Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965823AbWKED4P (ORCPT ); Sat, 4 Nov 2006 22:56:15 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S965821AbWKED4P (ORCPT ); Sat, 4 Nov 2006 22:56:15 -0500 Received: from kanga.kvack.org ([66.96.29.28]:39049 "EHLO kanga.kvack.org") by vger.kernel.org with ESMTP id S965823AbWKED4O (ORCPT ); Sat, 4 Nov 2006 22:56:14 -0500 Date: Sat, 4 Nov 2006 22:55:56 -0500 From: Benjamin LaHaise To: Zachary Amsden Cc: Chuck Ebbert <76306.1226@compuserve.com>, Linus Torvalds , Andi Kleen , linux-kernel Subject: Re: [rfc patch] i386: don't save eflags on task switch Message-ID: <20061105035556.GQ9057@kvack.org> References: <200611040200_MC3-1-D04D-6EA3@compuserve.com> <454CE576.3000709@vmware.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <454CE576.3000709@vmware.com> User-Agent: Mutt/1.4.1i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 834 Lines: 19 On Sat, Nov 04, 2006 at 11:09:42AM -0800, Zachary Amsden wrote: > Every processor I've ever measured it on, popf is slower. On P4, for > example, pushf is 6 cycles, and popf is 54. On Opteron, it is 2 / 12. > On Xeon, it is 7 / 91. pushf has to wait until all flag dependancies can be resolved. On the P4 with >100 instructions in flight, that can take a long time. Popf on the other hand has no dependancies on outstanding instructions as it resets the machine state. -ben -- "Time is of no importance, Mr. President, only life is important." Don't Email: . - 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/