linux-kernel - Re: [PATCH v4 1/5] rwsem: check the lock before cpmxchg in down_write

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Message-ID: <51CB9631.1030508@intel.com>
Date:	Thu, 27 Jun 2013 09:32:33 +0800
From:	Alex Shi <alex.shi@...el.com>
To:	Tim Chen <tim.c.chen@...ux.intel.com>
CC:	Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Andi Kleen <andi@...stfloor.org>,
	Michel Lespinasse <walken@...gle.com>,
	Davidlohr Bueso <davidlohr.bueso@...com>,
	Matthew R Wilcox <matthew.r.wilcox@...el.com>,
	Dave Hansen <dave.hansen@...el.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Rik van Riel <riel@...hat.com>,
	Peter Hurley <peter@...leysoftware.com>,
	linux-kernel@...r.kernel.org, linux-mm <linux-mm@...ck.org>
Subject: Re: [PATCH v4 1/5] rwsem: check the lock before cpmxchg in down_write_trylock


The following line should be added head of commit log on patches 1~4. :)

From: Alex Shi <alex.shi@...el.com>


> Cmpxchg will cause the cacheline bouning when do the value checking,
> that cause scalability issue in a large machine (like a 80 core box).
> 
> So a lock pre-read can relief this contention.
> 
> Signed-off-by: Alex Shi <alex.shi@...el.com>


-- 
Thanks
    Alex
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