From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1161000AbXCGAZy (ORCPT ); Tue, 6 Mar 2007 19:25:54 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1161001AbXCGAZy (ORCPT ); Tue, 6 Mar 2007 19:25:54 -0500 Received: from smtp.osdl.org ([65.172.181.24]:38829 "EHLO smtp.osdl.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1161000AbXCGAZx (ORCPT ); Tue, 6 Mar 2007 19:25:53 -0500 Date: Tue, 6 Mar 2007 16:25:41 -0800 From: Andrew Morton To: "Joerg Roedel" Cc: discuss@x86-64.org, "Andi Kleen" , linux-kernel@vger.kernel.org Subject: Re: [PATCH 4/4] optimize and simplify get_cycles_sync() Message-Id: <20070306162541.2b8a148d.akpm@linux-foundation.org> In-Reply-To: <20070228142554.GE19452@amd.com> References: <20070228140501.GA19452@amd.com> <20070228142554.GE19452@amd.com> X-Mailer: Sylpheed version 2.2.7 (GTK+ 2.8.6; i686-pc-linux-gnu) Mime-Version: 1.0 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 On Wed, 28 Feb 2007 15:25:54 +0100 "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. Problem: http://test.kernel.org/functional/index.html lots of builds fell over because their binutils versions don't understand rdtscp. I don't know how recently rdtscp support was added to binutils, but this is likely to be a problem. Perhaps we can change this patch to embed the hex code for that opcode instead?