linux-kernel - Re: CFS Scheduler : Period : for NCPUs : Code Suggestion Change

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Date:	Mon, 06 Jul 2009 14:46:20 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Mitchell Erblich <erblichs@...thlink.net>
Cc:	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...e.hu>
Subject: Re: CFS Scheduler : Period : for NCPUs : Code Suggestion Change

On Tue, 2009-06-30 at 18:36 -0700, Mitchell Erblich wrote:
> This is NOT A PATCH.
> 
> 	PLEASE include my email in the reply as I am not currently on
> 	the linux kernel mail alias.
> 
> 	This code snap is grabbed from what is believed to be a semi-current
> 	OS source (fxr.watson.org) comparison webpage.
> 
> 	Upon a quick CFS scheduler code walk, increasing the period
> 	should ALSO be dependent on the number of online/active CPUs.
> 
> 	The period should be adjusted based on the number of
> 	online CPUs. This change allows NCPUs * tasks without
> 	changing/increasing the period.
> 
> 	On first thought NR_CPUS should give the number of cpu on
> 	the system, however, this may be different from the number of
> 	CPUs online, thus..
> 
> 	Change #1: place after line 425
> 	int cpu, ncpu;
> 
> 
> 	Change #2: place before line 427
> 	for_each_online_cpu(cpu) {
> 		ncpu++;
>          }
> 	nr_running /=  ncpu;
> 	

Ah, but the nr_running number used is _per_ cpu already, so would that
address your concern?

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