Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757037Ab1DGWwN (ORCPT ); Thu, 7 Apr 2011 18:52:13 -0400 Received: from one.firstfloor.org ([213.235.205.2]:36622 "EHLO one.firstfloor.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756442Ab1DGWwM (ORCPT ); Thu, 7 Apr 2011 18:52:12 -0400 Date: Fri, 8 Apr 2011 00:52:08 +0200 From: Andi Kleen To: Raghavendra D Prabhu Cc: Linus Torvalds , Andi Kleen , Andy Lutomirski , x86@kernel.org, Thomas Gleixner , Ingo Molnar , linux-kernel@vger.kernel.org Subject: Re: [RFT/PATCH v2 2/6] x86-64: Optimize vread_tsc's barriers Message-ID: <20110407225208.GD21838@one.firstfloor.org> References: <80b43d57d15f7b141799a7634274ee3bfe5a5855.1302137785.git.luto@mit.edu> <20110407164245.GA21838@one.firstfloor.org> <20110407214307.GA6449@Xye> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20110407214307.GA6449@Xye> User-Agent: Mutt/1.4.2.2i Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 654 Lines: 15 > If only one lfence or serializing instruction is to be used, can't we > just use RDTSCP instruction (X86_FEATURE_RDTSCP,available only in >= > i7's and AMD) which both provides TSC as well as an upward serializing RDTSCP is a full synchronization, much heavier and slower than LFENCE (or even two of them) Besides it doesn't exist on older CPUs. -Andi -- ak@linux.intel.com -- Speaking for myself only. -- 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/