linux-kernel - Re: [PATCH 6/6] cgroup/cpuset: Iterate only if DEADLINE tasks are present

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Date:   Wed, 26 Apr 2023 13:58:55 +0200
From:   Juri Lelli <juri.lelli@...hat.com>
To:     Qais Yousef <qyousef@...alina.io>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>,
        Waiman Long <longman@...hat.com>, Tejun Heo <tj@...nel.org>,
        Zefan Li <lizefan.x@...edance.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Hao Luo <haoluo@...gle.com>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Steven Rostedt <rostedt@...dmis.org>,
        linux-kernel@...r.kernel.org, luca.abeni@...tannapisa.it,
        claudio@...dence.eu.com, tommaso.cucinotta@...tannapisa.it,
        bristot@...hat.com, mathieu.poirier@...aro.org,
        cgroups@...r.kernel.org,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Wei Wang <wvw@...gle.com>, Rick Yiu <rickyiu@...gle.com>,
        Quentin Perret <qperret@...gle.com>,
        Heiko Carstens <hca@...ux.ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Alexander Gordeev <agordeev@...ux.ibm.com>,
        Sudeep Holla <sudeep.holla@....com>
Subject: Re: [PATCH 6/6] cgroup/cpuset: Iterate only if DEADLINE tasks are
 present

On 04/04/23 21:06, Qais Yousef wrote:
> On 03/29/23 14:55, Juri Lelli wrote:
> > update_tasks_root_domain currently iterates over all tasks even if no
> > DEADLINE task is present on the cpuset/root domain for which bandwidth
> > accounting is being rebuilt. This has been reported to introduce 10+ ms
> > delays on suspend-resume operations.
> > 
> > Skip the costly iteration for cpusets that don't contain DEADLINE tasks.
> > 
> > Reported-by: Qais Yousef <qyousef@...alina.io>
> > Link: https://lore.kernel.org/lkml/20230206221428.2125324-1-qyousef@layalina.io/
> > Signed-off-by: Juri Lelli <juri.lelli@...hat.com>
> > ---
> 
> Wouldn't this be better placed as patch 4? The two fixes from Dietmar look
> orthogonal to me to the accounting problem. But it seems the whole lot needs to
> go to stable anyway, so good to keep them together. Should Dietmar fixes be at
> the end instead of this?

That should be an easy fixing indeed. Dietmar is working on refreshig
his bits.

Thanks for your reviews and tests Qais!

Best,
Juri