Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752573AbZFBSd4 (ORCPT ); Tue, 2 Jun 2009 14:33:56 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750958AbZFBSds (ORCPT ); Tue, 2 Jun 2009 14:33:48 -0400 Received: from acsinet12.oracle.com ([141.146.126.234]:44873 "EHLO acsinet12.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751225AbZFBSds (ORCPT ); Tue, 2 Jun 2009 14:33:48 -0400 Date: Tue, 2 Jun 2009 14:27:42 -0400 From: Chris Mason To: Pekka Enberg Cc: 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 Subject: Re: [benchmark] 1% performance overhead of paravirt_ops on native kernels Message-ID: <20090602182742.GJ3914@think> Mail-Followup-To: Chris Mason , Pekka Enberg , 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> <84144f020906021106l7927e005o6bcd555b8f51b03b@mail.gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <84144f020906021106l7927e005o6bcd555b8f51b03b@mail.gmail.com> User-Agent: Mutt/1.5.18 (2008-05-17) X-Source-IP: abhmt006.oracle.com [141.146.116.15] X-Auth-Type: Internal IP X-CT-RefId: str=0001.0A010202.4A256F22.01F7:SCFSTAT5015188,ss=1,fgs=0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2041 Lines: 45 On Tue, Jun 02, 2009 at 09:06:41PM +0300, Pekka Enberg wrote: > Hi Chris, > > On Tue, Jun 2, 2009 at 6:03 PM, Chris Mason wrote: > >> I find it ridiculous to use the "but it's used" argument to try to > >> force the code into the kernel. ?By this argument you can say the same > >> about crap like ndiswrapper and similarly harmful code. > > > > 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. > > Maybe it's just me but you make it sound like the SLUB regression is > okay. It's not. Well, it is and it isn't. SLUB was implemented with specific workloads in mind. I'd prefer that regressions not get in at all, but sometimes it takes the broad exposure you get from being in mainline to finish things. Sometimes we finish things with rm, but without slub I don't think the issues it was trying to solve would have been discussed at all. > > Unfortunately we're now in a position where we can't just remove SLUB > (it's an improvement over SLAB for NUMA) so we're stuck with two > allocators with third one on its way to the kernel. So yes, it makes a > lot of sense to me to fix CONFIG_PARAVIRT regression before merging > more of the xen stuff in the kernel. It's always easier to fix these > things before they hit the kernel and people start to depend on them. The problem is that people already depend on them ;) If people want to nack xen based on code structure, that's more than fair, I just hope we can keep the discussion around something the xen developers can work toward. Micro benchmarks come and go, we tune as best we can based on the tradeoffs at hand. -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/