linux-kernel - Re: 20% performance drop on PostgreSQL 9.2 from kernel 3.5.3 to 3.6-rc5 on AMD chipsets

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Message-ID: <1348511193.6951.44.camel@marge.simpson.net>
Date:	Mon, 24 Sep 2012 20:26:33 +0200
From:	Mike Galbraith <efault@....de>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Mel Gorman <mgorman@...e.de>, Borislav Petkov <bp@...en8.de>,
	Nikolay Ulyanitsky <lystor@...il.com>,
	linux-kernel@...r.kernel.org,
	Andreas Herrmann <andreas.herrmann3@....com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...nel.org>,
	Suresh Siddha <suresh.b.siddha@...el.com>
Subject: Re: 20% performance drop on PostgreSQL 9.2 from kernel 3.5.3 to
 3.6-rc5 on AMD chipsets - bisected

On Mon, 2012-09-24 at 18:54 +0200, Peter Zijlstra wrote: 
> On Mon, 2012-09-24 at 09:30 -0700, Linus Torvalds wrote:

> > Also, do we really want to spread things out that aggressively?
> > How/why do we know that we don't want to share L2 caches, for example?
> > It sounds like a bad idea from a power standpoint, and possibly
> > performance too.
> 
> IIRC this current stuff is the result of Mike and Suresh running a few
> benchmarks.. Mike, Suresh, either one of you remember this? Otherwise
> I'll have to go trawl the archives.

Aside from the cache pollution I recall having been mentioned, on my
E5620, cross core is a tbench win over affine, cross thread is not.

-Mike

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