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: <CA+55aFwe_LBm9bJ2FhjOq1Ae0hu7Sd4F4yZMMXd7BnSFu+RvAg@mail.gmail.com>
Date:	Mon, 24 Sep 2012 20:10:08 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Mike Galbraith <efault@....de>
Cc:	Borislav Petkov <bp@...en8.de>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Mel Gorman <mgorman@...e.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, Sep 24, 2012 at 7:49 PM, Mike Galbraith <efault@....de> wrote:
>
> Ah.  That's what I did to select_idle_sibling() in a nutshell, converted
> the problematic large L3 packages into multiple ~core2duo pairs, modulo
> shared L2 'course.  Bounce proof, and on Westmere, the jabbering back
> and forth in L3 somehow doesn't hurt as much as expected, so the things
> act (more or less, L2 traffic _does_ matter;) like the real deal.

Right. But your patch *only* looked at the pair.

Which may be bounce-proof, but we also saw that it was unacceptable.

              Linus
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