From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754766AbXLKQj0 (ORCPT ); Tue, 11 Dec 2007 11:39:26 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751466AbXLKQjR (ORCPT ); Tue, 11 Dec 2007 11:39:17 -0500 Received: from ccs17.jlab.org ([129.57.35.82]:63981 "EHLO ccs17.jlab.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751511AbXLKQjQ (ORCPT ); Tue, 11 Dec 2007 11:39:16 -0500 Message-ID: <475EBD30.1010506@jlab.org> Date: Tue, 11 Dec 2007 11:39:12 -0500 From: Jie Chen Organization: Jefferson Lab User-Agent: Thunderbird 2.0.0.9 (X11/20071031) MIME-Version: 1.0 To: Ingo Molnar CC: linux-kernel@vger.kernel.org, Peter Zijlstra Subject: Re: Possible bug from kernel 2.6.22 and above, 2.6.24-rc4 References: <20071205204645.GC25694@elte.hu> <47570F83.6040601@jlab.org> <20071205210222.GA30089@elte.hu> <47572353.4040606@jlab.org> <20071206104318.GB30838@elte.hu> <47582367.6060602@jlab.org> <20071210105943.GA5370@elte.hu> <475D9BB5.20808@jlab.org> <20071211105149.GA24250@elte.hu> <475EAC81.1020408@jlab.org> <20071211155226.GA1056@elte.hu> In-Reply-To: <20071211155226.GA1056@elte.hu> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Ingo Molnar wrote: > * Jie Chen wrote: > >> Hi, Ingo: >> >> I guess it is a good news. I did patch 2.6.21.7 kernel using your cfs >> patch. The results of pthread_sync is the same as the non-patched >> 2.6.21 kernel. This means the performance of is not related to the >> scheduler. As for overhead of the gettimeofday, there is no difference >> between 2.6.21 and 2.6.24-rc4. The reference time is around 10.5 us >> for both kernel. > > could you please paste again the relevant portion of the output you get > on a "good" .21 kernel versus the output you get on a "bad" .24 kernel? > >> So what is changed between 2.6.21 and 2.6.22? Any hints :-). Thank you >> very much for all your help. > > we'll figure it out i'm sure :) > > Ingo Hi, Ingo: The following is pthread_sync output for 2.6.21.7-cfs-v24 #1 SMP kernel. 2 threads: Computing reference time 1 Sample_size Average Min Max S.D. Outliers 20 10.489085 10.488800 10.491100 0.000539 1 Reference_time_1 = 10.489085 microseconds +/- 0.001057 Computing PARALLEL time Sample_size Average Min Max S.D. Outliers 20 11.106580 11.105650 11.109700 0.001255 0 PARALLEL time = 11.106580 microseconds +/- 0.002460 PARALLEL overhead = 0.617590 microseconds +/- 0.003409 8 threads: Computing reference time 1 Sample_size Average Min Max S.D. Outliers 20 10.488735 10.488500 10.490700 0.000484 1 Reference_time_1 = 10.488735 microseconds +/- 0.000948 Computing PARALLEL time Sample_size Average Min Max S.D. Outliers 20 13.000647 12.991050 13.052700 0.012592 1 PARALLEL time = 13.000647 microseconds +/- 0.024680 PARALLEL overhead = 2.511907 microseconds +/- 0.025594 Output for Kernel 2.6.24-rc4 #1 SMP 2 threads: Computing reference time 1 Sample_size Average Min Max S.D. Outliers 20 10.510535 10.508600 10.518200 0.002237 1 Reference_time_1 = 10.510535 microseconds +/- 0.004384 Computing PARALLEL time Sample_size Average Min Max S.D. Outliers 20 19.668450 19.650200 19.679650 0.008052 0 PARALLEL time = 19.668450 microseconds +/- 0.015782 PARALLEL overhead = 9.157945 microseconds +/- 0.018217 8 threads: Computing reference time 1 Sample_size Average Min Max S.D. Outliers 20 10.491285 10.490100 10.494900 0.001085 1 Reference_time_1 = 10.491285 microseconds +/- 0.002127 Computing PARALLEL time Sample_size Average Min Max S.D. Outliers 20 13.090080 13.079150 13.131450 0.010995 1 PARALLEL time = 13.090080 microseconds +/- 0.021550 PARALLEL overhead = 2.598590 microseconds +/- 0.024534 For 8 threads, both kernels have the similar performance number. But for 2 threads, the 2.6.21 is much better than 2.6.24-rc4. Thank you. -- ############################################### Jie Chen Scientific Computing Group Thomas Jefferson National Accelerator Facility 12000, Jefferson Ave. Newport News, VA 23606 (757)269-5046 (office) (757)269-6248 (fax) chen@jlab.org ###############################################