linux-kernel - Re: [RFC PATCH v4 0/2] sched/fair: Choose the CPU where short task is running during wake up

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Date:   Mon, 23 Jan 2023 10:17:46 +0530
From:   K Prateek Nayak <kprateek.nayak@....com>
To:     Chen Yu <yu.c.chen@...el.com>, Yicong Yang <yangyicong@...wei.com>
Cc:     yangyicong@...ilicon.com, Peter Zijlstra <peterz@...radead.org>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Tim Chen <tim.c.chen@...el.com>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Juri Lelli <juri.lelli@...hat.com>,
        Rik van Riel <riel@...riel.com>,
        Aaron Lu <aaron.lu@...el.com>,
        Abel Wu <wuyun.abel@...edance.com>,
        "Gautham R . Shenoy" <gautham.shenoy@....com>,
        Ingo Molnar <mingo@...hat.com>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ben Segall <bsegall@...gle.com>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Valentin Schneider <vschneid@...hat.com>,
        Hillf Danton <hdanton@...a.com>,
        Honglei Wang <wanghonglei@...ichuxing.com>,
        Len Brown <len.brown@...el.com>,
        Chen Yu <yu.chen.surf@...il.com>,
        Tianchen Ding <dtcccc@...ux.alibaba.com>,
        Joel Fernandes <joel@...lfernandes.org>,
        Josh Don <joshdon@...gle.com>, Barry Song <21cnbao@...il.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH v4 0/2] sched/fair: Choose the CPU where short task is
 running during wake up

Hello Chenyu,

Thank you for looking into this.

On 1/22/2023 9:07 PM, Chen Yu wrote:
> On 2023-01-20 at 17:09:28 +0800, Yicong Yang wrote:
> [..snip..]
>
> This sounds reasonable to me. I think we can further enhance it.
> And before you sending out the proposal, could you help test the following
> experimental change, to see if it makes tbench netperf and MySQL better?
> 
> Hi Prateek, could you also help check if below change would make the Spec regression
> go away?

Sure. I'll add this on top of v4 and queue some runs.
Will share the results soon.

> 
> thanks,
> Chenyu
> 
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index fc8a636eca5e..6e1ab5e2686c 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -4974,7 +4974,7 @@ wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se);
>  static inline int is_short_task(struct task_struct *p)
>  {
>  	return sched_feat(SIS_SHORT) && p->se.dur_avg &&
> -		((p->se.dur_avg * 8) <= sysctl_sched_min_granularity);
> +		((p->se.dur_avg * 1024) <= (__this_cpu_read(sd_llc_size) * sysctl_sched_min_granularity));
>  }
>  
>  /*


--
Thanks and Regards,
Prateek