From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760030Ab2JLSER (ORCPT ); Fri, 12 Oct 2012 14:04:17 -0400 Received: from mail.skyhub.de ([78.46.96.112]:42283 "EHLO mail.skyhub.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759921Ab2JLSEP (ORCPT ); Fri, 12 Oct 2012 14:04:15 -0400 Date: Fri, 12 Oct 2012 20:04:11 +0200 From: Borislav Petkov To: "Ma, Ling" Cc: Konrad Rzeszutek Wilk , "mingo@elte.hu" , "hpa@zytor.com" , "tglx@linutronix.de" , "linux-kernel@vger.kernel.org" , "iant@google.com" Subject: Re: [PATCH RFC 2/2] [x86] Optimize copy_page by re-arranging instruction sequence and saving register Message-ID: <20121012180411.GA26245@liondog.tnic> Mail-Followup-To: Borislav Petkov , "Ma, Ling" , Konrad Rzeszutek Wilk , "mingo@elte.hu" , "hpa@zytor.com" , "tglx@linutronix.de" , "linux-kernel@vger.kernel.org" , "iant@google.com" References: <1349958548-1868-1-git-send-email-ling.ma@intel.com> <20121011143527.GA2408@localhost.localdomain> <20121012061813.GC9881@liondog.tnic> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Oct 12, 2012 at 09:07:43AM +0000, Ma, Ling wrote: > > > > So is that also true for AMD CPUs? > > > Although Bulldozer put 32byte instruction into decoupled 16byte entry > > > buffers, it still decode 4 instructions per cycle, so 4 instructions > > > will be fed into execution unit and > > > 2 loads ,1 write will be issued per cycle. > > > > I'd be very interested with what benchmarks are you seeing that perf > > improvement on Atom and who knows, maybe I could find time to run them > > on Bulldozer and see how your patch behaves there :-).M > I use another benchmark from gcc, there are many code, and extract > one simple benchmark, you may use it to test (cc -o copy_page > copy_page.c), my initial result shows new copy page version is still > better on bulldozer machine, because the machine is first release, > please verify result. And CC to Ian. Right, so benchmark shows around 20% speedup on Bulldozer but this is a microbenchmark and before pursue this further, we need to verify whether this brings any palpable speedup with a real benchmark, I don't know, kernbench, netbench, whatever. Even something as boring as kernel build. And probably check for perf regressions on the rest of the uarches. Thanks. -- Regards/Gruss, Boris.