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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Date:	Fri, 14 Sep 2012 23:45:32 +0200
From:	Borislav Petkov <bp@...en8.de>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	Nikolay Ulyanitsky <lystor@...il.com>,
	Mike Galbraith <efault@....de>, linux-kernel@...r.kernel.org,
	Andreas Herrmann <andreas.herrmann3@....com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...nel.org>
Subject: Re: 20% performance drop on PostgreSQL 9.2 from kernel 3.5.3 to
 3.6-rc5 on AMD chipsets - bisected

On Fri, Sep 14, 2012 at 11:40:43PM +0200, Peter Zijlstra wrote:
> Hmm, cute. What kind of machine did you test it on? Nikolay's machines
> look to be smallish AMD X6 or ancient Intel c2d (the patch will indeed
> have absolutely no effect on a dual core).

Yep, I took an X6 too. So it's a single-socket, 6-core AMD, F10h.

> I'll see about running pgbench on a bigger Intel tomorrow if Mike
> doesn't beat me to it.

Can try that too on one of the bigger machines I have, if needed.

> The problem the patch is trying to address is not having to scan an
> entire package for idle cores on every wakeup now that packages are
> getting stupid big.
> 
> Regressing Postgres otoh isn't nice either..
> 
> Anyway, I guess I'm fine with nixing this patch until we figure out
> something smarter..
> 
> I'm also curious to know wth postgres does that this patch makes such a
> big difference...

I'm using 9.1 in Debian testing while Nikolay is using 9.2.

Thanks.

-- 
Regards/Gruss,
    Boris.
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