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Date: Fri, 15 Feb 2008 17:25:05 +0800 From: "Zhang, Yanmin" <yanmin_zhang@...ux.intel.com> To: vatsa@...ux.vnet.ibm.com Cc: Balbir Singh <balbir@...ux.vnet.ibm.com>, LKML <linux-kernel@...r.kernel.org>, Ingo Molnar <mingo@...e.hu>, Peter Zijlstra <a.p.zijlstra@...llo.nl> Subject: Re: 2.6.25-rc1: volanoMark 45% regression On Thu, 2008-02-14 at 15:41 +0800, Zhang, Yanmin wrote: > On Wed, 2008-02-13 at 17:37 +0530, Srivatsa Vaddagiri wrote: > > On Wed, Feb 13, 2008 at 03:15:16PM +0530, Balbir Singh wrote: > > > Zhang, Yanmin wrote: > > > > volanoMark has 45% regression with kernel 2.6.25-rc1 on my both 8-core > > > > stoakley and 16-core Tigerton. > > > > > > > > I used bisect to locate below patch. > > > > > > > > commit 58e2d4ca581167c2a079f4ee02be2f0bc52e8729 > > > > Author: Srivatsa Vaddagiri <vatsa@...ux.vnet.ibm.com> > > > > Date: Fri Jan 25 21:08:00 2008 +0100 > > > > > > > > sched: group scheduling, change how cpu load is calculated > > > > > > > > > > > > > > > > hackbench has about 30% regression on 16-core tigerton, but has about 10% improvement > > > > on 8-core stoakley. > > > > > > > > In addition, tbench has about 6% regression on my 8-core stoakley and > > > > 25% regression on 16-core stoakley. > I verified tbench regression is not caused by the same patch. I am digging tbench now. > > > Some other benchmarks, like netperf/aim7 > > > > also have some regression. I will verify if they are all related to the > > > > patch. > > > > > > > > -yanmin > > > > > > Hi, Yamin, > > > > > > Thanks for reporting the issue? Any chance we could getthe Oprofile output for > > > the run? > I got oprofile data but it didn't show clear evidence. > > When doing volanoMark testing, vmstat showed the good kernel's context switch > is about 1100000, but the bad kernel's context switch is 720000. Good kernel's > idle is about 1%, and bad kernel's idle is about 5%. > > > The exact commandline and .config being used would also help. > I used some scripts to start volanoMark. > > Netperf loop UDP-RR-1/512's 10% regression netperf loopback UDP-RR-1/512 regression is 5% on 8-core stoakley and 16-core tigerton. On tulsa machine (8 cores+hyperThread), it's 18%. If set CONFIG_FAIR_GROUP_SCHED=n, part regression of netperf disappears. If I change dst_entry like what I said in http://marc.info/?l=linux-kernel&m=120305556317006&w=2, plus CONFIG_FAIR_GROUP_SCHED=n, the result is a little better than 2.6.24. I have a couple of different machines and sometimes benchmarks might have different behavior. Sorry for the update. > on 16-core tigerton is also related to the patch. > If I set CONFIG_FAIR_GROUP_SCHED=n, there is no the netperf regression. I bind the netserver > process to a core and bind the client to another core in another processor. > > It's hard to debug into netperf regression if it's caused by scheduler. > > > > > Yamin, > > I would also like to know against which previous version is this > > regression being compared with. Is it 2.6.24? > Yes. > > > Did you have > > CONFIG_FAIR_USER_SCHED enabled in both cases? > Yes. > > CONFIG_FAIR_GROUP_SCHED=y > CONFIG_FAIR_USER_SCHED=y > > > It would also help to know if you > > see the same regression with FAIR_GROUP_SCHED turned off. > No regression if CONFIG_FAIR_GROUP_SCHED=n. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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