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[79.181.48.215]) by smtp.gmail.com with ESMTPSA id n3sm3546213wrs.8.2019.12.10.07.24.19 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 10 Dec 2019 07:24:21 -0800 (PST) Date: Tue, 10 Dec 2019 10:24:17 -0500 From: "Michael S. Tsirkin" To: David Hildenbrand Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Yumei Huang , stable@vger.kernel.org, Jason Wang , Jiang Liu , Andrew Morton , virtualization@lists.linux-foundation.org, Igor Mammedov Subject: Re: [PATCH v2] virtio-balloon: fix managed page counts when migrating pages between zones Message-ID: <20191210102353-mutt-send-email-mst@kernel.org> References: <20191205092420.6934-1-david@redhat.com> <13e33ff9-22f2-c02a-811e-2d087e42e1ce@redhat.com> MIME-Version: 1.0 In-Reply-To: <13e33ff9-22f2-c02a-811e-2d087e42e1ce@redhat.com> X-MC-Unique: GnKV8OegOZum4TV1GVviaA-1 X-Mimecast-Spam-Score: 0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: quoted-printable Content-Disposition: inline X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue, Dec 10, 2019 at 02:44:38PM +0100, David Hildenbrand wrote: > On 05.12.19 10:24, David Hildenbrand wrote: > > In case we have to migrate a ballon page to a newpage of another zone, = the > > managed page count of both zones is wrong. Paired with memory offlining > > (which will adjust the managed page count), we can trigger kernel crash= es > > and all kinds of different symptoms. > >=20 > > One way to reproduce: > > 1. Start a QEMU guest with 4GB, no NUMA > > 2. Hotplug a 1GB DIMM and only the memory to ZONE_NORMAL >=20 > s/only/online/ >=20 > as requested by Igor. >=20 > > 3. Inflate the balloon to 1GB > > 4. Unplug the DIMM (be quick, otherwise unmovable data ends up on it) > > 5. Observe /proc/zoneinfo > > Node 0, zone Normal > > pages free 16810 > > min 24848885473806 > > low 18471592959183339 > > high 36918337032892872 > > spanned 262144 > > present 262144 > > managed 18446744073709533486 > > 6. Do anything that requires some memory (e.g., inflate the balloon som= e > > more). The OOM goes crazy and the system crashes > > [ 238.324946] Out of memory: Killed process 537 (login) total-vm:275= 84kB, anon-rss:860kB, file-rss:0kB, shmem-rss:00 > > [ 238.338585] systemd invoked oom-killer: gfp_mask=3D0x100cca(GFP_HI= GHUSER_MOVABLE), order=3D0, oom_score_adj=3D0 > > [ 238.339420] CPU: 0 PID: 1 Comm: systemd Tainted: G D W = 5.4.0-next-20191204+ #75 > > [ 238.340139] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996),= BIOS rel-1.12.0-59-gc9ba5276e321-prebuilt.qemu4 > > [ 238.341121] Call Trace: > > [ 238.341337] dump_stack+0x8f/0xd0 > > [ 238.341630] dump_header+0x61/0x5ea > > [ 238.341942] oom_kill_process.cold+0xb/0x10 > > [ 238.342299] out_of_memory+0x24d/0x5a0 > > [ 238.342625] __alloc_pages_slowpath+0xd12/0x1020 > > [ 238.343024] __alloc_pages_nodemask+0x391/0x410 > > [ 238.343407] pagecache_get_page+0xc3/0x3a0 > > [ 238.343757] filemap_fault+0x804/0xc30 > > [ 238.344083] ? ext4_filemap_fault+0x28/0x42 > > [ 238.344444] ext4_filemap_fault+0x30/0x42 > > [ 238.344789] __do_fault+0x37/0x1a0 > > [ 238.345087] __handle_mm_fault+0x104d/0x1ab0 > > [ 238.345450] handle_mm_fault+0x169/0x360 > > [ 238.345790] do_user_addr_fault+0x20d/0x490 > > [ 238.346154] do_page_fault+0x31/0x210 > > [ 238.346468] async_page_fault+0x43/0x50 > > [ 238.346797] RIP: 0033:0x7f47eba4197e > > [ 238.347110] Code: Bad RIP value. > > [ 238.347387] RSP: 002b:00007ffd7c0c1890 EFLAGS: 00010293 > > [ 238.347834] RAX: 0000000000000002 RBX: 000055d196a20a20 RCX: 00007= f47eba4197e > > [ 238.348437] RDX: 0000000000000033 RSI: 00007ffd7c0c18c0 RDI: 00000= 00000000004 > > [ 238.349047] RBP: 00007ffd7c0c1c20 R08: 0000000000000000 R09: 00000= 00000000033 > > [ 238.349660] R10: 00000000ffffffff R11: 0000000000000293 R12: 00000= 00000000001 > > [ 238.350261] R13: ffffffffffffffff R14: 0000000000000000 R15: 00007= ffd7c0c18c0 > > [ 238.350878] Mem-Info: > > [ 238.351085] active_anon:3121 inactive_anon:51 isolated_anon:0 > > [ 238.351085] active_file:12 inactive_file:7 isolated_file:0 > > [ 238.351085] unevictable:0 dirty:0 writeback:0 unstable:0 > > [ 238.351085] slab_reclaimable:5565 slab_unreclaimable:10170 > > [ 238.351085] mapped:3 shmem:111 pagetables:155 bounce:0 > > [ 