From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758067AbYHAMFH (ORCPT ); Fri, 1 Aug 2008 08:05:07 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753899AbYHAME5 (ORCPT ); Fri, 1 Aug 2008 08:04:57 -0400 Received: from relay2.sgi.com ([192.48.171.30]:39286 "EHLO relay.sgi.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1753626AbYHAME4 (ORCPT ); Fri, 1 Aug 2008 08:04:56 -0400 Date: Fri, 1 Aug 2008 07:04:55 -0500 From: Robin Holt To: "Eric W. Biederman" Cc: Robin Holt , linux-kernel@vger.kernel.org, Pavel Emelyanov , Oleg Nesterov , Sukadev Bhattiprolu , Paul Menage , Linus Torvalds , Andrew Morton Subject: Re: [Patch] Scale pidhash_shift/pidhash_size up based on num_possible_cpus(). Message-ID: <20080801120455.GP9663@sgi.com> References: <20080731170022.GE9663@sgi.com> <20080731193204.GG9663@sgi.com> <20080731200835.GK9663@sgi.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.17+20080114 (2008-01-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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). Thanks, Robin