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

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Message-ID: <20080508053431.GB32729@linux.vnet.ibm.com>
Date:	Thu, 8 May 2008 11:04:31 +0530
From:	Dhaval Giani <dhaval@...ux.vnet.ibm.com>
To:	"Zhang, Yanmin" <yanmin_zhang@...ux.intel.com>
Cc:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Ingo Molnar <mingo@...e.hu>,
	LKML <linux-kernel@...r.kernel.org>,
	Srivatsa Vaddagiri <vatsa@...ibm.com>
Subject: Re: volanoMark regression with kernel 2.6.26-rc1

On Thu, May 08, 2008 at 01:20:12PM +0800, Zhang, Yanmin 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?
> With GROUP_SCHED=y.
> 
> I remember a similiar patch was merged into 2.6.25-rc1 and I found the similiar volanoMark
> regression, then you reverted it. Why to add it back to 2.6.26-rc1?
> 

The implementation has been changed extensively. As of now, without
proper load balancing, group scheduling is not yet fully fair, but such a
performance regression is serious, and we need to figure out why the
regression is taking place.

-- 
regards,
Dhaval
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