linux-kernel - Re: volanoMark regression with kernel 2.6.26-rc1

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Date:	Thu, 08 May 2008 14:07:30 +0800
From:	"Zhang, Yanmin" <yanmin_zhang@...ux.intel.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Ingo Molnar <mingo@...e.hu>, LKML <linux-kernel@...r.kernel.org>,
	Dhaval Giani <dhaval@...ux.vnet.ibm.com>,
	Srivatsa Vaddagiri <vatsa@...ibm.com>
Subject: Re: volanoMark regression with kernel 2.6.26-rc1


On Wed, 2008-05-07 at 20:58 +0200, Peter Zijlstra wrote:
> On Wed, 2008-05-07 at 19:34 +0200, Peter Zijlstra wrote:
> > On Wed, 2008-05-07 at 11:17 +0200, Ingo Molnar wrote:
> > > * Zhang, Yanmin <yanmin_zhang@...ux.intel.com> wrote:
> > > 
> > > > Comparing with 2.6.25, volanoMark has big regression with kernel 
> > > > 2.6.26-rc1. It's about 50% on my 8-core stoakley, 16-core tigerton, 
> > > > and Itanium Montecito.
> > > > 
> > > > With bisect, I located below patch.
> > > 
> > > thanks Yanmin, i've queued up your patch that reverts this change.
> > 
> > Is this really needed now that GROUP_SCHED defaults to 'n' ?
> > 
> > Yanmin, this is with GROUP_SCHED=y, right or is this without?
> 
> Its a long shot, but does the below help?
I tested it on 8-core stoakley. The result is equal to the one of pure 2.6.26-rc1.

> 
> ---
> Subject: sched: fixup SMP load-balance 
> 
> Keeping the aggregate on the first cpu of the sched domain has two problems:
>  - it could collide between different sched domains on different cpus
>  - it could slow things down because of the remote accesses
> 
> Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
> ---
>  include/linux/sched.h |    1 
>  kernel/sched.c        |  113 +++++++++++++++++++++++---------------------------
>  kernel/sched_fair.c   |   12 ++---
>  3 files changed, 60 insertions(+), 66 deletions(-)


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