Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758130Ab0BXUwP (ORCPT ); Wed, 24 Feb 2010 15:52:15 -0500 Received: from ogre.sisk.pl ([217.79.144.158]:44499 "EHLO ogre.sisk.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758041Ab0BXUwN (ORCPT ); Wed, 24 Feb 2010 15:52:13 -0500 From: "Rafael J. Wysocki" To: Alan Jenkins Subject: Re: s2disk hang update Date: Wed, 24 Feb 2010 21:52:55 +0100 User-Agent: KMail/1.12.4 (Linux/2.6.33-rc8-rjw; KDE/4.3.5; x86_64; ; ) Cc: Mel Gorman , hugh.dickins@tiscali.co.uk, Pavel Machek , pm list , "linux-kernel" , Kernel Testers List , KAMEZAWA Hiroyuki , Linux MM References: <9b2b86521001020703v23152d0cy3ba2c08df88c0a79@mail.gmail.com> <201002232213.56455.rjw@sisk.pl> <9b2b86521002240823t126d5ad8nbd292da0f4090e6c@mail.gmail.com> In-Reply-To: <9b2b86521002240823t126d5ad8nbd292da0f4090e6c@mail.gmail.com> MIME-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-2" Content-Transfer-Encoding: 7bit Message-Id: <201002242152.55408.rjw@sisk.pl> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3810 Lines: 98 On Wednesday 24 February 2010, Alan Jenkins wrote: > On 2/23/10, Rafael J. Wysocki wrote: ... > > My guess is that the preallocated memory pages freed by > > free_unnecessary_pages() go into a place from where they cannot be taken for > > subsequent NOIO allocations. I have no idea why that happens though. > > > > To test that theory you can try to change GFP_IOFS to GFP_KERNEL in the > > calls to clear_gfp_allowed_mask() in kernel/power/hibernate.c (and in > > kernel/power/suspend.c for completness). > > Effectively forcing GFP_NOWAIT, so the allocation should fail instead > of hanging? > > It seems to stop the hang, but I don't see any other difference - the > hibernation process isn't stopped earlier, and I don't get any new > kernel messages about allocation failures. I wonder if it's because > GFP_NOWAIT triggers ALLOC_HARDER. > > I have other evidence which argues for your theory: > > [ successful s2disk, with forced NOIO (but not NOWAIT), and test code > as attached ] > > Freezing remaining freezable tasks ... (elapsed 0.01 seconds) done. > 1280 GFP_NOWAIT allocations of order 0 are possible > 640 GFP_NOWAIT allocations of order 1 are possible > 320 GFP_NOWAIT allocations of order 2 are possible > > [ note - 1280 pages is the maximum test allocation used here. The > test code is only accurate when talking about smaller numbers of free > pages ] > > 1280 GFP_KERNEL allocations of order 0 are possible > 640 GFP_KERNEL allocations of order 1 are possible > 320 GFP_KERNEL allocations of order 2 are possible > > PM: Preallocating image memory... > 212 GFP_NOWAIT allocations of order 0 are possible > 102 GFP_NOWAIT allocations of order 1 are possible > 50 GFP_NOWAIT allocations of order 2 are possible > > Freeing all 90083 preallocated pages > (and 0 highmem pages, out of 0) > 190 GFP_NOWAIT allocations of order 0 are possible > 102 GFP_NOWAIT allocations of order 1 are possible > 50 GFP_NOWAIT allocations of order 2 are possible > 1280 GFP_KERNEL allocations of order 0 are possible > 640 GFP_KERNEL allocations of order 1 are possible > 320 GFP_KERNEL allocations of order 2 are possible > done (allocated 90083 pages) > > It looks like you're right and the freed pages are not accessible with > GFP_NOWAIT for some reason. I'd expect this, really. There only is a limited number of pages you can allocate with GFP_NOWAIT. > I also tried a number of test runs with too many applications, and saw this: > > Freeing all 104006 preallocated pages ... > 65 GFP_NOWAIT allocations of order 0 ... > 18 GFP_NOWAIT allocations of order 1 ... > 9 GFP_NOWAIT allocations of order 2 ... > 0 GFP_KERNEL allocations of order 0 are possible > ... Now that's interesting. We've just freed 104006 pages and we can't allocate any, so where did all of these freed pages go, actually? OK, I think I see what the problem is. Quite embarassing, actually ... Can you check if the patch below helps? Rafael --- kernel/power/snapshot.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) Index: linux-2.6/kernel/power/snapshot.c =================================================================== --- linux-2.6.orig/kernel/power/snapshot.c +++ linux-2.6/kernel/power/snapshot.c @@ -1181,7 +1181,7 @@ static void free_unnecessary_pages(void) memory_bm_position_reset(©_bm); - while (to_free_normal > 0 && to_free_highmem > 0) { + while (to_free_normal > 0 || to_free_highmem > 0) { unsigned long pfn = memory_bm_next_pfn(©_bm); struct page *page = pfn_to_page(pfn); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/