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

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Message-ID: <20130205145854.GA30949@gmail.com>
Date:	Tue, 5 Feb 2013 15:58:54 +0100
From:	Ingo Molnar <mingo@...nel.org>
To:	Alex Shi <alex.shi@...el.com>
Cc:	torvalds@...ux-foundation.org, paul.gortmaker@...driver.com,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] rwsem: steal writing sem for better performance


* 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?

Thanks,

	Ingo
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