linux-kernel - Re: [patch] CFS scheduler, v3

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Message-ID: <20070424174226.GE5475@linux-os.sc.intel.com>
Date:	Tue, 24 Apr 2007 10:42:27 -0700
From:	"Siddha, Suresh B" <suresh.b.siddha@...el.com>
To:	Christoph Lameter <clameter@....com>
Cc:	"Siddha, Suresh B" <suresh.b.siddha@...el.com>,
	William Lee Irwin III <wli@...omorphy.com>,
	Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Con Kolivas <kernel@...ivas.org>,
	Nick Piggin <npiggin@...e.de>, 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>
Subject: Re: [patch] CFS scheduler, v3

On Tue, Apr 24, 2007 at 10:39:48AM -0700, Christoph Lameter wrote:
> On Fri, 20 Apr 2007, Siddha, Suresh B wrote:
> 
> > > Last I checked it was workload-dependent, but there were things that
> > > hammer it. I mostly know of the remote wakeup issue, but there could
> > > be other things besides wakeups that do it, too.
> > 
> > remote wakeup was the main issue and the 0.5% improvement was seen
> > on a two node platform. Aligning it reduces the number of remote
> > cachelines that needs to be touched as part of this wakeup.
> 
> .5% is usually in the noise ratio. Are you consistently seeing an 
> improvement or is that sporadic?

No. This is consistent. I am waiting for the perf data on a much much bigger
NUMA box.

Anyhow, this is a straight forward optimization and needs to be done. Do you
have any specific concerns?

thanks,
suresh
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