linux-kernel - Re: [PATCH 10/10] sched/fair: Implement an EEVDF like policy

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Date:   Thu, 09 Mar 2023 05:23:33 +0100
From:   Mike Galbraith <efault@....de>
To:     Peter Zijlstra <peterz@...radead.org>, mingo@...nel.org,
        vincent.guittot@...aro.org
Cc:     linux-kernel@...r.kernel.org, juri.lelli@...hat.com,
        dietmar.eggemann@....com, rostedt@...dmis.org, bsegall@...gle.com,
        mgorman@...e.de, bristot@...hat.com, corbet@....net,
        qyousef@...alina.io, chris.hyser@...cle.com,
        patrick.bellasi@...bug.net, pjt@...gle.com, pavel@....cz,
        qperret@...gle.com, tim.c.chen@...ux.intel.com, joshdon@...gle.com,
        timj@....org, kprateek.nayak@....com, yu.c.chen@...el.com,
        youssefesmat@...omium.org, joel@...lfernandes.org
Subject: Re: [PATCH 10/10] sched/fair: Implement an EEVDF like policy

On Wed, 2023-03-08 at 14:36 +0100, Mike Galbraith wrote:
>
> Remember this little bugger, allegedly distilled from a real
> application control thread starvation issue?
>
> 6.3.0.g8ca09d5-master
> homer:/root # time taskset -c 3 starve      
> expecting to receive 10000000 signals
>
> real    0m24.424s
> user    0m4.468s
> sys     0m18.957s
>
> 6.3.0.g8ca09d5-eevdf
> homer:/root # time taskset -c 3 starve
> expecting to receive 10000000 signals
> zzzzzz
> ^C

Ok, seems there must be a math booboo lurking.

virgin source, 100% hog vs tbench buddy pair, all pinned.

  PID USER      PR  NI    VIRT    RES    SHR S  %CPU  %MEM     TIME+ P COMMAND
 5060 root      20   0    4420    680    680 R 96.01 0.004   0:41.40 3 cpuhog
 5058 root      20   0   25500   1920   1792 S 2.326 0.012   0:01.05 3 tbench
 5059 root      20   0    8796    896    768 R 1.661 0.006   0:00.78 3 tbench_srv

echo NO_PRESERVE_LAG > features

  PID USER      PR  NI    VIRT    RES    SHR S  %CPU  %MEM     TIME+ P COMMAND
 5060 root      20   0    4420    680    680 R 99.33 0.004   1:28.24 3 cpuhog
 5058 root      20   0   25500   1920   1792 R 0.333 0.012   0:01.75 3 tbench
 5059 root      20   0    8796    896    768 S 0.333 0.006   0:01.30 3 tbench_srv