Re: -mm seems significanty slower than mainline on kernbench

[Nick Piggin <nickpiggin@yahoo.com.au>]

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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