linux-kernel - Re: [PATCH 08/17] sched/fair: Implement an EEVDF like policy

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Message-ID: <20230329081814.GN4253@hirez.programming.kicks-ass.net>
Date:   Wed, 29 Mar 2023 10:18:14 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Josh Don <joshdon@...gle.com>
Cc:     mingo@...nel.org, vincent.guittot@...aro.org,
        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, timj@....org,
        kprateek.nayak@....com, yu.c.chen@...el.com,
        youssefesmat@...omium.org, joel@...lfernandes.org, efault@....de
Subject: Re: [PATCH 08/17] sched/fair: Implement an EEVDF like policy

On Tue, Mar 28, 2023 at 06:26:51PM -0700, Josh Don wrote:
> Hi Peter,
> 
> This is a really interesting proposal and in general I think the
> incorporation of latency/deadline is quite a nice enhancement. We've
> struggled for a while to get better latency bounds on performance
> sensitive threads in the face of antagonism from overcommit.

Right; so the big caveat is of course that these are virtual deadlines,
overcommit *will* push them out.

We have SCHED_DEADLINE that does the 'real' deadline thing ;-)

But what these virtual deadlines do is provide an order inside the
virtual time domain. It makes the whole preemption business well
defined. And with that, provides means to mix varying request sizes.