Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1762859AbXJDQQv (ORCPT ); Thu, 4 Oct 2007 12:16:51 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1762577AbXJDQQZ (ORCPT ); Thu, 4 Oct 2007 12:16:25 -0400 Received: from palinux.external.hp.com ([192.25.206.14]:57708 "EHLO mail.parisc-linux.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758716AbXJDQQX (ORCPT ); Thu, 4 Oct 2007 12:16:23 -0400 Date: Thu, 4 Oct 2007 10:16:21 -0600 From: Matthew Wilcox To: Christoph Lameter Cc: Nick Piggin , Christoph Hellwig , Mel Gorman , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, David Chinner , Jens Axboe Subject: SLUB performance regression vs SLAB Message-ID: <20071004161621.GO12049@parisc-linux.org> References: <20070919033605.785839297@sgi.com> <200709280742.38262.nickpiggin@yahoo.com.au> <200709281514.48293.nickpiggin@yahoo.com.au> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.13 (2006-08-11) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2719 Lines: 51 On Mon, Oct 01, 2007 at 01:50:44PM -0700, Christoph Lameter wrote: > The problem is with the weird way of Intel testing and communication. > Every 3-6 month or so they will tell you the system is X% up or down on > arch Y (and they wont give you details because its somehow secret). And > then there are conflicting statements by the two or so performance test > departments. One of them repeatedly assured me that they do not see any > regressions. Could you cut out the snarky remarks? It takes a long time to run a test, and testing every one of the patches you send really isn't high on anyone's priority list. The performance team have also been having problems getting stable results with recent kernels, adding to the delay. The good news is that we do now have committment to testing upstream kernels, so you should see results more frequently than you have been. I'm taking over from Suresh as liason for the performance team, so if you hear *anything* from *anyone* else at Intel about performance, I want you to cc me about it. OK? And I don't want to hear any more whining about hearing different things from different people. So, on "a well-known OLTP benchmark which prohibits publishing absolute numbers" and on an x86-64 system (I don't think exactly which model is important), we're seeing *6.51%* performance loss on slub vs slab. This is with a 2.6.23-rc3 kernel. Tuning the boot parameters, as you've asked for before (slub_min_order=2, slub_max_order=4, slub_min_objects=8) gets back 0.38% of that. It's still down 6.13% over slab. For what it's worth, 2.6.23-rc3 already has a 1.19% regression versus RHEL 4.5, so the performance guys are really unhappy about going up to almost 8% regression. In the detailed profiles, __slab_free is the third most expensive function, behind only spin locks. get_partial_node is right behind it in fourth place, and kmem_cache_alloc is sixth. __slab_alloc is eight and kmem_cache_free is tenth. These positions don't change with the slub boot parameters. Now, where do we go next? I suspect that 2.6.23-rc9 has significant changes since -rc3, but I'd like to confirm that before kicking off another (expensive) run. Please, tell me what useful kernels are to test. -- Intel are signing my paycheques ... these opinions are still mine "Bill, look, we understand that you're interested in selling us this operating system, but compare it to ours. We can't possibly take such a retrograde step." - 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/