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SubjectRe: -mm seems significanty slower than mainline on kernbench
Peter Williams wrote:
> Martin Bligh wrote:
>
>> Andy Whitcroft wrote:
>>
>>> Andy Whitcroft wrote:
>>>
>>>> Peter Williams wrote:
>>>>
>>>>
>>>>
>>>>> Attached is a new patch to fix the excessive idle problem. This patch
>>>>> takes a new approach to the problem as it was becoming obvious that
>>>>> trying to alter the load balancing code to cope with biased load was
>>>>> harder than it seemed.
>>>>
>>>>
>>>>
>>>>
>>>> Ok. Tried testing different-approach-to-smp-nice-problem against the
>>>> transition release 2.6.14-rc2-mm1 but it doesn't apply. Am testing
>>>> against 2.6.15-mm3 right now. Will let you know.
>>>
>>>
>>>
>>>
>>> Doesn't appear to help if I am analysing the graphs right. Martin?
>>
>>
>>
>> Nope. still broken.
>
>
> Interesting. The only real difference between this and Con's original
> patch is the stuff that he did in source_load() and target_load() to
> nobble the bias when nr_running is 1 or less. With this new model it
> should be possible to do something similar in those functions but I'll
> hold off doing anything until a comparison against 2.6.15-mm3 with the
> patch removed is available (as there are other scheduler changes in -mm3).
>

Ideally, balancing should be completely unaffected when all tasks are
of priority 0 which is what I thought yours did, and why I think the
current system is not great.

I'll probably end up taking a look at it one day, if it doesn't get fixed.
I think your patch is pretty close but I didn't quite look close enough to
work out what's going wrong.

--
SUSE Labs, Novell Inc.

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