From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030525AbXCLQ0R (ORCPT ); Mon, 12 Mar 2007 12:26:17 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1030584AbXCLQ0Q (ORCPT ); Mon, 12 Mar 2007 12:26:16 -0400 Received: from mail-dub.bigfish.com ([213.199.154.10]:35134 "EHLO mail121-dub-R.bigfish.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1030525AbXCLQ0P (ORCPT ); Mon, 12 Mar 2007 12:26:15 -0400 X-BigFish: VP X-Server-Uuid: 5FC0E2DF-CD44-48CD-883A-0ED95B391E89 Date: Mon, 12 Mar 2007 17:24:05 +0100 From: "Joerg Roedel" To: "Avi Kivity" cc: discuss@x86-64.org, "Andi Kleen" , linux-kernel@vger.kernel.org Subject: Re: [PATCH 4/4 TRY#3] optimize and simplify get_cycles_sync() Message-ID: <20070312162405.GA21463@amd.com> References: <20070309150825.GA13481@amd.com> <20070309151511.GE13481@amd.com> <45F1A2FB.7040206@argo.co.il> <20070312130245.GE8922@amd.com> <45F57AEB.5030405@argo.co.il> MIME-Version: 1.0 In-Reply-To: <45F57AEB.5030405@argo.co.il> User-Agent: mutt-ng/devel-r804 (Linux) X-OriginalArrivalTime: 12 Mar 2007 16:25:44.0535 (UTC) FILETIME=[157E5670:01C764C3] X-WSS-ID: 69EBA086328788901-01-01 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Mar 12, 2007 at 06:08:11PM +0200, Avi Kivity wrote: > Joerg Roedel wrote: > >On Fri, Mar 09, 2007 at 08:10:03PM +0200, Avi Kivity wrote: > > > >>Joerg Roedel wrote: > >> > >>>From: Joerg Roedel > >>> > >>>This patch simplifies the get_cycles_sync() function by removing > >>>the #ifdefs from it. Further it introduces an optimization for AMD > >>>processors. There the RDTSCP instruction is used instead of CPUID;RDTSC > >>>which is helpfull if the kernel runs as a KVM guest. Running as a guest > >>>makes CPUID very expensive because it causes an intercept of the guest. > >>> > >>> +#define RDTSCP ".byte 0x0f, 0x01, 0xf9" > >>>+ alternative_io_two("cpuid\nrdtsc", > >>>+ "rdtsc", X86_FEATURE_SYNC_RDTSC, > >>>+ ".byte 0x0f, 0x01, 0xf9", X86_FEATURE_RDTSCP, > >>> > >>why not use the RDTSCP macro here? > >> > > > >Does this macro exist? I couldn't found it in the current git tree. And > >the rdtscp macros in msr.h use the plain opcode too. > > > > -ENOCOFFEE? You defined the macro 3 lines above the .byte directive... Yes, lack of coffee, and even worse -EBLINDHACKER :-( -- Joerg Roedel Operating System Research Center AMD Saxony LLC & Co. KG