Performance regression of specjbb2005/aim7 with 2.6.29-rc1

[Zhang, Yanmin]

Comparing with 2.6.28's results, specjbb2005 has about 7% regression with 2.6.29-rc1
on my a couple of x86_64 machines. aim7 has about 1.7% regression.

Ming did a quick bisect with aim7 and located below patch.

ïcommit 0a582440ff546e2c6610d1acec325e91b4efd313
Author: Mike Galbraith <efault@xxxxxx>
Date:   Fri Jan 2 12:16:42 2009 +0100

    sched: fix sched_slice()
    
    Impact: fix bad-interactivity buglet
    
    Fix sched_slice() to emit a sane result whether a task is currently
    enqueued or not.
    
    Signed-off-by: Mike Galbraith <efault@xxxxxx>
    Tested-by: Jayson King <dev@xxxxxxxxxxxxxx>
    Signed-off-by: Ingo Molnar <mingo@xxxxxxx>


After we revert the patch, aim7 regression disappeared. specjbb2005 regression becomes
less than 1.5% on 8-core stokley and disappears on 16-core tigerton. I don't know what
causes the last 1.5% regression.

As tbench has about 5% improvement and oltp(mysql+sysbench) has 5% improvement, we also tested
to make sure such improvement isn't related to above patch. volanoMark's improvement is also not
related to the patch. So it seems safe to revert it.

yanmin



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