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    SubjectRe: sysbench+mysql(oltp, readonly) 30% regression with 2.6.26-rc1
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    On Thu, 2008-05-08 at 17:01 +0800, Zhang, Yanmin wrote:
    > On Thu, 2008-05-08 at 10:00 +0200, Mike Galbraith wrote:
    > > On Thu, 2008-05-08 at 14:35 +0800, Zhang, Yanmin wrote:
    > > > On Wed, 2008-05-07 at 18:26 +0200, Peter Zijlstra wrote:
    > > > > On Wed, 2008-05-07 at 12:55 +0800, Zhang, Yanmin wrote:
    > > > > > Comparing with kernel 2.6.25, sysbench+mysql(oltp, readonly) has many
    > > > > > regression with 2.6.26-rc1.
    > > > > >
    > > > > > 1) 8-core stoakley: 28%;
    > > > > > 2) 16-core tigerton: 20%;
    > > > > > 3) Itanium Montvale: 50%.
    > > > > >
    > > > > > Bisect located below patch.
    > > > > >
    > > > > > 8f1bc385cfbab474db6c27b5af1e439614f3025c is first bad commit
    > > > > > commit 8f1bc385cfbab474db6c27b5af1e439614f3025c
    > > > > > Author: Peter Zijlstra <a.p.zijlstra@chello.nl>
    > > > > > Date: Sat Apr 19 19:45:00 2008 +0200
    > > > > >
    > > > > > sched: fair: weight calculations
    > > > > >
    > > > > > In order to level the hierarchy, we need to calculate load based on the
    > > > > > root view. That is, each task's load is in the same unit.
    > > > > >
    > > > > >
    > > > > >
    > > > > > After I manually reverted the patch against 2.6.26-rc1 while fixing a couple of
    > > > > > conflictions/errors, sysbench oltp regression became less than 3% on 8-core
    > > > > > stoakley.
    > > > >
    > > > > Does this patch help?
    > > > With the patch, oltp testing result is about 50% worse than the one of pure
    > > > 2.6.26-rc1.
    > >
    > > Hm. I was doing some sysbench+postgress(oltp, ro) testing on my little
    > > Q6600 box this morning, and saw a different picture.
    > How many cpu are in the Q6600?

    That's an Intel Quad core (Kentsfield).

    > > In attached pdf, .bkl refers to Linus' BKL patch, .weight is the weight
    > > fix, both are applied to git.today. The script I used is also attached.
    > With my 8-core stoakley (using mysql):
    > 1) 2.6.25:
    > Number of threads: 6
    > read/write requests: 8025024 (66874.53 per sec.)
    > Number of threads: 8
    > read/write requests: 9132816 (76106.14 per sec.)
    > Number of threads: 10
    > read/write requests: 9244998 (77040.75 per sec.)
    > Number of threads: 12
    > read/write requests: 8994174 (74950.36 per sec.)
    > Number of threads: 14
    > read/write requests: 9051322 (75426.54 per sec.)
    > Number of threads: 16
    > read/write requests: 9015412 (75126.93 per sec.)
    >
    > 2) 2.6.26-rc1:
    > Number of threads: 6
    > read/write requests: 5754056 (47949.87 per sec.)
    > Number of threads: 8
    > read/write requests: 6528480 (54403.29 per sec.)
    > Number of threads: 10
    > read/write requests: 6444690 (53705.16 per sec.)
    > Number of threads: 12
    > read/write requests: 6544258 (54534.23 per sec.)
    > Number of threads: 14
    > read/write requests: 6796650 (56637.65 per sec.)
    > Number of threads: 16
    > read/write requests: 6718110 (55983.18 per sec.)
    >
    > 3) 2.6.26-rc1+weight
    > Number of threads: 16
    > read/write requests: 3219076 (26824.22 per sec.)
    >
    > I'm not sure if more cpu could introduce more contention in this test.

    those numbers make me sad :-(

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