From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754963AbZKLXEN (ORCPT ); Thu, 12 Nov 2009 18:04:13 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755033AbZKLXEG (ORCPT ); Thu, 12 Nov 2009 18:04:06 -0500 Received: from artax.karlin.mff.cuni.cz ([195.113.26.195]:47220 "EHLO artax.karlin.mff.cuni.cz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755049AbZKLXEF (ORCPT ); Thu, 12 Nov 2009 18:04:05 -0500 Date: Thu, 12 Nov 2009 13:16:19 +0100 From: Pavel Machek To: Ingo Molnar Cc: "H. Peter Anvin" , "Ma, Ling" , Ingo Molnar , Thomas Gleixner , linux-kernel Subject: Re: [PATCH RFC] [X86] performance improvement for memcpy_64.S by fast string. Message-ID: <20091112121619.GD1394@ucw.cz> References: <1257500482-16182-1-git-send-email-ling.ma@intel.com> <4AF457E0.4040107@zytor.com> <4AF4784C.5090800@zytor.com> <8FED46E8A9CA574792FC7AACAC38FE7714FCF772C9@PDSMSX501.ccr.corp.intel.com> <4AF7C66C.6000009@zytor.com> <20091109080830.GI453@elte.hu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20091109080830.GI453@elte.hu> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > Ling, if you are interested, could you send a user-space test-app to > this thread that everyone could just compile and run on various older > boxes, to gather a performance profile of hand-coded versus string ops > performance? > > ( And i think we can make a judgement based on cache-hot performance > alone - if then the strings ops will perform comparatively better in > cache-cold scenarios, so the cache-hot numbers would be a conservative > estimate. ) Ugh, really? I'd expect cache-cold performance to be not helped at all (memory bandwidth limit) and you'll get slow down from additional i-cache misses... Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html