From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail172.messagelabs.com (mail172.messagelabs.com [216.82.254.3]) by kanga.kvack.org (Postfix) with SMTP id 876396B004D for ; Sun, 28 Jun 2009 09:35:43 -0400 (EDT) Received: by gxk3 with SMTP id 3so5478237gxk.14 for ; Sun, 28 Jun 2009 06:36:49 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <28c262360906280630n557bb182n5079e33d21ea4a83@mail.gmail.com> References: <3901.1245848839@redhat.com> <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> <20090628113246.GA18409@localhost> <28c262360906280630n557bb182n5079e33d21ea4a83@mail.gmail.com> Date: Sun, 28 Jun 2009 22:36:49 +0900 Message-ID: <28c262360906280636l93130ffk14086314e2a6dcb7@mail.gmail.com> Subject: Re: Found the commit that causes the OOMs From: Minchan Kim Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Sender: owner-linux-mm@kvack.org To: Wu Fengguang Cc: Johannes Weiner , David Howells , "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" , "Barnes, Jesse" List-ID: On Sun, Jun 28, 2009 at 10:30 PM, Minchan Kim wrote: > HI, Wu. > > On Sun, Jun 28, 2009 at 8:32 PM, Wu Fengguang wro= te: >> On Sat, Jun 27, 2009 at 08:54:12PM +0800, 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= . =C2=A0It's: >>> > >>> > =C2=A0 =C2=A0 commit 69c854817566db82c362797b4a6521d0b00fe1d8 >>> > =C2=A0 =C2=A0 Author: MinChan Kim >>> > =C2=A0 =C2=A0 Date: =C2=A0 Tue Jun 16 15:32:44 2009 -0700 >>> > >>> > =C2=A0 =C2=A0 =C2=A0 =C2=A0 vmscan: prevent shrinking of active anon = lru list in case of no swap space V3 >>> > >>> > =C2=A0 =C2=A0 =C2=A0 =C2=A0 shrink_zone() can deactivate active anon = pages even if we don't have a >>> > =C2=A0 =C2=A0 =C2=A0 =C2=A0 swap device. =C2=A0Many embedded products= don't have a swap device. =C2=A0So the >>> > =C2=A0 =C2=A0 =C2=A0 =C2=A0 deactivation of anon pages is unnecessary= . >>> > >>> > =C2=A0 =C2=A0 =C2=A0 =C2=A0 This patch prevents unnecessary deactivat= ion of anon lru pages. =C2=A0But, it >>> > =C2=A0 =C2=A0 =C2=A0 =C2=A0 don't prevent aging of anon pages to swap= out. >>> > >>> > =C2=A0 =C2=A0 =C2=A0 =C2=A0 Signed-off-by: Minchan Kim >>> > =C2=A0 =C2=A0 =C2=A0 =C2=A0 Acked-by: KOSAKI Motohiro >>> > =C2=A0 =C2=A0 =C2=A0 =C2=A0 Cc: Johannes Weiner >>> > =C2=A0 =C2=A0 =C2=A0 =C2=A0 Acked-by: Rik van Riel >>> > =C2=A0 =C2=A0 =C2=A0 =C2=A0 Signed-off-by: Andrew Morton >>> > =C2=A0 =C2=A0 =C2=A0 =C2=A0 Signed-off-by: Linus Torvalds >>> > >>> > This exhibits the problem. =C2=A0The previous commit: >>> > >>> > =C2=A0 =C2=A0 commit 35282a2de4e5e4e173ab61aa9d7015886021a821 >>> > =C2=A0 =C2=A0 Author: Brice Goglin >>> > =C2=A0 =C2=A0 Date: =C2=A0 Tue Jun 16 15:32:43 2009 -0700 >>> > >>> > =C2=A0 =C2=A0 =C2=A0 =C2=A0 migration: only migrate_prep() once per m= ove_pages() >>> > >>> > survives 16 iterations of the LTP syscall testsuite without exhibitin= g 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, >>> =C2=A0 =C2=A0 =C2=A0 =C2=A0* Even if we did not try to evict anon pages= at all, we want to >>> =C2=A0 =C2=A0 =C2=A0 =C2=A0* rebalance the anon lru active/inactive rat= io. >>> =C2=A0 =C2=A0 =C2=A0 =C2=A0*/ >>> - =C2=A0 =C2=A0 if (inactive_anon_is_low(zone, sc)) >>> + =C2=A0 =C2=A0 if (inactive_anon_is_low(zone, sc) && nr_swap_pages > 0= ) >>> =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 shrink_active_list(SWA= P_CLUSTER_MAX, zone, sc, priority, 0); >>> >>> =C2=A0 =C2=A0 =C2=A0 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. >> >> Exactly. In Jesse's OOM case, the swap is exhausted. >> total_swap_pages is the better choice in this situation. >> >> Jun 18 07:44:53 jbarnes-g45 