linux-kernel - Re: [PATCH 0/4] i386 - pte update optimizations

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Message-ID: <C2452891.D417%keir@xensource.com>
Date:	Fri, 13 Apr 2007 12:31:13 +0100
From:	Keir Fraser <keir@...source.com>
To:	Andi Kleen <andi@...stfloor.org>
CC:	Zachary Amsden <zach@...are.com>, "H. Peter Anvin" <hpa@...or.com>,
	Andrew Morton <akpm@...l.org>,
	Virtualization Mailing List <virtualization@...ts.osdl.org>,
	Chris Wright <chrisw@...s-sol.org>,
	David Rientjes <rientjes@...gle.com>,
	Hugh Dickins <hugh@...itas.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 0/4] i386 - pte update optimizations

On 13/4/07 13:27, "Andi Kleen" <andi@...stfloor.org> wrote:

>> LOCKed instruction suck really badly on the netburst microarchitecture (like
>> factor of 10x, or not far off). I think it's probably because of their side
>> effect of serialising memory accesses, causing horrible pipeline stalls.
> 
> Unfortunately they tend to be HyperThreaded usually (except for early ones
> and Celerons) and need the LOCK anyways.

Fair point, although quite a few people disable HT.

 -- Keir

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