linux-kernel - Re: [patch] CFS scheduler, -v5

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Message-ID: <20070423092502.GA7972@elte.hu>
Date:	Mon, 23 Apr 2007 11:25:02 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Nick Piggin <npiggin@...e.de>
Cc:	linux-kernel@...r.kernel.org,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Con Kolivas <kernel@...ivas.org>,
	Mike Galbraith <efault@....de>,
	Arjan van de Ven <arjan@...radead.org>,
	Peter Williams <pwil3058@...pond.net.au>,
	Thomas Gleixner <tglx@...utronix.de>, caglar@...dus.org.tr,
	Willy Tarreau <w@....eu>,
	Gene Heskett <gene.heskett@...il.com>, Mark Lord <lkml@....ca>,
	Ulrich Drepper <drepper@...hat.com>
Subject: Re: [patch] CFS scheduler, -v5


* Nick Piggin <npiggin@...e.de> wrote:

> > yeah - but they'll all be quad core, so the SMP timeslice 
> > multiplicator should do the trick. Most of the CFS testers use 
> > single-CPU systems.
> 
> But desktop users could have have quad thread and even 8 thread CPUs 
> soon, [...]

SMT is indeed an issue, so i think what should be used to scale 
timeslices isnt num_online_cpus(), but the sum of all CPU's ->cpu_power 
value (scaled down by SCHED_LOAD_SCALE). That way if the thread is not a 
'full CPU', then the scaling will be proportionally smaller. Can you see 
any hole in that?

	Ingo
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