kernel: [64377.426766] Active_anon:290797 ac= tive_file:28 inactive_anon:97034 >> Jun 18 07:44:53 jbarnes-g45 kernel: [64377.426767] =C2=A0inactive_file:6= 1 unevictable:11322 dirty:0 writeback:0 unstable:0 >> Jun 18 07:44:53 jbarnes-g45 kernel: [64377.426768] =C2=A0free:3341 slab:= 13776 mapped:5880 pagetables:6851 bounce:0 >> Jun 18 07:44:53 jbarnes-g45 kernel: [64377.426772] DMA free:7776kB min:4= 0kB low:48kB high:60kB active_anon:556kB inactive_anon:524kB >> +active_file:16kB inactive_file:0kB unevictable:0kB present:15340kB page= s_scanned:30 all_unreclaimable? no >> Jun 18 07:44:53 jbarnes-g45 kernel: [64377.426775] lowmem_reserve[]: 0 1= 935 1935 1935 >> Jun 18 07:44:53 jbarnes-g45 kernel: [64377.426781] DMA32 free:5588kB min= :5608kB low:7008kB high:8412kB active_anon:1162632kB >> +inactive_anon:387612kB active_file:96kB inactive_file:256kB unevictable= :45288kB present:1982128kB pages_scanned:980 >> +all_unreclaimable? no >> Jun 18 07:44:53 jbarnes-g45 kernel: [64377.426784] lowmem_reserve[]: 0 0= 0 0 >> Jun 18 07:44:53 jbarnes-g45 kernel: [64377.426787] DMA: 64*4kB 77*8kB 45= *16kB 18*32kB 4*64kB 2*128kB 2*256kB 3*512kB 1*1024kB >> +1*2048kB 0*4096kB =3D 7800kB >> Jun 18 07:44:53 jbarnes-g45 kernel: [64377.426796] DMA32: 871*4kB 149*8k= B 1*16kB 2*32kB 1*64kB 0*128kB 1*256kB 1*512kB 0*1024kB >> +0*2048kB 0*4096kB =3D 5588kB >> Jun 18 07:44:53 jbarnes-g45 kernel: [64377.426804] 151250 total pagecach= e pages >> Jun 18 07:44:53 jbarnes-g45 kernel: [64377.426806] 18973 pages in swap c= ache >> Jun 18 07:44:53 jbarnes-g45 kernel: [64377.426808] Swap cache stats: add= 610640, delete 591667, find 144356/181468 >> Jun 18 07:44:53 jbarnes-g45 kernel: [64377.426810] Free swap =C2=A0=3D 0= kB >> Jun 18 07:44:53 jbarnes-g45 kernel: [64377.426811] Total swap =3D 979956= kB >> Jun 18 07:44:53 jbarnes-g45 kernel: [64377.434828] 507136 pages RAM >> Jun 18 07:44:53 jbarnes-g45 kernel: [64377.434831] 23325 pages reserved >> Jun 18 07:44:53 jbarnes-g45 kernel: [64377.434832] 190892 pages shared >> Jun 18 07:44:53 jbarnes-g45 kernel: [64377.434833] 248816 pages non-shar= ed >> >> >> In David's OOM case, there are two symptoms: >> 1) 70000 unaccounted/leaked pages as found by Andrew >> =C2=A0 (plus rather big number of PG_buddy and pagetable pages) >> 2) almost zero active_file/inactive_file; small inactive_anon; >> =C2=A0 many slab and active_anon pages. >> >> In the situation of (2), the slab cache is _under_ scanned. So David >> got OOM when vmscan should have squeezed some free pages from the slab >> cache. Which is one important side effect of MinChan's patch? > > My patch's side effect is (2). > > My guessing is following as. > > 1. The number of page scanned in shrink_slab is increased in shrink_page_= list. > And it is doubled for mapped page or swapcache. > 2. shrink_page_list is called by shrink_inactive_list > 3. shrink_inactive_list is called by shrink_list > > Look at the shrink_list. > If inactive lru list is low, it always call shrink_active_list not > shrink_inactive_list in case of anon. I missed most important point. My patch's side effect is that it keeps inactive anon's lru low. So I think it is caused by my patch's side effect. > It means it doesn't increased sc->nr_scanned. > Then shrink_slab can't shrink enough slab pages. > So, David OOM have a lot of slab pages and active anon pages. > > Does it make sense ? > If it make sense, we have to change shrink_slab's pressure method. > What do you think ? > > > -- > Kinds regards, > Minchan Kim > --=20 Kinds regards, Minchan Kim -- 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