linux-kernel - Re: [POC][RFC][PATCH] sched: Extended Scheduler Time Slice

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Date:   Wed, 25 Oct 2023 11:12:47 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Ankur Arora <ankur.a.arora@...cle.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        linux-mm@...ck.org, x86@...nel.org, akpm@...ux-foundation.org,
        luto@...nel.org, bp@...en8.de, dave.hansen@...ux.intel.com,
        hpa@...or.com, mingo@...hat.com, juri.lelli@...hat.com,
        vincent.guittot@...aro.org, willy@...radead.org, mgorman@...e.de,
        jon.grimm@....com, bharata@....com, raghavendra.kt@....com,
        boris.ostrovsky@...cle.com, konrad.wilk@...cle.com,
        jgross@...e.com, andrew.cooper3@...rix.com,
        Joel Fernandes <joel@...lfernandes.org>,
        Youssef Esmat <youssefesmat@...omium.org>,
        Vineeth Pillai <vineethrp@...gle.com>,
        Suleiman Souhlal <suleiman@...gle.com>,
        Ingo Molnar <mingo@...nel.org>,
        Daniel Bristot de Oliveira <bristot@...nel.org>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Subject: Re: [POC][RFC][PATCH] sched: Extended Scheduler Time Slice

On Wed, 25 Oct 2023 05:42:19 -0400
Steven Rostedt <rostedt@...dmis.org> wrote:

> I ran a traceeval tool on it (still work in progress, but I can post when
> it's done), and with the following trace, and the writes to trace-marker
> (tracefs_printf)
> 
>  trace-cmd record -e sched_switch ./extend-sched
> 
> It showed that without the extend, each task was preempted while holding
> the lock around 200 times. With the extend, only one task was ever
> preempted while holding the lock, and it only happened once!

And looking at the trace, it was because it was preempted by an RT task.

    extend-sched-3349  [007]  3309.320747: print:                tracing_mark_write: Have lock!
    extend-sched-3349  [007]  3309.320751: sched_switch:         extend-sched:3349 [120] R ==> migration/7:68 [0]
     migration/7-68    [007]  3309.320754: sched_switch:         migration/7:68 [0] S ==> extend-sched:3349 [120]
    extend-sched-3349  [007]  3309.320756: print:                tracing_mark_write: released lock!

So we know that part of the code works. ;-)

-- Steve