From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754659AbYIEBxT (ORCPT ); Thu, 4 Sep 2008 21:53:19 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754122AbYIEBxB (ORCPT ); Thu, 4 Sep 2008 21:53:01 -0400 Received: from fgwmail5.fujitsu.co.jp ([192.51.44.35]:57830 "EHLO fgwmail5.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751962AbYIEBxA (ORCPT ); Thu, 4 Sep 2008 21:53:00 -0400 Date: Fri, 05 Sep 2008 10:52:10 +0900 From: KOSAKI Motohiro To: Andy Whitcroft Subject: Re: [PATCH 4/4] capture pages freed during direct reclaim for allocation by the reclaimer Cc: kosaki.motohiro@jp.fujitsu.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Mel Gorman , Christoph Lameter In-Reply-To: <20080904144426.GB18776@brain> References: <20080904162900.B262.KOSAKI.MOTOHIRO@jp.fujitsu.com> <20080904144426.GB18776@brain> Message-Id: <20080905105137.5A47.KOSAKI.MOTOHIRO@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit X-Mailer: Becky! ver. 2.42 [ja] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > > Hi Andy, > > > > I like almost part of your patch. > > (at least, I can ack patch 1/4 - 3/4) > > > > So, I worry about OOM risk. > > Can you remember desired page size to capture list (or any other location)? > > if possible, __capture_on_page can avoid to capture unnecessary pages. > > > > So, if __capture_on_page() can make desired size page by buddy merging, > > it can free other pages on capture_list. > > > > In worst case, shrink_zone() is called by very much process at the same time. > > Then, if each process doesn't back few pages, very many pages doesn't be backed. > > The testing we have done pushes the system pretty damn hard, about as > hard as you can. Without the zone watermark checks in capture we would > periodically lose a test to an OOM. Since adding that I have never seen > an OOM, so I am confident we are safe. That said, clearly some wider > testing in -mm would be very desirable to confirm that this does not > tickle OOM for some unexpected workload. > > I think the idea of trying to short-circuit capture once it has a page > of the requisit order or greater is eminently sensible. I suspect we > are going to have trouble getting the information to the right place, > but it is clearly worth investigating. It feels like a logical step on > top of this, so I would propose to do it as a patch on top of this set. > > Thanks for your feedback. Ok. makes sense. Thanks for good patch. Acked-by: KOSAKI Motohiro