hi all:
I got oom log like at the end of mail from my embedded system.
But the log makes me curious are
a. the free memory size is ok.
        (Normal free:50080kB)
    the pcp hot page is also enough.
        (Normal per-cpu:
        CPU    0: hi:  186, btch:  31 usd:  18
        CPU    1: hi:  186, btch:  31 usd:  22)

b. the water mark should be ok as well.
    in __alloc_pages_may_oom, we use ALLOC_WMARK_HIGH|ALLOC_CPUSET for
watermake checking.
   so in this case:
   free-free_cma = 3192KB > (highmark -= highmark/2 = 2130KB)

But why the oom-killer sill be activated?
appreciate your kind help in advance.

(the kernel version is 3.10)
[ 5515.127555] dialog invoked oom-killer: gfp_mask=0x80d0, order=0,
oom_score_adj=0
[ 5515.136841] CPU: 0 PID: 1535 Comm: com.nvt.dialser Tainted: G
    O 3.10.0+ #28
[ 5515.145711] Backtrace:
[ 5515.149716] [<c00129f8>] (dump_backtrace+0x0/0x114) from
[<c0012c68>] (show_stack+0x20/0x24)
[ 5515.160163]  r6:000080d0 r5:00000000 r4:de3c2000 r3:271ae71c
[ 5515.167278] [<c0012c48>] (show_stack+0x0/0x24) from [<c0550f6c>]
(dump_stack+0x24/0x28)
[ 5515.177129] [<c0550f48>] (dump_stack+0x0/0x28) from [<c010de20>]
(dump_header.isra.13+0x78/0x18c)
[ 5515.188266] [<c010dda8>] (dump_header.isra.13+0x0/0x18c) from
[<c010e384>] (oom_kill_process+0x268/0x3a8)
[ 5515.199405]  r9:00000000 r8:00000000 r7:000080d0 r6:00022d82 r5:000080d0
r4:df679f80
[ 5515.208930] [<c010e11c>] (oom_kill_process+0x0/0x3a8) from
[<c010e884>] (out_of_memory+0x20c/0x2d8)
[ 5515.219014] [<c010e678>] (out_of_memory+0x0/0x2d8) from
[<c011319c>] (__alloc_pages_nodemask+0x928/0x940)
[ 5515.229835] [<c0112874>] (__alloc_pages_nodemask+0x0/0x940) from
[<c01131d4>] (__get_free_pages+0x20/0x3c)
[ 5515.240825] [<c01131b4>] (__get_free_pages+0x0/0x3c) from
[<c0113210>] (get_zeroed_page+0x20/0x24)
[ 5515.250145] [<c01131f0>] (get_zeroed_page+0x0/0x24) from
[<c01adaa8>] (sysfs_follow_link+0x24/0x1a0)
[ 5515.260366] [<c01ada84>] (sysfs_follow_link+0x0/0x1a0) from
[<c015a8fc>] (path_lookupat+0x388/0x800)
[ 5515.270740] [<c015a574>] (path_lookupat+0x0/0x800) from
[<c015ada4>] (filename_lookup+0x30/0xcc)
[ 5515.281052] [<c015ad74>] (filename_lookup+0x0/0xcc) from
[<c015d520>] (user_path_at_empty+0x68/0x90)
[ 5515.291374]  r8:ffffff9c r7:de3c3f60 r6:de3c3eb8 r5:00000001 r4:d3a853c0
r3:de3c3eb8
[ 5515.300401] [<c015d4b8>] (user_path_at_empty+0x0/0x90) from
[<c015d56c>] (user_path_at+0x24/0x2c)
[ 5515.310516]  r8:00000010 r7:be29cd9c r6:ffffff9c r5:00000000 r4:00000001
[ 5515.318228] [<c015d548>] (user_path_at+0x0/0x2c) from [<c014ca9c>]
(SyS_faccessat+0xa4/0x1f4)
[ 5515.327702] [<c014c9f8>] (SyS_faccessat+0x0/0x1f4) from
[<c014cc10>] (SyS_access+0x24/0x28)
[ 5515.336850] [<c014cbec>] (SyS_access+0x0/0x28) from [<c000e380>]
(ret_fast_syscall+0x0/0x48)
[ 5515.346494] Mem-info:
[ 5515.348849] Normal per-cpu:
[ 5515.352345] CPU    0: hi:  186, btch:  31 usd:  18
[ 5515.357785] CPU    1: hi:  186, btch:  31 usd:  22
[ 5515.362814] active_anon:109178 inactive_anon:2272 isolated_anon:0
[ 5515.362814]  active_file:260 inactive_file:961 isolated_file:0
[ 5515.362814]  unevictable:0 dirty:0 writeback:0 unstable:0
[ 5515.362814]  free:12118 slab_reclaimable:1271 slab_unreclaimable:5113
[ 5515.362814]  mapped:2653 shmem:2298 pagetables:979 bounce:0
[ 5515.362814]  free_cma:11605
[ 5515.396900] Normal free:50080kB min:2840kB low:3548kB high:4260kB
active_anon:436712kB inactive_anon:9088kB active_file:1316kB
inactive_file:1636kB unevictable:0kB isolated(anon):0kB
isolated(file):0kB present:585728kB managed:504960kB mlocked:0kB
dirty:0kB writeback:0kB mapped:9624kB shmem:9192kB
slab_reclaimable:5084kB slab_unreclaimable:20452kB kernel_stack:2432kB
pagetables:3916kB unstable:0kB bounce:0kB free_cma:46888kB
writeback_tmp:0kB pages_scanned:24 all_unreclaimable? no
[ 5515.441095] lowmem_reserve[]: 0 0 0
[ 5515.444859] Normal: 4314*4kB (UEMC) 3586*8kB (UMC) 131*16kB (MC)
21*32kB (C) 6*64kB (C) 1*128kB (C) 0*256kB 0*512kB 0*1024kB 0*2048kB
0*4096kB = 49224kB
[ 5515.460587] 3477 total pagecache pages
[ 5515.464648] 0 pages in swap cache
[ 5515.468005] Swap cache stats: add 0, delete 0, find 0/0
[ 5515.473512] Free swap  = 0kB
[ 5515.476665] Total swap = 0kB
[ 5515.497647] 146432 pages of RAM
[ 5515.501295] 13056 free pages
[ 5515.504278] 3712 reserved pages
[ 5515.507864] 4891 slab pages
[ 5515.510899] 396881 pages shared
[ 5515.514303] 0 pages swap cached
[ 5515.668990] Out of memory: Kill process 1260 (app) score 563 or
sacrifice child
[ 5515.678006] Killed process 1277 (idlog) total-vm:511668kB,
anon-rss:61016kB, file-rss:680kB
(*) [Fusion Dispatch  5515.978,466] ( 1260: 1518) SaWMan/Watcher:
Process [0x224b4f00 pid:1277 fusion_id:2 flags:] has exited
ABNORMALLY!