• Minchan Kim's avatar
    mm: vmscan: scan until it finds eligible pages · 791b48b6
    Minchan Kim authored
    Although there are a ton of free swap and anonymous LRU page in elgible
    zones, OOM happened.
    
      balloon invoked oom-killer: gfp_mask=0x17080c0(GFP_KERNEL_ACCOUNT|__GFP_ZERO|__GFP_NOTRACK), nodemask=(null),  order=0, oom_score_adj=0
      CPU: 7 PID: 1138 Comm: balloon Not tainted 4.11.0-rc6-mm1-zram-00289-ge228d67e9677-dirty #17
      Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Ubuntu-1.8.2-1ubuntu1 04/01/2014
      Call Trace:
       oom_kill_process+0x21d/0x3f0
       out_of_memory+0xd8/0x390
       __alloc_pages_slowpath+0xbc1/0xc50
       __alloc_pages_nodemask+0x1a5/0x1c0
       pte_alloc_one+0x20/0x50
       __pte_alloc+0x1e/0x110
       __handle_mm_fault+0x919/0x960
       handle_mm_fault+0x77/0x120
       __do_page_fault+0x27a/0x550
       trace_do_page_fault+0x43/0x150
       do_async_page_fault+0x2c/0x90
       async_page_fault+0x28/0x30
      Mem-Info:
      active_anon:424716 inactive_anon:65314 isolated_anon:0
       active_file:52 inactive_file:46 isolated_file:0
       unevictable:0 dirty:27 writeback:0 unstable:0
       slab_reclaimable:3967 slab_unreclaimable:4125
       mapped:133 shmem:43 pagetables:1674 bounce:0
       free:4637 free_pcp:225 free_cma:0
      Node 0 active_anon:1698864kB inactive_anon:261256kB active_file:208kB inactive_file:184kB unevictable:0kB isolated(anon):0kB isolated(file):0kB mapped:532kB dirty:108kB writeback:0kB shmem:172kB writeback_tmp:0kB unstable:0kB all_unreclaimable? no
      DMA free:7316kB min:32kB low:44kB high:56kB active_anon:8064kB inactive_anon:0kB active_file:0kB inactive_file:0kB unevictable:0kB writepending:0kB present:15992kB managed:15908kB mlocked:0kB slab_reclaimable:464kB slab_unreclaimable:40kB kernel_stack:0kB pagetables:24kB bounce:0kB free_pcp:0kB local_pcp:0kB free_cma:0kB
      lowmem_reserve[]: 0 992 992 1952
      DMA32 free:9088kB min:2048kB low:3064kB high:4080kB active_anon:952176kB inactive_anon:0kB active_file:36kB inactive_file:0kB unevictable:0kB writepending:88kB present:1032192kB managed:1019388kB mlocked:0kB slab_reclaimable:13532kB slab_unreclaimable:16460kB kernel_stack:3552kB pagetables:6672kB bounce:0kB free_pcp:56kB local_pcp:24kB free_cma:0kB
      lowmem_reserve[]: 0 0 0 959
      Movable free:3644kB min:1980kB low:2960kB high:3940kB active_anon:738560kB inactive_anon:261340kB active_file:188kB inactive_file:640kB unevictable:0kB writepending:20kB present:1048444kB managed:1010816kB mlocked:0kB slab_reclaimable:0kB slab_unreclaimable:0kB kernel_stack:0kB pagetables:0kB bounce:0kB free_pcp:832kB local_pcp:60kB free_cma:0kB
      lowmem_reserve[]: 0 0 0 0
      DMA: 1*4kB (E) 0*8kB 18*16kB (E) 10*32kB (E) 10*64kB (E) 9*128kB (ME) 8*256kB (E) 2*512kB (E) 2*1024kB (E) 0*2048kB 0*4096kB = 7524kB
      DMA32: 417*4kB (UMEH) 181*8kB (UMEH) 68*16kB (UMEH) 48*32kB (UMEH) 14*64kB (MH) 3*128kB (M) 1*256kB (H) 1*512kB (M) 2*1024kB (M) 0*2048kB 0*4096kB = 9836kB
      Movable: 1*4kB (M) 1*8kB (M) 1*16kB (M) 1*32kB (M) 0*64kB 1*128kB (M) 2*256kB (M) 4*512kB (M) 1*1024kB (M) 0*2048kB 0*4096kB = 3772kB
      378 total pagecache pages
      17 pages in swap cache
      Swap cache stats: add 17325, delete 17302, find 0/27
      Free swap  = 978940kB
      Total swap = 1048572kB
      524157 pages RAM
      0 pages HighMem/MovableOnly
      12629 pages reserved
      0 pages cma reserved
      0 pages hwpoisoned
      [ pid ]   uid  tgid total_vm      rss nr_ptes nr_pmds swapents oom_score_adj name
      [  433]     0   433     4904        5      14       3       82             0 upstart-udev-br
      [  438]     0   438    12371        5      27       3      191         -1000 systemd-udevd
    
    With investigation, skipping page of isolate_lru_pages makes reclaim
    void because it returns zero nr_taken easily so LRU shrinking is
    effectively nothing and just increases priority aggressively.  Finally,
    OOM happens.
    
    The problem is that get_scan_count determines nr_to_scan with eligible
    zones so although priority drops to zero, it couldn't reclaim any pages
    if the LRU contains mostly ineligible pages.
    
    get_scan_count:
    
            size = lruvec_lru_size(lruvec, lru, sc->reclaim_idx);
    	size = size >> sc->priority;
    
    Assumes sc->priority is 0 and LRU list is as follows.
    
    	N-N-N-N-H-H-H-H-H-H-H-H-H-H-H-H-H-H-H-H
    
    (Ie, small eligible pages are in the head of LRU but others are
     almost ineligible pages)
    
    In that case, size becomes 4 so VM want to scan 4 pages but 4 pages from
    tail of the LRU are not eligible pages.  If get_scan_count counts
    skipped pages, it doesn't reclaim any pages remained after scanning 4
    pages so it ends up OOM happening.
    
    This patch makes isolate_lru_pages try to scan pages until it encounters
    eligible zones's pages.
    
    [akpm@linux-foundation.org: clean up mind-bending `for' statement.  Tweak comment text]
    Fixes: 3db65812 ("Revert "mm, vmscan: account for skipped pages as a partial scan"")
    Link: http://lkml.kernel.org/r/1494457232-27401-1-git-send-email-minchan@kernel.orgSigned-off-by: default avatarMinchan Kim <minchan@kernel.org>
    Acked-by: default avatarMichal Hocko <mhocko@suse.com>
    Acked-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
    Cc: Mel Gorman <mgorman@techsingularity.net>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    791b48b6
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