Re: hackbench regression with kernel 2.6.32-rc1

From: Mike Galbraith
Date: Wed Oct 28 2009 - 10:23:09 EST


On Wed, 2009-10-28 at 17:29 +0800, Zhang, Yanmin wrote:
> -Mike
> I'm investigating 5% tbench regression on Nehalem machine. perf_counter shows
> select_task_rq_fair consumes about 5% cpu time with 2.6.32-rc1 while it consumes
> less than 0.5% with 2.6.31.
>
> Patch c88d5910890 has comments to explain it, but I still can't understand why
> to add complicated balance logic when selecting task rq.
>
> I will check which section in function ïselect_task_rq_fair consumes so much time.

Turn off SD_WAKE_BALANCE as it was called in rc1. See commit 182a85f.

-Mike

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