From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755811Ab0KRJQc (ORCPT ); Thu, 18 Nov 2010 04:16:32 -0500 Received: from fgwmail5.fujitsu.co.jp ([192.51.44.35]:49669 "EHLO fgwmail5.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752291Ab0KRJQ1 (ORCPT ); Thu, 18 Nov 2010 04:16:27 -0500 X-SecurityPolicyCheck-FJ: OK by FujitsuOutboundMailChecker v1.3.1 Date: Thu, 18 Nov 2010 18:10:48 +0900 From: KAMEZAWA Hiroyuki To: Mel Gorman Cc: Andrea Arcangeli , KOSAKI Motohiro , Andrew Morton , Rik van Riel , Johannes Weiner , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 7/8] mm: compaction: Use the LRU to get a hint on where compaction should start Message-Id: <20101118181048.7bdfbb38.kamezawa.hiroyu@jp.fujitsu.com> In-Reply-To: <1290010969-26721-8-git-send-email-mel@csn.ul.ie> References: <1290010969-26721-1-git-send-email-mel@csn.ul.ie> <1290010969-26721-8-git-send-email-mel@csn.ul.ie> Organization: FUJITSU Co. LTD. X-Mailer: Sylpheed 3.0.3 (GTK+ 2.10.14; i686-pc-mingw32) 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 Wed, 17 Nov 2010 16:22:48 +0000 Mel Gorman wrote: > The end of the LRU stores the oldest known page. Compaction on the other > hand always starts scanning from the start of the zone. This patch uses > the LRU to hint to compaction where it should start scanning from. This > means that compaction will at least start with some old pages reducing > the impact on running processes and reducing the amount of scanning. The > check it makes is racy as the LRU lock is not taken but it should be > harmless as we are not manipulating the lists without the lock. > > Signed-off-by: Mel Gorman Hmm, does this patch make a noticable difference ? Isn't it better to start scan from the biggest free chunk in a zone ? Thanks, -Kame