linux-kernel - Re: [PATCH v2 2/2] sched

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: <Zo1omq73-ESGsVVg@slm.duckdns.org>
Date: Tue, 9 Jul 2024 06:43:06 -1000
From: Tejun Heo <tj@...nel.org>
To: Vincent Guittot <vincent.guittot@...aro.org>
Cc: rafael@...nel.org, viresh.kumar@...aro.org, linux-pm@...r.kernel.org,
	void@...ifault.com, linux-kernel@...r.kernel.org,
	kernel-team@...a.com, mingo@...hat.com, peterz@...radead.org,
	David Vernet <dvernet@...a.com>,
	"Rafael J . Wysocki" <rafael.j.wysocki@...el.com>
Subject: Re: [PATCH v2 2/2] sched_ext: Add cpuperf support

Hello,

On Tue, Jul 09, 2024 at 03:36:34PM +0200, Vincent Guittot wrote:
> > I tried this and it's a bit problematic. Migrating out all the tasks do
> > bring the numbers pretty close to zero but the math doesn't work out exactly
> > and it often leaves 1 in the averages. While the fair class is in use, they
> 
> hmm interesting, such remaining small value could be expected for
> load_avg but not with util_avg which is normally a direct propagation.
> Do you have a sequence in particular ?

Oh, I thought it was a byproduct of decay calculations not exactly matching
up between the sum and the components but I haven't really checked. It's
really easy to reproduce. Just boot a kernel with sched_ext enabled (with
some instrumentations added to monitor the util calculation), run some
stress workload to be sure and run a sched_ext scheduler (make -C
tools/sched_ext && tools/sched_ext/build/bin/scx_simple).

Thanks.

-- 
tejun