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Date: Fri, 13 Apr 2007 08:34:06 -0700
From: "H. Peter Anvin" <hpa@zytor.com>
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To: Keir Fraser <keir@xensource.com>
CC: Andi Kleen <andi@firstfloor.org>, Zachary Amsden <zach@vmware.com>,
       Andrew Morton <akpm@osdl.org>,
       Virtualization Mailing List <virtualization@lists.osdl.org>,
       Chris Wright <chrisw@sous-sol.org>,
       David Rientjes <rientjes@google.com>, Hugh Dickins <hugh@veritas.com>,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 0/4] i386 - pte update optimizations
References: <C2452891.D417%keir@xensource.com>
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Keir Fraser wrote:
> On 13/4/07 13:27, "Andi Kleen" <andi@firstfloor.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.

Note we're talking a UP-only hack.

	-hpa