From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753893AbXLKWLc (ORCPT ); Tue, 11 Dec 2007 17:11:32 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751232AbXLKWLX (ORCPT ); Tue, 11 Dec 2007 17:11:23 -0500 Received: from ccs17.jlab.org ([129.57.35.82]:46039 "EHLO ccs17.jlab.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751036AbXLKWLX (ORCPT ); Tue, 11 Dec 2007 17:11:23 -0500 Message-ID: <475F0B07.2060303@jlab.org> Date: Tue, 11 Dec 2007 17:11:19 -0500 From: Jie Chen Organization: Jefferson Lab User-Agent: Thunderbird 2.0.0.0 (X11/20070419) 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: <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> <475EBD30.1010506@jlab.org> <20071211212352.GF6902@elte.hu> In-Reply-To: <20071211212352.GF6902@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: > >> The following is pthread_sync output for 2.6.21.7-cfs-v24 #1 SMP >> kernel. > >> 2 threads: > >> PARALLEL time = 11.106580 microseconds +/- 0.002460 >> PARALLEL overhead = 0.617590 microseconds +/- 0.003409 > >> Output for Kernel 2.6.24-rc4 #1 SMP > >> PARALLEL time = 19.668450 microseconds +/- 0.015782 >> PARALLEL overhead = 9.157945 microseconds +/- 0.018217 > > ok, so the problem is that this PARALLEL time has an additional +9 usecs > overhead, right? I dont see this myself on a Core2 CPU: > > PARALLEL time = 10.446933 microseconds +/- 0.078849 > PARALLEL overhead = 0.751732 microseconds +/- 0.177446 > > Ingo Hi, Ingo: Yes, the extra 9 usecs overhead for running two threads in the 2.6.24 kernel when there are total of 8 cores (2 quad opterons). What is the total number of cores do you have? I do not have machines that have dual quad Xeons here for direct comparisons. Thank you. -- ############################################################################# # Jie Chen # Scientific Computing Group # Thomas Jefferson National Accelerator Facility # Newport News, VA 23606 # # chen@jlab.org # (757)269-5046 (office) # (757)269-6248 (fax) #############################################################################