Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757744AbYGPSyi (ORCPT ); Wed, 16 Jul 2008 14:54:38 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753151AbYGPSyb (ORCPT ); Wed, 16 Jul 2008 14:54:31 -0400 Received: from gw.goop.org ([64.81.55.164]:55492 "EHLO mail.goop.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752487AbYGPSya (ORCPT ); Wed, 16 Jul 2008 14:54:30 -0400 Message-ID: <487E43D9.7080703@goop.org> Date: Wed, 16 Jul 2008 11:54:17 -0700 From: Jeremy Fitzhardinge User-Agent: Thunderbird 2.0.0.14 (X11/20080501) MIME-Version: 1.0 To: Ingo Molnar CC: Linux Kernel Mailing List , "Alex Nixon (Intern)" , Ian Campbell Subject: Large increase in context switch rate X-Enigmail-Version: 0.95.6 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1475 Lines: 35 Hi Ingo, We have Alex Nixon doing some profiling of Xen kernels, comparing current pvops Xen and native with the last "official" Xen kernel 2.6.18.8-xen. One obvious difference is that the kernbench context switch rate is way up, from about 30k to 110k. Also, the user time went up from about 375s to 390s - and that's comparing pvops native to 2.6.18.8-xen (pvops Xen was more or less identical). I wonder if the user time increase is related to the context switch rate, because the actual context switch time itself is accounted to the process, or because of secondary things like cache and tlb misses. Or perhaps the new scheduler accounts for things differently? Anyway, I'm wondering: * is the increased context switch rate expected? * what tunables are there so we can try and make them have comparable context switch rates? This is an issue because the Xen/pvops kernel is showing a fairly large overall performance regression, and the context switches a specifically slow compared to the old Xen kernel, and the high switch rate is presumably compounding the problem. It would be nice to have some knobs to turn to see what the underlying performance characteristics are. Thanks, J -- 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/