Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755719AbZFBQ1S (ORCPT ); Tue, 2 Jun 2009 12:27:18 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753117AbZFBQ1I (ORCPT ); Tue, 2 Jun 2009 12:27:08 -0400 Received: from acsinet11.oracle.com ([141.146.126.233]:45713 "EHLO acsinet11.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753037AbZFBQ1H (ORCPT ); Tue, 2 Jun 2009 12:27:07 -0400 Date: Tue, 2 Jun 2009 12:20:08 -0400 From: Chris Mason To: Ulrich Drepper Cc: Ingo Molnar , Nick Piggin , Jeremy Fitzhardinge , "H. Peter Anvin" , Thomas Gleixner , Linux Kernel Mailing List , Andrew Morton , Linus Torvalds , Peter Zijlstra , Avi Kivity , Arjan van de Ven Subject: Re: [benchmark] 1% performance overhead of paravirt_ops on native kernels Message-ID: <20090602162008.GH3914@think> Mail-Followup-To: Chris Mason , Ulrich Drepper , Ingo Molnar , Nick Piggin , Jeremy Fitzhardinge , "H. Peter Anvin" , Thomas Gleixner , Linux Kernel Mailing List , Andrew Morton , Linus Torvalds , Peter Zijlstra , Avi Kivity , Arjan van de Ven References: <4A0B62F7.5030802@goop.org> <20090525091527.GA7535@elte.hu> <4A1C3805.7060404@goop.org> <20090528061702.GB6920@wotan.suse.de> <20090530102330.GC16913@elte.hu> <20090602141802.GC3914@think> <20090602150339.GF3914@think> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.5.18 (2008-05-17) X-Source-IP: abhmt004.oracle.com [141.146.116.13] X-Auth-Type: Internal IP X-CT-RefId: str=0001.0A090203.4A25513E.023D:SCFSTAT5015188,ss=1,fgs=0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1558 Lines: 42 On Tue, Jun 02, 2009 at 08:22:57AM -0700, Ulrich Drepper wrote: > On Tue, Jun 2, 2009 at 8:03 AM, Chris Mason wrote: > > The idea that people shipping xen aren't interested in performance > > regressions is really strange to me. > > Why? They have a different base line. For them any regression to > bare hardware performance is even a positive (since it means the gap > between hardware and virt shrinks). And we would have gotten away with it too if it weren't for you meddling kids! > > > > Dynamic patching is a big wad of duct tape over the problem. > > And what do you call the Xen model? It's a perfect fit IMO. > > > I'm not saying to take harmful code, I'm saying to take code with a > > small performance regression under a specific CONFIG_. ?Slub regresses > > more than 1% on database loads, CONFIG_SCHED_GROUPS, the list goes on > > and on. > > None of those have to be enabled in default kernels. > > > > The best place to fix xen is in the kernel. > > No. The best way to fix things is _on the way into the kernel_. It all depends on which parts are causing problems. A 1% performance hit, under a CONFIG_ that can be disabled? If maintainers are focusing on details like this for long term and active projects, we're doing something very wrong. -chris -- 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/