From mboxrd@z Thu Jan 1 00:00:00 1970 From: "H. Peter Anvin" Subject: Re: [PATCH 0/4] i386 - pte update optimizations Date: Fri, 13 Apr 2007 08:34:06 -0700 Message-ID: <461FA2EE.5090103@zytor.com> References: Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Return-path: In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: virtualization-bounces@lists.linux-foundation.org Errors-To: virtualization-bounces@lists.linux-foundation.org To: Keir Fraser Cc: Andrew Morton , Andi Kleen , Chris Wright , David Rientjes , Virtualization Mailing List , Hugh Dickins , Linux Kernel Mailing List List-Id: virtualization@lists.linuxfoundation.org Keir Fraser wrote: > On 13/4/07 13:27, "Andi Kleen" 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 on= es >> 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