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    SubjectRe: aim7 -30% regression in 2.6.24-rc1
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    On Mon, 2007-10-29 at 17:37 +0800, Zhang, Yanmin wrote:
    > On Mon, 2007-10-29 at 10:22 +0800, Zhang, Yanmin wrote:
    > > On Fri, 2007-10-26 at 13:23 +0200, Ingo Molnar wrote:
    > > > * Zhang, Yanmin <yanmin_zhang@linux.intel.com> wrote:
    > > >
    > > > > I tested 2.6.24-rc1 on my x86_64 machine which has 2 quad-core processors.
    > > > >
    > > > > Comparing with 2.6.23, aim7 has about -30% regression. I did a bisect
    > > > > and found patch
    > > > > http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=b5869ce7f68b233ceb81465a7644be0d9a5f3dbb
    > > > > caused the issue.
    > > >
    > > > weird, that's a commit diff - i.e. it changes no code.
    > > I got the tag from #git log. As for above link, I just added prior http address,
    > > so readers could check the patch by clicking.
    > >
    > > >
    > > > > kbuild/SPECjbb2000/SPECjbb2005 also has big regressions. On my another
    > > > > tigerton machine (4 quad-core processors), SPECjbb2005 has more than
    > > > > -40% regression. I didn't do a bisect on such benchmark testing, but I
    > > > > suspect the root cause is like aim7's.
    > > >
    > > > these two commits might be relevant:
    > > >
    > > > 7a6c6bcee029a978f866511d6e41dbc7301fde4c
    > > I did a quick testing. This patch has no impact.
    > >
    > > > 95dbb421d12fdd9796ed153853daf3679809274f
    > > Above big patch doesn't include this one, which means if I do
    > > 'git checkout b5869ce7f68b233ceb81465a7644be0d9a5f3dbb', the kernel doesn't include
    > > 95dbb421d12fdd9796ed153853daf3679809274f.
    > >
    > > >
    > > > but a bisection result would be the best info.
    > > I will do a bisect between 2.6.23 and tag 9c63d9c021f375a2708ad79043d6f4dd1291a085.
    > I ran git bisect with kernel version as the tag. It looks like git will
    > be crazy sometimes. So I checked ChangeLog and used the number tag to replace
    > the kernel version and retested it.
    >
    > It looks like at least 2 patches were responsible for the regression. I'm
    > doing sub-bisect now.
    >
    > I could find aim7 regression on all my testing machines although the regression
    > percentage is different.
    >
    > Machine regression
    > 8-core stoakley 30%
    > 16-core tigerton 6%
    > tulsa(dual-core+HT, 16 logical cpu) 20%
    sub-bisecting captured patch 38ad464d410dadceda1563f36bdb0be7fe4c8938(sched: uniform tunings)
    caused 20% regression of aim7.

    The last 10% should be also related to sched parameters, such like
    sysctl_sched_min_granularity.

    -yanmin
    -
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