linux-kernel - Re: VolanoMark regression with 2.6.27-rc1

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Message-ID: <20080804052228.GA5444@linux.vnet.ibm.com>
Date:	Mon, 4 Aug 2008 10:52:28 +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@...ux.vnet.ibm.com>,
	Aneesh Kumar KV <aneesh.kumar@...ux.vnet.ibm.com>,
	Balbir Singh <balbir@...ibm.com>
Subject: Re: VolanoMark regression with 2.6.27-rc1

On Mon, Aug 04, 2008 at 01:04:38PM +0800, Zhang, Yanmin wrote:
> 
> On Fri, 2008-08-01 at 10:44 +0530, Dhaval Giani wrote:
> > On Fri, Aug 01, 2008 at 08:39:14AM +0800, Zhang, Yanmin wrote:
> > > 
> > > On Thu, 2008-07-31 at 15:49 +0800, Zhang, Yanmin wrote:
> > > > On Thu, 2008-07-31 at 09:39 +0200, Peter Zijlstra wrote:
> > > > > On Thu, 2008-07-31 at 15:31 +0800, Zhang, Yanmin wrote:
> > > > > > On Thu, 2008-07-31 at 11:20 +0800, Zhang, Yanmin wrote:
> > > > > > > Ingo,
> > > > > > > 
> > > > > > Oh, it looks like they are the old issues in 2.6.26-rc1 and the 2 patches were reverted before 2.6.26.
> > > > > > New patches are merged into 2.6.27-rc1, but the issues are still not resolved clearly.
> > > > > > http://www.uwsg.iu.edu/hypermail/linux/kernel/0805.2/1148.html.
> > > > > 
> > > > > The new smp-group stuff doesn't remotely look like what was in .26
> > > > > 
> > > > > Also, on my quad (admittedly smaller than your machines) both volano and
> > > > > sysbench didn't regress anymore - where they clearly did with the code
> > > > > reverted from .26.
> > > > The regression I reported exists on:
> > > > 1) 8-core+HT(totally 16 logical processor) tulsa: 40% regression with volano, 8% with oltp;
> > > > 2) 8-core+HT Montvale Itanium: 9% regression with volano; 8% with oltp;
> > > > 3) 16-core tigerton: %70 with volano, %18 with oltp;
> > > > 4) 8-core stoakley: %15 with oltp, testing failed with volanoMark.
> > > > 
> > > > So the issues are popular on different architectures.
> > > I know kernel needs the features and it might not be a good idea to reject them over and over again.
> > > I will collect more data on tigerton and try to optimize it.
> > 
> > Hi Yanmin,
> > 
> > Would it be possible for you to switch of the group scheduling feature
> > and see if the regression still exists. In all our testing, we did not
> > see a regression. I would like to eliminate it from your testing as
> > well.
> I tested with CONFIG_GROUP_SCHED=n. To test faster, I simplified the benchmark parameter.
> 
> volanoMark:
> kernel				| 	result
> ----------------------------------------------------------
> 2.6.27-rc1_group		|	205901
> ----------------------------------------------------------
> 2.6.27-rc1_nogroup		|	303377
> ----------------------------------------------------------
> 2.6.26_group			|	529388
> 

There seem to be two different regressions here. One in the user group
scheduling (which I do remember did have problems) and something totally
unrelated to group scheduling. In some of the runs I tried here, I got
similar results for 2.6.27-rc1_nogroup and 2.6.27-rc1_cgroup but had bad
results for user. Anyway, we will need to fix both the regressions.
Would it be possible for you to see what causes the regression between
2.6.26 and 2.6.27-rc1 for the non group scheduling case?

thanks,
-- 
regards,
Dhaval
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