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From: Nick Piggin <nickpiggin@yahoo.com.au>
To: Nicholas Miell <nmiell@comcast.net>
Cc: Cyrus Massoumi <cyrusm@gmx.net>, "Molnar, Ingo" <mingo@elte.hu>,
	LKML <linux-kernel@vger.kernel.org>
Subject: Re: Poor PostgreSQL scaling on Linux 2.6.25-rc5 (vs 2.6.22)
Date: Wed, 12 Mar 2008 10:42:43 +1100	[thread overview]
Message-ID: <200803121042.43895.nickpiggin@yahoo.com.au> (raw)
In-Reply-To: <1205277132.12854.19.camel@entropy>

On Wednesday 12 March 2008 10:12, Nicholas Miell wrote:
> On Tue, 2008-03-11 at 22:34 +0100, Cyrus Massoumi wrote:

> Piggin said the following:
> > The problem with MySQL contention means that if the scheduler
> > unluckily chooses to deschedule a lock holder, then you can get
> > idle time building up on other cores and you can get context switch
> > cascades as things all pile up onto this heavily contended lock. As
> > such, it means MySQL is not an ideal candidate for looking at
> > performance behaviour. I discounted the relatively worse scaling of
> > MySQL with 2.6.25-rc (than 2.6.22) as such an effect.
>
> which I interpreted to mean that MySQL performs worse on 2.6.23+ than on
> 2.6.22 but for some reason this doesn't matter.

I didn't try 2.6.23, which I think has bigger problems due to new
CFS code. 2.6.25-rc fixes that, but yes in general I think the MySQL
performance profile is worse on later kernels: while it has a
very slightly higher peak performance, it drops off in performance
more quickly after that peak. I initially wasn't too worried about
it, but seeing as postgresql has a similar problem, I've made the
scheduler developers aware of it.


  reply	other threads:[~2008-03-11 23:43 UTC|newest]

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-03-11  6:49 Nick Piggin
2008-03-11  7:58 ` Ingo Molnar
2008-03-11  8:28   ` Nick Piggin
2008-03-11  9:59     ` Ingo Molnar
2008-03-11 21:07 ` Nicholas Miell
2008-03-11 21:34   ` Cyrus Massoumi
2008-03-11 23:12     ` Nicholas Miell
2008-03-11 23:42       ` Nick Piggin [this message]
2008-03-11 23:47       ` Stephen Hemminger
2008-03-12  9:00       ` Zhang, Yanmin
     [not found] ` <20080311102538.GA30551@elte.hu>
     [not found]   ` <20080311120230.GA5386@elte.hu>
2008-03-12  1:21     ` Nick Piggin
2008-03-12  7:58       ` Peter Zijlstra
2008-03-17  0:44         ` Nick Piggin
2008-03-17  5:16           ` Ray Lee
2008-03-17  5:21             ` Willy Tarreau
2008-03-17  7:19               ` Nick Piggin
2008-03-17  8:26                 ` Willy Tarreau
2008-03-17  8:54                   ` Nick Piggin
2008-03-17  9:28                     ` Peter Zijlstra
2008-03-17  9:56                       ` Nick Piggin
2008-03-17 10:16                       ` Ingo Molnar
2008-03-17  5:34             ` Nick Piggin
2008-03-14 15:42 Xose Vazquez Perez

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