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From: Ingo Molnar <mingo@kernel.org>
To: Mike Galbraith <bitbucket@online.de>
Cc: LKML <linux-kernel@vger.kernel.org>, Ingo Molnar <mingo@elte.hu>,
	Peter Zijlstra <a.p.zijlstra@chello.nl>
Subject: Re: [patch] sched: minimalist select_idle_sibling() bouncing cow syndrome fix
Date: Mon, 28 Jan 2013 12:21:45 +0100	[thread overview]
Message-ID: <20130128112145.GA23495@gmail.com> (raw)
In-Reply-To: <1359371965.5783.127.camel@marge.simpson.net>


* Mike Galbraith <bitbucket@online.de> wrote:

> On Mon, 2013-01-28 at 11:53 +0100, Ingo Molnar wrote: 
> > * Mike Galbraith <bitbucket@online.de> wrote:
> > 
> > > If the previous CPU is cache affine and idle, select it.
> > 
> > No objections in principle - but would be nice to have a 
> > changelog with numbers, % of improvement included and so?
> 
> Well, that like was my changelog, guess it needs improvement.
> 
> Take 2.
> 
> sched: minimalist select_idle_sibling() bouncing cow syndrome fix
> 
> If the previous CPU is cache affine and idle, select it.
> 
> The current implementation simply traverses the sd_llc domain,
> taking the first idle CPU encountered, which walks buddy pairs
> hand in hand over the package, inflicting excruciating pain.
> 
> 1 tbench pair (worst case) in a 10 core + SMT package:
> 
> pre   15.22 MB/sec 1 procs
> post 252.01 MB/sec 1 procs

Drool ... :-)

What would be a 'contrarian' test - i.e. a test where this could 
hurt most?

Thanks,

	Ingo

  reply	other threads:[~2013-01-28 11:21 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-01-27  7:50 [patch] sched: minimalist select_idle_sibling() bouncing cow syndrome fix Mike Galbraith
2013-01-28 10:53 ` Ingo Molnar
2013-01-28 11:19   ` Mike Galbraith
2013-01-28 11:21     ` Ingo Molnar [this message]
2013-01-28 11:28       ` Mike Galbraith
2013-02-04 19:25     ` [tip:sched/core] sched: Fix select_idle_sibling() bouncing cow syndrome tip-bot for Mike Galbraith

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