linux-kernel - Re: [patch] Re: PostgreSQL pgbench performance regression in 2.6.23+

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Message-Id: <1212861381.4953.8.camel@marge.simson.net>
Date:	Sat, 07 Jun 2008 19:56:21 +0200
From:	Mike Galbraith <efault@....de>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Ingo Molnar <mingo@...e.hu>, Greg Smith <gsmith@...gsmith.com>,
	Dhaval Giani <dhaval@...ux.vnet.ibm.com>,
	lkml <linux-kernel@...r.kernel.org>,
	Srivatsa Vaddagiri <vatsa@...ux.vnet.ibm.com>
Subject: Re: [patch] Re: PostgreSQL pgbench performance regression in
	2.6.23+


On Sat, 2008-06-07 at 18:16 +0200, Peter Zijlstra wrote:

> The idea was to dynamically detect sync wakeups, who's defining property
> is that the waker will sleep after waking the wakee. And who's effect is
> pulling tasks together on wakeups - so that we might have the most
> benefit of cache sharing.
> 
> So if we were to exclude cross cpu wakeups from this measurement we'd
> handicap the whole scheme, because then we'd never measure that its
> actually a sync wakeup and wants to run on the same cpu.

Ah, I get it now, thanks.

	-Mike

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