Re: [patch] CFS scheduler, v3

From: Siddha, Suresh B
Date: Tue Apr 24 2007 - 11:06:44 EST

On Fri, Apr 20, 2007 at 01:03:22PM -0700, William Lee Irwin III wrote:
> On Fri, 20 Apr 2007, William Lee Irwin III wrote:
> >> I'm not really convinced it's all that worthwhile of an optimization,
> >> essentially for the same reasons as you, but presumably there's a
> >> benchmark result somewhere that says it matters. I've just not seen it.
> On Fri, Apr 20, 2007 at 12:44:55PM -0700, Christoph Lameter wrote:
> > If it is true that we frequently remotely write the per cpu runqueue
> > data then we may have a NUMA scalability issue.
> From the discussion on Suresh's thread, it appears to have sped up a
> database benchmark 0.5%.
> 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.

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