From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751690Ab1KOMXY (ORCPT ); Tue, 15 Nov 2011 07:23:24 -0500 Received: from cantor2.suse.de ([195.135.220.15]:44947 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750698Ab1KOMXX (ORCPT ); Tue, 15 Nov 2011 07:23:23 -0500 Date: Tue, 15 Nov 2011 12:23:15 +0000 From: Mel Gorman To: Andrew Morton Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH] mm: Reduce the amount of work done when updating min_free_kbytes Message-ID: <20111115122315.GD27150@suse.de> References: <20111111162119.GP3083@suse.de> <20111114152100.1333a015.akpm@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <20111114152100.1333a015.akpm@linux-foundation.org> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Nov 14, 2011 at 03:21:00PM -0800, Andrew Morton wrote: > On Fri, 11 Nov 2011 16:21:19 +0000 > Mel Gorman wrote: > > > When min_free_kbytes is updated, some pageblocks are marked MIGRATE_RESERVE. > > Ordinarily, this work is unnoticable as it happens early in boot but on > > large machines with 1TB of memory, this has been reported to delay > > boot times, probably due to the NUMA distances involved. > > > > The bulk of the work is due to calling calling pageblock_is_reserved() > > an unnecessary amount of times and accessing far more struct page > > metadata than is necessary. This patch significantly reduces the > > amount of work done by setup_zone_migrate_reserve() improving boot > > times on 1TB machines. > > > > By how much? :) > > (I mainly ask because I'm curious to know how long the kernel takes to > boot on a 1TB machine...) > Good question. I don't have access to the machine but based on the dmesg they posted before and after, this patch reduced boot times by 27 seconds. With only dmesg, I don't know how long it is taking to start services and mount of the filesystem but assuming no major problems or timeouts from drivers it looks like it is taking about 6 minutes to boot. -- Mel Gorman SUSE Labs