From mboxrd@z Thu Jan 1 00:00:00 1970 From: Neil Horman Subject: Re: [PATCH] x86: Run checksumming in parallel accross multiple alu's Date: Fri, 1 Nov 2013 13:37:01 -0400 Message-ID: <20131101173701.GC8467@hmsreliant.think-freely.org> References: <201310300525.r9U5Pdqo014902@ib.usersys.redhat.com> <20131030110214.GA10220@localhost.localdomain> <52710B09.6090302@redhat.com> <20131031183003.GC25894@hmsreliant.think-freely.org> <1383320566.1737.0.camel@bwh-desktop.uk.level5networks.com> <20131101160802.GB8467@hmsreliant.think-freely.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Ben Hutchings , Doug Ledford , Ingo Molnar , Eric Dumazet , linux-kernel@vger.kernel.org, netdev@vger.kernel.org To: David Laight Return-path: Received: from charlotte.tuxdriver.com ([70.61.120.58]:54515 "EHLO smtp.tuxdriver.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752135Ab3KARhW (ORCPT ); Fri, 1 Nov 2013 13:37:22 -0400 Content-Disposition: inline In-Reply-To: Sender: netdev-owner@vger.kernel.org List-ID: On Fri, Nov 01, 2013 at 04:18:50PM -0000, David Laight wrote: > > How would you suggest replacing the jumps in this case? I agree it would be > > faster here, but I'm not sure how I would implement an increment using a single > > conditional move. > > I think you need 3 instructions, move a 0, conditionally move a 1 > then add. I suspect it won't be a win! > > If you do 'win' it is probably very dependent on how the instructions > get scheduled onto the execution units - which will probably make > it very cpu type dependant. > > David > I agree, that sounds interesting, but very cpu dependent. Thanks for the suggestion, Ben, but I think it would be better if we just did the prefetch here and re-addressed this area when AVX (or addcx/addox) instructions were available for testing on hardware. Neil