linux-kernel - Re: [PATCH 19/24] sched/eevdf: Fixup PELT vs DELAYED

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20240817230636.GB20319@noisy.programming.kicks-ass.net>
Date: Sun, 18 Aug 2024 01:06:36 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: Vincent Guittot <vincent.guittot@...aro.org>
Cc: Valentin Schneider <vschneid@...hat.com>, mingo@...hat.com,
	juri.lelli@...hat.com, dietmar.eggemann@....com,
	rostedt@...dmis.org, bsegall@...gle.com, mgorman@...e.de,
	linux-kernel@...r.kernel.org, kprateek.nayak@....com,
	wuyun.abel@...edance.com, youssefesmat@...omium.org,
	tglx@...utronix.de, efault@....de
Subject: Re: [PATCH 19/24] sched/eevdf: Fixup PELT vs DELAYED_DEQUEUE

On Wed, Aug 14, 2024 at 02:59:00PM +0200, Vincent Guittot wrote:

> > So the whole reason to keep then enqueued is so that they can continue
> > to compete for vruntime, and vruntime is load based. So it would be very
> > weird to remove them from load.
> 
> We only use the weight to update vruntime, not the load. The load is
> used to balance tasks between cpus and if we keep a "delayed" dequeued
> task in the load, we will artificially inflate the load_avg on this rq

So far load has been a direct sum of all weight. Additionally, we delay
until a task gets picked again, migrating tasks to other CPUs will
expedite this condition.

Anyway, at the moment I don't have strong evidence either which way, and
the above argument seem to suggest not changing things for now.

We can always re-evaluate.