From: Peter Zijlstra <peterz@infradead.org>
To: Rakib Mullick <rakib.mullick@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>, LKML <linux-kernel@vger.kernel.org>
Subject: Re: SCHED: Is task migration necessary in sched_exec().
Date: Wed, 23 Dec 2009 11:53:04 +0100 [thread overview]
Message-ID: <1261565584.4937.124.camel@laptop> (raw)
In-Reply-To: <b9df5fa10912230246w4adf160bibc12d7c6480ce058@mail.gmail.com>
On Wed, 2009-12-23 at 16:46 +0600, Rakib Mullick wrote:
> On 12/23/09, Peter Zijlstra <peterz@infradead.org> wrote:
> > On Wed, 2009-12-23 at 16:14 +0600, Rakib Mullick wrote:
> >
> >
> > Well, if there's an imbalance the 'slow' load-balancer will move it
> > around eventually anyway, and since it will then have build up a larger
> > cache footprint it will be even more expensive.
> >
> If there is an imbalance - then the overloaded task will moved.
There is no overloaded task, its the runqueue that is overloaded wrt to
other runqueues. The load-balancer has to pick a 'random' task and pray.
Current heuristics try to pick a task that hasn't been on the cpu for a
while, because for those the effective cache footprint is minimal.
> Why the _current_ task?
Because at exec it has effective 0 cache footprint, and is thus an ideal
victim to move about.
next prev parent reply other threads:[~2009-12-23 10:53 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-12-23 10:14 SCHED: Is task migration necessary in sched_exec() Rakib Mullick
2009-12-23 10:21 ` Peter Zijlstra
2009-12-23 10:46 ` Rakib Mullick
2009-12-23 10:53 ` Peter Zijlstra [this message]
2009-12-23 11:35 ` Rakib Mullick
2009-12-23 11:51 ` Peter Zijlstra
2009-12-23 12:04 ` Rakib Mullick
2009-12-23 12:20 ` Peter Zijlstra
2009-12-23 12:52 ` Rakib Mullick
2009-12-23 18:06 ` Peter Zijlstra
2009-12-25 2:53 ` Rakib Mullick
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