Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030230AbVIVH55 (ORCPT ); Thu, 22 Sep 2005 03:57:57 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1030243AbVIVH55 (ORCPT ); Thu, 22 Sep 2005 03:57:57 -0400 Received: from mailgate2.mysql.com ([213.136.52.47]:44160 "EHLO mailgate.mysql.com") by vger.kernel.org with ESMTP id S1030230AbVIVH5z (ORCPT ); Thu, 22 Sep 2005 03:57:55 -0400 Message-ID: <433264AF.5060800@mysql.com> Date: Thu, 22 Sep 2005 10:00:47 +0200 From: Jonas Oreland User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.7.11) Gecko/20050915 X-Accept-Language: en-us, en MIME-Version: 1.0 To: Ray Bryant CC: Andi Kleen , Daniel Jacobowitz , john stultz , Andrew Morton , lkml , discuss@x86-64.org Subject: Re: [discuss] Re: [PATCH] x86-64: Fix bad assumption that dualcore cpus have synced TSCs References: <1127157404.3455.209.camel@cog.beaverton.ibm.com> <200509211015.09356.raybry@mpdtxmail.amd.com> <20050921150404.GD12810@verdi.suse.de> <200509211046.25555.raybry@mpdtxmail.amd.com> In-Reply-To: <200509211046.25555.raybry@mpdtxmail.amd.com> Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1120 Lines: 33 Ray Bryant wrote: > On Wednesday 21 September 2005 10:04, Andi Kleen wrote: > > >>We handle this, but single socket dual core was special cased because >>I was told previously it should be ok. >> >>-Andi > > > AFAIK there is a processor state bit that enables/disables this behavior. > Apparently some BIOS's are setting this one way for desktop systems and the > other way for servers. If it is thought to be important I can track that > down and see if it can be externally documented. (It may actually be in the > bios and kernel developer guide...) > Hi, This would be very good (for us single socket dual core users) I tried a very small benchmark: clock_gettime(CLOCK_REALTIME): elapsed 7336657 -> 733.665700ns/call clock_gettime(CLOCK_PROCESS_CPUTIME_ID): elapsed 763247 -> 76.324700ns/call It's a factor 10 faster if the TSC were to be in sync. /Jonas - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/