Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1762752AbZATTug (ORCPT ); Tue, 20 Jan 2009 14:50:36 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755381AbZATTuW (ORCPT ); Tue, 20 Jan 2009 14:50:22 -0500 Received: from casper.infradead.org ([85.118.1.10]:47700 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753277AbZATTuU (ORCPT ); Tue, 20 Jan 2009 14:50:20 -0500 Subject: Re: gcc inlining heuristics was Re: [PATCH -v7][RFC]: mutex: implement adaptive spinning From: David Woodhouse To: Ingo Molnar Cc: Nick Piggin , Linus Torvalds , Bernd Schmidt , Andi Kleen , Andrew Morton , Harvey Harrison , "H. Peter Anvin" , Chris Mason , Peter Zijlstra , Steven Rostedt , paulmck@linux.vnet.ibm.com, Gregory Haskins , Matthew Wilcox , Linux Kernel Mailing List , linux-fsdevel , linux-btrfs , Thomas Gleixner , Peter Morreale , Sven Dietrich , jh@suse.cz In-Reply-To: <20090120123824.GD7790@elte.hu> References: <20090112005228.GS26290@one.firstfloor.org> <496B86B5.3090707@t-online.de> <20090112193201.GA23848@one.firstfloor.org> <496BBE27.2020206@t-online.de> <20090119001345.GA9880@elte.hu> <20090119062212.GC22584@wotan.suse.de> <20090120005124.GD16304@wotan.suse.de> <20090120123824.GD7790@elte.hu> Content-Type: text/plain Date: Wed, 21 Jan 2009 06:49:00 +1100 Message-Id: <1232480940.22233.1435.camel@macbook.infradead.org> Mime-Version: 1.0 X-Mailer: Evolution 2.24.2 (2.24.2-3.fc10) Content-Transfer-Encoding: 7bit X-SRS-Rewrite: SMTP reverse-path rewritten from by casper.infradead.org See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1381 Lines: 32 On Tue, 2009-01-20 at 13:38 +0100, Ingo Molnar wrote: > > * Nick Piggin wrote: > > > > > it seems like a nice opt-in thing that can be used where the aliases > > > > are verified and the code is particularly performance critical... > > > > > > Yes. I think we could use it in the kernel, although I'm not sure how > > > many cases we would ever find where we really care. > > > > Yeah, we don't tend to do a lot of intensive data processing, so it is > > normally the cache misses that hurt most as you noted earlier. > > > > Some places it might be appropriate, though. It might be nice if it can > > bring code size down too... > > I checked, its size effects were miniscule [0.17%] on the x86 defconfig > kernel and it seems to be a clear loss in total cost as there would be an > ongoing maintenance cost They were talking about 'restrict', not strict-aliasing. Where it can be used, it's going to give you optimisations that strict-aliasing can't. -- David Woodhouse Open Source Technology Centre David.Woodhouse@intel.com Intel Corporation -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/