From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail143.messagelabs.com (mail143.messagelabs.com [216.82.254.35]) by kanga.kvack.org (Postfix) with ESMTP id 104656B004D for ; Sat, 27 Jun 2009 11:39:14 -0400 (EDT) Date: Sat, 27 Jun 2009 17:36:30 +0200 From: Johannes Weiner Subject: Re: Found the commit that causes the OOMs Message-ID: <20090627153630.GA6803@cmpxchg.org> References: <20090624023251.GA16483@localhost> <20090620043303.GA19855@localhost> <32411.1245336412@redhat.com> <20090517022327.280096109@intel.com> <2015.1245341938@redhat.com> <20090618095729.d2f27896.akpm@linux-foundation.org> <7561.1245768237@redhat.com> <26537.1246086769@redhat.com> <20090627125412.GA1667@cmpxchg.org> <28c262360906270650v6c276591u417d64573ecfba29@mail.gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <28c262360906270650v6c276591u417d64573ecfba29@mail.gmail.com> Sender: owner-linux-mm@kvack.org To: Minchan Kim Cc: David Howells , Wu Fengguang , "riel@redhat.com" , Andrew Morton , LKML , Christoph Lameter , KOSAKI Motohiro , "peterz@infradead.org" , "tytso@mit.edu" , "linux-mm@kvack.org" , "elladan@eskimo.com" , "npiggin@suse.de" List-ID: On Sat, Jun 27, 2009 at 10:50:25PM +0900, Minchan Kim wrote: > Hi, Hannes. > > On Sat, Jun 27, 2009 at 9:54 PM, Johannes Weiner wrote: > > On Sat, Jun 27, 2009 at 08:12:49AM +0100, David Howells wrote: > >> > >> I've managed to bisect things to find the commit that causes the OOMs. A It's: > >> > >> A A A commit 69c854817566db82c362797b4a6521d0b00fe1d8 > >> A A A Author: MinChan Kim > >> A A A Date: A Tue Jun 16 15:32:44 2009 -0700 > >> > >> A A A A A vmscan: prevent shrinking of active anon lru list in case of no swap space V3 > >> > >> A A A A A shrink_zone() can deactivate active anon pages even if we don't have a > >> A A A A A swap device. A Many embedded products don't have a swap device. A So the > >> A A A A A deactivation of anon pages is unnecessary. > >> > >> A A A A A This patch prevents unnecessary deactivation of anon lru pages. A But, it > >> A A A A A don't prevent aging of anon pages to swap out. > >> > >> A A A A A Signed-off-by: Minchan Kim > >> A A A A A Acked-by: KOSAKI Motohiro > >> A A A A A Cc: Johannes Weiner > >> A A A A A Acked-by: Rik van Riel > >> A A A A A Signed-off-by: Andrew Morton > >> A A A A A Signed-off-by: Linus Torvalds > >> > >> This exhibits the problem. A The previous commit: > >> > >> A A A commit 35282a2de4e5e4e173ab61aa9d7015886021a821 > >> A A A Author: Brice Goglin > >> A A A Date: A Tue Jun 16 15:32:43 2009 -0700 > >> > >> A A A A A migration: only migrate_prep() once per move_pages() > >> > >> survives 16 iterations of the LTP syscall testsuite without exhibiting the > >> problem. > > > > Here is the patch in question: > > > > diff --git a/mm/vmscan.c b/mm/vmscan.c > > index 7592d8e..879d034 100644 > > --- a/mm/vmscan.c > > +++ b/mm/vmscan.c > > @@ -1570,7 +1570,7 @@ static void shrink_zone(int priority, struct zone *zone, > > A A A A * Even if we did not try to evict anon pages at all, we want to > > A A A A * rebalance the anon lru active/inactive ratio. > > A A A A */ > > - A A A if (inactive_anon_is_low(zone, sc)) > > + A A A if (inactive_anon_is_low(zone, sc) && nr_swap_pages > 0) > > A A A A A A A A shrink_active_list(SWAP_CLUSTER_MAX, zone, sc, priority, 0); > > > > A A A A throttle_vm_writeout(sc->gfp_mask); > > > > When this was discussed, I think we missed that nr_swap_pages can > > actually get zero on swap systems as well and this should have been > > total_swap_pages - otherwise we also stop balancing the two anon lists > > when swap is _full_ which was not the intention of this change at all. > > At that time we considered it so that we didn't prevent anon list > aging for background reclaim. > Do you think it is not enough ? With a heavy multiprocess anon load, direct reclaimers will likely reuse the reclaimed pages for anon mappings, so you have a handful of processes shuffling pages on the active list and only one thread that tries to balance. I can imagine that it can not keep up for long. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org