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

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Message-ID: <51119ED0.3030207@intel.com>
Date:	Wed, 06 Feb 2013 08:07:44 +0800
From:	Alex Shi <alex.shi@...el.com>
To:	Ingo Molnar <mingo@...nel.org>
CC:	torvalds@...ux-foundation.org, paul.gortmaker@...driver.com,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] rwsem: steal writing sem for better performance

On 02/05/2013 10:58 PM, Ingo Molnar wrote:
> 
> * Alex Shi <alex.shi@...el.com> 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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