From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750730AbWBXLAV (ORCPT ); Fri, 24 Feb 2006 06:00:21 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750808AbWBXLAV (ORCPT ); Fri, 24 Feb 2006 06:00:21 -0500 Received: from ogre.sisk.pl ([217.79.144.158]:30108 "EHLO ogre.sisk.pl") by vger.kernel.org with ESMTP id S1750730AbWBXLAU (ORCPT ); Fri, 24 Feb 2006 06:00:20 -0500 From: "Rafael J. Wysocki" To: Pavel Machek Subject: Re: Which is simpler? (Was Re: [Suspend2-devel] Re: [ 00/10] [Suspend2] Modules support.) Date: Fri, 24 Feb 2006 11:58:07 +0100 User-Agent: KMail/1.9.1 Cc: Nigel Cunningham , Dmitry Torokhov , Andreas Happe , linux-kernel@vger.kernel.org, Suspend2 Devel List References: <20060201113710.6320.68289.stgit@localhost.localdomain> <200602240927.51338.ncunningham@cyclades.com> <20060223234403.GF1662@elf.ucw.cz> In-Reply-To: <20060223234403.GF1662@elf.ucw.cz> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200602241158.08306.rjw@sisk.pl> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Hi, On Friday 24 February 2006 00:44, Pavel Machek wrote: > > > > > [Because pagecache is freeable, anyway, so it will be freed. Now... I > > > > > have seen some problems where free_some_memory did not free enough, > > > > > and schedule()/retry helped a bit... that probably should be fixed.] > > > > > > > > It seems I need to understand correctly what the difference between what > > > > we do and what Nigel does is. I thought the Nigel's approach was to save > > > > some cache pages to disk first and use the memory occupied by them to > > > > store the image data. If so, is the page cache involved in that or > > > > something else? > > > > > > I believe Nigel only saves pages that could have been freed anyway > > > during phase1. Nigel, correct me here... suspend2 should work on same > > > class of machines swsusp can, but will be able to save caches on > > > machines where swsusp can not save any. > > > > I'm not used to thinking in these terms :). It would be normally be right, > > except that there will be some LRU pages that will never be freed. These > > would allow suspend2 to work in some (not many) cases where swsusp can't. > > It's been ages since I did the intensive testing on the image preparation > > code, but I think that if we free as much memory as we can, we will always > > still have at least a few hundred LRU pages left. That's not much, but on > > machines with less ram, it might make the difference in a greater percentage > > of cases (compared to machines with more ram)? > > Well, pages in LRU should be user pages, and therefore freeable, > AFAICT. It is possible that there's something wrong with freeing in > swsusp1... Well, if all of the pages that Nigel saves before snapshot are freeable in theory, there evidently is something wrong with freeing in swsusp, as we have a testcase in which the user was unable to suspend with swsusp due to the lack of memory and could suspend with suspend2. However, the only thing in swsusp_shrink_memory() that may be wrong is we return -ENOMEM as soon as shrink_all_memory() returns 0. Namely, if shrink_all_memory() can return 0 prematurely (ie. "there still are some freeable pages, but they could not be freed in _this_ call"), we should continue until it returns 0 twice in a row (or something like that). If this doesn't help, we'll have to fix shrink_all_memory() I'm afraid. Greetings, Rafael