From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933175Ab2JLNgR (ORCPT ); Fri, 12 Oct 2012 09:36:17 -0400 Received: from one.firstfloor.org ([213.235.205.2]:51345 "EHLO one.firstfloor.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932805Ab2JLNf7 (ORCPT ); Fri, 12 Oct 2012 09:35:59 -0400 Date: Fri, 12 Oct 2012 15:35:54 +0200 From: Andi Kleen To: "Ma, Ling" Cc: Andi Kleen , "mingo@elte.hu" , "hpa@zytor.com" , "tglx@linutronix.de" , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH RFC 2/2] [x86] Optimize copy_page by re-arranging instruction sequence and saving register Message-ID: <20121012133554.GA16230@one.firstfloor.org> References: <1349958548-1868-1-git-send-email-ling.ma@intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.4.2.2i Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > I tested new and original version on core2, the patch improved performance about 9%, That's not useful because core2 doesn't use this variant, it uses the rep string variant. Primary user is P4. > Although core2 is out-of-order pipeline and weaken instruction sequence requirement, > because of ROB size limitation, new patch issues write operation earlier and > get more parallelism possibility for the pair of write and load ops and better result. > Attached core2-cpu-info (I have no older machine) If you can't test the CPUs who run this code I think it's safer if you add a new variant for Atom, not change the existing well tested code. Otherwise you risk performance regressions on these older CPUs. -Andi -- ak@linux.intel.com -- Speaking for myself only.