linux-kernel - Re: [Question] The system may be stuck if there is a cpu cgroup cpu.cfs_quato

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Message-ID: <Yr9V755mL6jr20c2@mtj.duckdns.org>
Date:   Sat, 2 Jul 2022 05:15:43 +0900
From:   Tejun Heo <tj@...nel.org>
To:     Benjamin Segall <bsegall@...gle.com>
Cc:     Zhang Qiao <zhangqiao22@...wei.com>, mingo@...hat.com,
        peterz@...radead.org, Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        lizefan.x@...edance.com, hannes@...xchg.org,
        cgroups@...r.kernel.org, lkml <linux-kernel@...r.kernel.org>,
        vschneid@...hat.com, dietmar.eggemann@....com, bristot@...hat.com,
        Steven Rostedt <rostedt@...dmis.org>, mgorman@...e.de
Subject: Re: [Question] The system may be stuck if there is a cpu cgroup
 cpu.cfs_quato_us is very low

On Fri, Jul 01, 2022 at 01:08:21PM -0700, Benjamin Segall wrote:
> Yes, fixing (kernel) priority inversion due to CFS_BANDWIDTH requires a
> serious reworking of how it works, because it would need to dequeue
> tasks individually rather than doing the entire cfs_rq at a time (and
> would require some effort to avoid pinging every throttling task to get
> it into the kernel).

Right, I don't have a good idea on evolving the current implementation
into something correct. As you pointed out, we need to account along
the sched_group tree but conditionally enforce on each thread.

Thanks.

-- 
tejun