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Date:   Tue, 22 Nov 2022 11:35:48 +0100
From:   Peter Zijlstra <peterz@infradead.org>
To:     Josh Don <joshdon@google.com>
Cc:     Chengming Zhou <zhouchengming@bytedance.com>,
        Ingo Molnar <mingo@redhat.com>,
        Juri Lelli <juri.lelli@redhat.com>,
        Vincent Guittot <vincent.guittot@linaro.org>,
        Dietmar Eggemann <dietmar.eggemann@arm.com>,
        Steven Rostedt <rostedt@goodmis.org>,
        Ben Segall <bsegall@google.com>, Mel Gorman <mgorman@suse.de>,
        Daniel Bristot de Oliveira <bristot@redhat.com>,
        Valentin Schneider <vschneid@redhat.com>,
        linux-kernel@vger.kernel.org, Tejun Heo <tj@kernel.org>,
        Michal =?iso-8859-1?Q?Koutn=FD?= <mkoutny@suse.com>,
        Christian Brauner <brauner@kernel.org>,
        Zefan Li <lizefan.x@bytedance.com>
Subject: Re: [PATCH v3] sched: async unthrottling for cfs bandwidth
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On Mon, Nov 21, 2022 at 11:37:14AM -0800, Josh Don wrote:
> Yep, this tradeoff feels "best", but there are some edge cases where
> this could potentially disrupt fairness. For example, if we have
> non-trivial W, a lot of cpus to iterate through for dispatching remote
> unthrottle, and quota is small. Doesn't help that the timer is pinned
> so that this will continually hit the same cpu.

We could -- if we wanted to -- manually rotate the timer around the
relevant CPUs. Doing that sanely would require a bit of hrtimer surgery
though I'm afraid.