On Wed, Apr 18, 2018 at 09:20:02AM +0200, Michal Hocko wrote: > On Wed 18-04-18 11:29:12, Minchan Kim wrote: > > If there are heavy memory pressure, page allocation with __GFP_NOWAIT > > fails easily although it's order-0 request. > > I got below warning 9 times for normal boot. > > > > [ 17.072747] c0 0 <snip >: page allocation failure: order:0, mode:0x2200000(GFP_NOWAIT|__GFP_NOTRACK) > > < snip > > > [ 17.072789] c0 0 Call trace: > > [ 17.072803] c0 0 [<ffffff8009914da4>] dump_backtrace+0x0/0x4 > > [ 17.072813] c0 0 [<ffffff80086bfb5c>] dump_stack+0xa4/0xc0 > > [ 17.072822] c0 0 [<ffffff800831a4f8>] warn_alloc+0xd4/0x15c > > [ 17.072829] c0 0 [<ffffff8008318c3c>] __alloc_pages_nodemask+0xf88/0x10fc > > [ 17.072838] c0 0 [<ffffff8008392b34>] alloc_slab_page+0x40/0x18c > > [ 17.072843] c0 0 [<ffffff8008392acc>] new_slab+0x2b8/0x2e0 > > [ 17.072849] c0 0 [<ffffff800839220c>] ___slab_alloc+0x25c/0x464 > > [ 17.072858] c0 0 [<ffffff8008393dd0>] __kmalloc+0x394/0x498 > > [ 17.072865] c0 0 [<ffffff80083a658c>] memcg_kmem_get_cache+0x114/0x2b8 > > [ 17.072870] c0 0 [<ffffff8008392f38>] kmem_cache_alloc+0x98/0x3e8 > > [ 17.072878] c0 0 [<ffffff8008370be8>] mmap_region+0x3bc/0x8c0 > > [ 17.072884] c0 0 [<ffffff80083707fc>] do_mmap+0x40c/0x43c > > [ 17.072890] c0 0 [<ffffff8008343598>] vm_mmap_pgoff+0x15c/0x1e4 > > [ 17.072898] c0 0 [<ffffff800814be28>] sys_mmap+0xb0/0xc8 > > [ 17.072904] c0 0 [<ffffff8008083730>] el0_svc_naked+0x24/0x28 > > [ 17.072908] c0 0 Mem-Info: > > [ 17.072920] c0 0 active_anon:17124 inactive_anon:193 isolated_anon:0 > > [ 17.072920] c0 0 active_file:7898 inactive_file:712955 isolated_file:55 > > [ 17.072920] c0 0 unevictable:0 dirty:27 writeback:18 unstable:0 > > [ 17.072920] c0 0 slab_reclaimable:12250 slab_unreclaimable:23334 > > [ 17.072920] c0 0 mapped:19310 shmem:212 pagetables:816 bounce:0 > > [ 17.072920] c0 0 free:36561 free_pcp:1205 free_cma:35615 > > [ 17.072933] c0 0 Node 0 active_anon:68496kB inactive_anon:772kB active_file:31592kB inactive_file:2851820kB unevictable:0kB isolated(anon):0kB isolated(file):220kB mapped:77240kB dirty:108kB writeback:72kB shmem:848kB writeback_tmp:0kB unstable:0kB all_unreclaimable? no > > [ 17.072945] c0 0 DMA free:142188kB min:3056kB low:3820kB high:4584kB active_anon:10052kB inactive_anon:12kB active_file:312kB inactive_file:1412620kB unevictable:0kB writepending:0kB present:1781412kB managed:1604728kB mlocked:0kB slab_reclaimable:3592kB slab_unreclaimable:876kB kernel_stack:400kB pagetables:52kB bounce:0kB free_pcp:1436kB local_pcp:124kB free_cma:142492kB > > [ 17.072949] c0 0 lowmem_reserve[]: 0 1842 1842 > > [ 17.072966] c0 0 Normal free:4056kB min:4172kB low:5212kB high:6252kB active_anon:58376kB inactive_anon:760kB active_file:31348kB inactive_file:1439040kB unevictable:0kB writepending:180kB present:2000636kB managed:1923688kB mlocked:0kB slab_reclaimable:45408kB slab_unreclaimable:92460kB kernel_stack:9680kB pagetables:3212kB bounce:0kB free_pcp:3392kB local_pcp:688kB free_cma:0kB > > [ 17.072971] c0 0 lowmem_reserve[]: 0 0 0 > > [ 17.072982] c0 0 DMA: 0*4kB 0*8kB 1*16kB (C) 0*32kB 0*64kB 0*128kB 1*256kB (C) 1*512kB (C) 0*1024kB 1*2048kB (C) 34*4096kB (C) = 142096kB > > [ 17.073024] c0 0 Normal: 228*4kB (UMEH) 172*8kB (UMH) 23*16kB (UH) 24*32kB (H) 5*64kB (H) 1*128kB (H) 0*256kB 0*512kB 0*1024kB 0*2048kB 0*4096kB = 3872kB > > [ 17.073069] c0 0 721350 total pagecache pages > > [ 17.073073] c0 0 0 pages in swap cache > > [ 17.073078] c0 0 Swap cache stats: add 0, delete 0, find 0/0 > > [ 17.073081] c0 0 Free swap = 0kB > > [ 17.073085] c0 0 Total swap = 0kB > > [ 17.073089] c0 0 945512 pages RAM > > [ 17.073093] c0 0 0 pages HighMem/MovableOnly > > [ 17.073097] c0 0 63408 pages reserved > > [ 17.073100] c0 0 51200 pages cma reserved > > > > Let's not make user scared. > > This is not a proper explanation. So what exactly happens when this > allocation fails? I would suggest something like the following > " > __memcg_schedule_kmem_cache_create tries to create a shadow slab cache > and the worker allocation failure is not really critical because we will > retry on the next kmem charge. We might miss some charges but that > shouldn't be critical. The excessive allocation failure report is not > very much helpful. Replace it with a rate limited single line output so > that we know that there is a lot of these failures and that we need to > do something about it in future. > " > > With the last part to be implemented of course. If you want to see warning and catch on it in future, I don't see any reason to change it. Because I didn't see any excessive warning output that it could make system slow unless we did ratelimiting. It was a just report from non-MM guys who have a concern that somethings might go wrong on the system. I just wanted them relax since it's not critical.
