From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753560AbXLEVp0 (ORCPT ); Wed, 5 Dec 2007 16:45:26 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751922AbXLEVpO (ORCPT ); Wed, 5 Dec 2007 16:45:14 -0500 Received: from bombadil.infradead.org ([18.85.46.34]:35473 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751821AbXLEVpM (ORCPT ); Wed, 5 Dec 2007 16:45:12 -0500 Subject: Re: Possible bug from kernel 2.6.22 and above From: Peter Zijlstra To: Jie Chen Cc: linux-kernel@vger.kernel.org, Eric Dumazet , Ingo Molnar , Simon Holm Th??gersen In-Reply-To: <4744966C.900@jlab.org> References: <4744966C.900@jlab.org> Content-Type: text/plain Date: Wed, 05 Dec 2007 21:36:42 +0100 Message-Id: <1196887002.6353.19.camel@lappy> Mime-Version: 1.0 X-Mailer: Evolution 2.12.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 2007-11-21 at 15:34 -0500, Jie Chen wrote: > It is clearly that the synchronization overhead increases as the number > of threads increases in the kernel 2.6.21. But the synchronization > overhead actually decreases as the number of threads increases in the > kernel 2.6.23.8 (We observed the same behavior on kernel 2.6.22 as > well). This certainly is not a correct behavior. The kernels are > configured with CONFIG_SMP, CONFIG_NUMA, CONFIG_SCHED_MC, > CONFIG_PREEMPT_NONE, CONFIG_DISCONTIGMEM set. The complete kernel > configuration file is in the attachment of this e-mail. > > From what we have read, there was a new scheduler (CFS) appeared from > 2.6.22. We are not sure whether the above behavior is caused by the new > scheduler. If I read this correctly, you say that: .22 is the first bad one right? The new scheduler (CFS) was introduced in .23, so it seems another change would be responsible for this.