From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756597Ab1KNXVD (ORCPT ); Mon, 14 Nov 2011 18:21:03 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:49241 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752638Ab1KNXVB (ORCPT ); Mon, 14 Nov 2011 18:21:01 -0500 Date: Mon, 14 Nov 2011 15:21:00 -0800 From: Andrew Morton To: Mel Gorman 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: <20111114152100.1333a015.akpm@linux-foundation.org> In-Reply-To: <20111111162119.GP3083@suse.de> References: <20111111162119.GP3083@suse.de> X-Mailer: Sylpheed 3.0.2 (GTK+ 2.20.1; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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...)