.com>, Peter Zijlstra <peterz@infradead.org>, Vincent Guittot <vincent.guittot@linaro.org>, Ingo Molnar <mingo@kernel.org>, Hao Luo <haoluo@google.com>, John Stultz <jstultz@google.com>, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org


On 8/20/23 11:21, Qais Yousef wrote:
> This is a backport of the series that fixes the way deadline bandwidth
> restoration is done which is causing noticeable delay on resume path. It also
> converts the cpuset lock back into a mutex which some users on Android too.
> I lack the details but AFAIU the read/write semaphore was slower on high
> contention.

Note that it was a percpu rwsem before this patch series. It was not a 
regular rwsem. Percpu rwsem isn't designed to handle high write lock 
contention. A regular rwsem should be similar to mutex in performance 
when handling high write lock contention.

Cheers,
Longman