From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758415AbYHASe6 (ORCPT ); Fri, 1 Aug 2008 14:34:58 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1758606AbYHASdE (ORCPT ); Fri, 1 Aug 2008 14:33:04 -0400 Received: from out02.mta.xmission.com ([166.70.13.232]:35374 "EHLO out02.mta.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757789AbYHASdB (ORCPT ); Fri, 1 Aug 2008 14:33:01 -0400 From: ebiederm@xmission.com (Eric W. Biederman) To: Robin Holt Cc: linux-kernel@vger.kernel.org, Pavel Emelyanov , Oleg Nesterov , Sukadev Bhattiprolu , Paul Menage , Linus Torvalds , Andrew Morton References: <20080731170022.GE9663@sgi.com> <20080731193204.GG9663@sgi.com> <20080731200835.GK9663@sgi.com> <20080801120455.GP9663@sgi.com> Date: Fri, 01 Aug 2008 11:27:20 -0700 In-Reply-To: <20080801120455.GP9663@sgi.com> (Robin Holt's message of "Fri, 1 Aug 2008 07:04:55 -0500") Message-ID: User-Agent: Gnus/5.110006 (No Gnus v0.6) Emacs/21.4 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-SA-Exim-Connect-IP: 24.130.11.59 X-SA-Exim-Mail-From: ebiederm@xmission.com X-Spam-DCC: XMission; sa03 1397; Body=1 Fuz1=1 Fuz2=1 X-Spam-Combo: ;Robin Holt X-Spam-Relay-Country: X-Spam-Report: * -1.8 ALL_TRUSTED Passed through trusted hosts only via SMTP * 0.0 T_TM2_M_HEADER_IN_MSG BODY: T_TM2_M_HEADER_IN_MSG * -1.1 BAYES_05 BODY: Bayesian spam probability is 1 to 5% * [score: 0.0301] * -0.0 DCC_CHECK_NEGATIVE Not listed in DCC * [sa03 1397; Body=1 Fuz1=1 Fuz2=1] * 0.5 XM_Body_Dirty_Words Contains a dirty word * 0.0 XM_SPF_Neutral SPF-Neutral Subject: Re: [Patch] Scale pidhash_shift/pidhash_size up based on num_possible_cpus(). X-SA-Exim-Version: 4.2 (built Thu, 03 Mar 2005 10:44:12 +0100) X-SA-Exim-Scanned: Yes (on mgr1.xmission.com) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Robin Holt writes: > On Thu, Jul 31, 2008 at 03:04:56PM -0700, Eric W. Biederman wrote: >> Robin Holt writes: >> >> > Like so??? >> > >> > I have not tested this yet. >> >> Looks reasonable to me. >> >> In what circumstances was the lookup in the pid hash table with >> long changes causing a performance slowdown?. We don't perform >> a lot of lookups. > > It was initially detected while profiling 'ps' on a 2048p machine that > had 13 kernel threads per cpu. We added a couple more device drivers > which added additional threads. We then started a pthread-on-process > MPI job which had 2048 ranks each with 4 threads (test-case from > customer job). There were misc other processes out there which brought > our task count up to approx 63k. Larger page size helped the problem > (went from 16k to 64k). Large page size? Do you mean larger hash size? What were you measuring that showed improvement with the large hash size? Eric