Re: [PATCH] rwsem: steal writing sem for better performance

[Alex Shi]

On 02/05/2013 10:58 PM, Ingo Molnar wrote:
> 
> * Alex Shi <alex.shi@xxxxxxxxx> wrote:
> 
>> Commit 5a50508 change to rwsem from mutex, that cause aim7 fork_test
>> dropped 50%. Yuanhan liu does a good analysis, find it caused by
>> strict sequential writing. Ingo suggest stealing sem writing from
>> front task in waiting queue. https://lkml.org/lkml/2013/1/29/84
>> So has this patch.
>>
>> In this patch, I just allow writing steal happen when the 
>> first waiter is also writer. Then the performance fully 
>> recovered.
> 
> All the aim7 fork_test performance regression is recovered?

Sure. 100% recovered on my NHM EP, NHM EX, SNB EP 2S and 4S machines.
> 
> Thanks,
> 
> 	Ingo
> 


-- 
Thanks Alex
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