238.351085] free:720717 free_pcp:2 free_cma:0 > > [ 238.353757] Node 0 active_anon:12484kB inactive_anon:204kB active_= file:48kB inactive_file:28kB unevictable:0kB iss > > [ 238.355979] Node 0 DMA free:11556kB min:36kB low:48kB high:60kB re= served_highatomic:0KB active_anon:152kB inactivB > > [ 238.358345] lowmem_reserve[]: 0 2955 2884 2884 2884 > > [ 238.358761] Node 0 DMA32 free:2677864kB min:7004kB low:10028kB hig= h:13052kB reserved_highatomic:0KB active_anon:0B > > [ 238.361202] lowmem_reserve[]: 0 0 72057594037927865 72057594037927= 865 72057594037927865 > > [ 238.361888] Node 0 Normal free:193448kB min:99395541895224kB low:7= 3886371836733356kB high:147673348131571488kB reB > > [ 238.364765] lowmem_reserve[]: 0 0 0 0 0 > > [ 238.365101] Node 0 DMA: 7*4kB (U) 5*8kB (UE) 6*16kB (UME) 2*32kB (= UM) 1*64kB (U) 2*128kB (UE) 3*256kB (UME) 2*512B > > [ 238.366379] Node 0 DMA32: 0*4kB 1*8kB (U) 2*16kB (UM) 2*32kB (UM) = 2*64kB (UM) 1*128kB (U) 1*256kB (U) 1*512kB (U)B > > [ 238.367654] Node 0 Normal: 1985*4kB (UME) 1321*8kB (UME) 844*16kB = (UME) 524*32kB (UME) 300*64kB (UME) 138*128kB (B > > [ 238.369184] Node 0 hugepages_total=3D0 hugepages_free=3D0 hugepage= s_surp=3D0 hugepages_size=3D2048kB > > [ 238.369915] 130 total pagecache pages > > [ 238.370241] 0 pages in swap cache > > [ 238.370533] Swap cache stats: add 0, delete 0, find 0/0 > > [ 238.370981] Free swap =3D 0kB > > [ 238.371239] Total swap =3D 0kB > > [ 238.371488] 1048445 pages RAM > > [ 238.371756] 0 pages HighMem/MovableOnly > > [ 238.372090] 306992 pages reserved > > [ 238.372376] 0 pages cma reserved > > [ 238.372661] 0 pages hwpoisoned > >=20 > > In another instance (older kernel), I was able to observe this > > (negative page count :/): > > [ 180.896971] Offlined Pages 32768 > > [ 182.667462] Offlined Pages 32768 > > [ 184.408117] Offlined Pages 32768 > > [ 186.026321] Offlined Pages 32768 > > [ 187.684861] Offlined Pages 32768 > > [ 189.227013] Offlined Pages 32768 > > [ 190.830303] Offlined Pages 32768 > > [ 190.833071] Built 1 zonelists, mobility grouping on. Total pages:= -36920272750453009 > >=20 > > In another instance (older kernel), I was no longer able to start any > > process: > > [root@vm ~]# [ 214.348068] Offlined Pages 32768 > > [ 215.973009] Offlined Pages 32768 > > cat /proc/meminfo > > -bash: fork: Cannot allocate memory > > [root@vm ~]# cat /proc/meminfo > > -bash: fork: Cannot allocate memory > >=20 > > Fix it by properly adjusting the managed page count when migrating if > > the zone changed. The managed page count of the zones now looks after > > unplug of the DIMM (and after deflating the balloon) just like before > > inflating the balloon (and plugging+onlining the DIMM). > >=20 > > We'll temporarily modify the totalram page count. If this ever becomes = a > > problem, we can fine tune by providing helpers that don't touch > > the totalram pages (e.g., adjust_zone_managed_page_count()). > >=20 > > Reported-by: Yumei Huang > > Fixes: 3dcc0571cd64 ("mm: correctly update zone->managed_pages") > > Cc: # v3.11+ > > Cc: "Michael S. Tsirkin" > > Cc: Jason Wang > > Cc: Jiang Liu > > Cc: Andrew Morton > > Cc: virtualization@lists.linux-foundation.org > > Signed-off-by: David Hildenbrand > > --- > >=20 > > v1 -> v2: > > - Adjust count before enquing newpage (and it possibly gets free form t= he > > balloon) > > - Check if the zone changed > >=20 > > --- > > drivers/virtio/virtio_balloon.c | 7 +++++++ > > 1 file changed, 7 insertions(+) > >=20 > > diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_ba= lloon.c > > index 15b7f1d8c334..3078e1ac2a8f 100644 > > --- a/drivers/virtio/virtio_balloon.c > > +++ b/drivers/virtio/virtio_balloon.c > > @@ -722,6 +722,13 @@ static int virtballoon_migratepage(struct balloon_= dev_info *vb_dev_info, > > =20 > > =09get_page(newpage); /* balloon reference */ > > =20 > > +=09/* fixup the managed page count (esp. of the zone) */ >=20 > /* > * When we migrate to a different zone, we have to adjust the managed > * page count of both involved zones. > */ >=20 > as requested by Michael. >=20 >=20 > @Michael, if there are no further comments, shall I resend? Also, what does it have to do with deflate on oom? Why is it true we don't need to do it then? > --=20 > Thanks, >=20 > David / dhildenb