linux-kernel - Re: [RFC PATCH v5] sched/fair: select idle cpu from idle cpumask for task wakeup

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Message-ID: <20201207155015.GQ3040@hirez.programming.kicks-ass.net>
Date:   Mon, 7 Dec 2020 16:50:15 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Aubrey Li <aubrey.li@...ux.intel.com>
Cc:     mingo@...hat.com, juri.lelli@...hat.com,
        vincent.guittot@...aro.org, mgorman@...hsingularity.net,
        valentin.schneider@....com, qais.yousef@....com,
        dietmar.eggemann@....com, rostedt@...dmis.org, bsegall@...gle.com,
        tim.c.chen@...ux.intel.com, linux-kernel@...r.kernel.org,
        Mel Gorman <mgorman@...e.de>, Jiang Biao <benbjiang@...il.com>
Subject: Re: [RFC PATCH v5] sched/fair: select idle cpu from idle cpumask for
 task wakeup

On Wed, Nov 18, 2020 at 12:31:13PM +0800, Aubrey Li wrote:
> Add idle cpumask to track idle cpus in sched domain. When a CPU
> enters idle, if the idle driver indicates to stop tick, this CPU
> is set in the idle cpumask to be a wakeup target. And if the CPU
> is not in idle, the CPU is cleared in idle cpumask during scheduler
> tick to ratelimit idle cpumask update.

So this will only have SIS consider CPUs that have the tick stopped?
That might affect the facebook tail-latency workloads quite a bit.