linux-kernel - Re: SCHED: Is task migration necessary in sched

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Message-ID: <1261570834.4937.141.camel@laptop>
Date:	Wed, 23 Dec 2009 13:20:34 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Rakib Mullick <rakib.mullick@...il.com>
Cc:	Ingo Molnar <mingo@...e.hu>, LKML <linux-kernel@...r.kernel.org>
Subject: Re: SCHED: Is task migration necessary in sched_exec().

On Wed, 2009-12-23 at 18:04 +0600, Rakib Mullick wrote:
> On 12/23/09, Peter Zijlstra <peterz@...radead.org> wrote:
> > On Wed, 2009-12-23 at 17:35 +0600, Rakib Mullick wrote:
> 
> >  Do you have a particular workload you worry about or are you merely
> >  trying to satisfy your curiosity?
> >
> No, I don't have any particular workload.

Anyway, look at it this way, suppose you have 4 tasks on 2 cpus, cpu0
has 3 tasks and cpu1 has 1 task.

The currently running task on cpu0 does exec and gets moved to cpu1,
even though it gives up time on cpu0, it gains time on cpu1. Because it
was eligible to 1/3 of cpu0's time, whereas it is eligible to 1/2 of
cpu1's time.

So its a win, right?

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