Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932320AbWCMTYe (ORCPT ); Mon, 13 Mar 2006 14:24:34 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932296AbWCMTYe (ORCPT ); Mon, 13 Mar 2006 14:24:34 -0500 Received: from mx.pathscale.com ([64.160.42.68]:50892 "EHLO mx.pathscale.com") by vger.kernel.org with ESMTP id S932320AbWCMTYd (ORCPT ); Mon, 13 Mar 2006 14:24:33 -0500 Subject: Re: [PATCH 18 of 20] ipath - kbuild infrastructure From: "Bryan O'Sullivan" To: Adrian Bunk Cc: rjwalsh@pathscale.com, rolandd@cisco.com, gregkh@suse.de, akpm@osdl.org, davem@davemloft.net, linux-kernel@vger.kernel.org, openib-general@openib.org In-Reply-To: <20060313181025.GA13973@stusta.de> References: <867a396dd518ac63ab41.1141950948@eng-12.pathscale.com> <20060313181025.GA13973@stusta.de> Content-Type: text/plain Organization: PathScale, Inc. Date: Mon, 13 Mar 2006 11:24:28 -0800 Message-Id: <1142277868.9032.14.camel@serpentine.pathscale.com> Mime-Version: 1.0 X-Mailer: Evolution 2.2.3 (2.2.3-2.fc4) Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1354 Lines: 37 On Mon, 2006-03-13 at 19:10 +0100, Adrian Bunk wrote: > I'm still a bit surprised, since in the rest of the kernel we are even > going from -O2 to -Os for getting better performance. > > Robert said he wanted to post some numbers showing that -O3 is > measurably better for you [1], but I haven't seen them. I just ran some numbers. At large packet sizes, it doesn't matter what options we use, because we spend all of our time in __iowrite_copy32, which uses the string copy instructions. For small packets, my quick tests indicate that -Os gives about 5% *better* performance than -O3 (using gcc 4 on FC4). This is in line with what people have been finding in the kernel in general recently. So if I change that CFLAGS line from -O3 to -Os, are we in OK shape? :-) > > +_ipath_idstr:="PathScale $(shell date +%F)" > > +EXTRA_CFLAGS += -DIPATH_IDSTR='$(_ipath_idstr)' -DIPATH_KERN_TYPE=0 > >... > > UTS_VERSION is already available and printed at the top of dmesg. > I don't see the point in printing it a second time. Good point. The idstr stuff is for our out-of-tree drivers. Thanks,