Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753509AbXLEUwb (ORCPT ); Wed, 5 Dec 2007 15:52:31 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751880AbXLEUwY (ORCPT ); Wed, 5 Dec 2007 15:52:24 -0500 Received: from ccs17.jlab.org ([129.57.35.82]:46273 "EHLO ccs17.jlab.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751270AbXLEUwX (ORCPT ); Wed, 5 Dec 2007 15:52:23 -0500 Message-ID: <47570F83.6040601@jlab.org> Date: Wed, 05 Dec 2007 15:52:19 -0500 From: Jie Chen Organization: Jefferson Lab User-Agent: Thunderbird 2.0.0.9 (X11/20071031) MIME-Version: 1.0 To: Ingo Molnar CC: Simon Holm Th??gersen , Eric Dumazet , linux-kernel@vger.kernel.org, Peter Zijlstra Subject: Re: Possible bug from kernel 2.6.22 and above, 2.6.24-rc4 References: <1195698770.11808.4.camel@odie.local> <4744F042.4070002@jlab.org> <20071204131707.GA4232@elte.hu> <4756C3D9.9030107@jlab.org> <20071205154014.GA6491@elte.hu> <4756D058.1070500@jlab.org> <20071205164723.GA25641@elte.hu> <4756E44E.8080607@jlab.org> <20071205200343.GA14570@elte.hu> <475708A7.4030708@jlab.org> <20071205204645.GC25694@elte.hu> In-Reply-To: <20071205204645.GC25694@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 Content-Length: 1712 Lines: 48 Ingo Molnar wrote: > * Jie Chen wrote: > >> I just disabled the affinity mask and reran the test. There were no >> significant changes for two threads (barrier overhead is around 9 >> microseconds). As for 8 threads, the barrier overhead actually drops a >> little, which is good. Let me know whether I can be any help. Thank >> you very much. > > sorry to be dense, but could you give me instructions how i could remove > the affinity mask and test the "barrier overhead" myself? I have built > "pthread_sync" and it outputs numbers for me - which one would be the > barrier overhead: Reference_time_1 ? > > Ingo Hi, Ingo: To disable affinity, do configure --enable-public-release --disable-thread_affinity. You should see barrier overhead like the following: Computing BARRIER time Sample_size Average Min Max S.D. Outliers 20 19.486162 19.482250 19.491400 0.002740 0 BARRIER time = 19.486162 microseconds +/- 0.005371 BARRIER overhead = 8.996257 microseconds +/- 0.006575 The Reference_time_1 is the elapsed time for single thread doing simple loop without any synchronization. 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 ############################################### -- 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/