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

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Date:	Sat, 07 Jun 2008 16:16:19 +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 15:07 +0200, Peter Zijlstra wrote:
> On Sat, 2008-06-07 at 14:50 +0200, Mike Galbraith wrote:
> > Since I tested mysql+oltp and made the dang pdf of the results, I may
> > as well actually attach the thing <does that before continuing...>.
> > 
> > BTW, I have a question wrt avg_overlap.  When a wakeup cause the current
> > task to begin sharing CPU with a freshly awakened task, the current task
> > is tagged.. but the wakee isn't.  How come?  If one is sharing, so is
> > the other.
> 
> avg_overlap is about measuring how long we'll run after waking someone
> else. The other measure, how long our waker shares the cpu with us,
> hasn't proven to be relevant so far.

Yeah wrt relevance, I've been playing with making it mean this and that,
with approx 0 success ;-)  If it's a measure of how long we run after
waking though, don't we need to make sure it's not a cross CPU wakeup?

	-Mike

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