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

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Message-ID: <20231025110709.3e28861a@gandalf.local.home>
Date:   Wed, 25 Oct 2023 11:07:09 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        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>
Subject: Re: [POC][RFC][PATCH] sched: Extended Scheduler Time Slice

On Wed, 25 Oct 2023 10:53:38 -0400
Mathieu Desnoyers <mathieu.desnoyers@...icios.com> wrote:

> I don't have an informed opinion on whether the proposed heuristic is a 
> good idea or not, but it should definitely be implemented as an 

If you want to get an informed opinion, you can start here:  ;-)

  Thomas's first reply that had me think about this solution:

    https://lore.kernel.org/lkml/87cyyfxd4k.ffs@tglx/

  My reply that started it:

    https://lore.kernel.org/lkml/20231024103426.4074d319@gandalf.local.home/

> extension to rseq as suggested by Peter. I've even made the whole rseq 
> ABI extensible to accommodate those additional use-cases.
> 
> In the initial rounds of rseq implementation, I even called rseq "kTLS" 
> because I expected it to be extended and eventually become an ABI that 
> contains various per-thread fields which are shared between kernel and 
> userspace.
> 
> So don't let the specific naming of the rseq system call stop you from 
> extending it for other purposes when per-thread shared memory between 
> kernel and userspace is needed. Setting up various per-thread areas like 
> this on thread creation is not free: it requires additional system calls 
> on thread creation. It really makes no sense to have more than one.

Thanks for the feedback Mathieu. This may indeed be the interface I am
looking for.

-- Steve