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Date: Mon, 24 Sep 2012 21:20:56 +0200
From: Borislav Petkov <bp@alien8.de>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>, Peter Zijlstra <a.p.zijlstra@chello.nl>,
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        Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@kernel.org>,
        Suresh Siddha <suresh.b.siddha@intel.com>
Subject: Re: 20% performance drop on PostgreSQL 9.2 from kernel 3.5.3 to
 3.6-rc5 on AMD chipsets - bisected
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On Mon, Sep 24, 2012 at 12:12:18PM -0700, Linus Torvalds wrote:
> On Mon, Sep 24, 2012 at 11:26 AM, Mike Galbraith <efault@gmx.de> wrote:
> >
> > 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.
> 
> Oh, I agree with trying to avoid HT threads, the resource contention
> easily gets too bad.
> 
> It's more a question of "if we have real cores with separate L1's but
> shared L2's, go with those first, before we start distributing it out
> to separate L2's".

Yes, this is exactly what I meant before. We basically want to avoid
unnecessary, high-volume probe traffic over the L3 or memory controller,
if possible.

So, trying harder to select an L2 sibling would be more beneficial,
IMHO, instead of scanning the whole node.

-- 
Regards/Gruss,
    Boris.