OOM Killer kills PostgreSQL

Hi folks,

We met unexpected PostgreSQL shutdown. After a little investigation we've
discovered that problem is in OOM killer which kills our PostgreSQL.
Unfortunately we can't find query on DB causing this problem. Log is as
below:

May 05 09:05:33 HOST kernel: postgres invoked oom-killer: gfp_mask=0x201da,
order=0, oom_score_adj=-1000
May 05 09:05:34 HOST kernel: postgres cpuset=/ mems_allowed=0
May 05 09:05:34 HOST kernel: CPU: 0 PID: 28286 Comm: postgres Not tainted
3.10.0-1127.el7.x86_64 #1
May 05 09:05:34 HOST kernel: Hardware name: Red Hat KVM, BIOS 0.5.1
01/01/2011
May 05 09:05:34 HOST kernel: Call Trace:
May 05 09:05:34 HOST kernel: [<ffffffffa097ff85>] dump_stack+0x19/0x1b
May 05 09:05:34 HOST kernel: [<ffffffffa097a8a3>] dump_header+0x90/0x229
May 05 09:05:34 HOST kernel: [<ffffffffa050da5b>] ?
cred_has_capability+0x6b/0x120
May 05 09:05:34 HOST kernel: [<ffffffffa03c246e>]
oom_kill_process+0x25e/0x3f0
May 05 09:05:35 HOST kernel: [<ffffffffa0333a41>] ?
cpuset_mems_allowed_intersects+0x21/0x30
May 05 09:05:40 HOST kernel: [<ffffffffa03c1ecd>] ?
oom_unkillable_task+0xcd/0x120
May 05 09:05:42 HOST kernel: [<ffffffffa03c1f76>] ?
find_lock_task_mm+0x56/0xc0
May 05 09:05:42 HOST kernel: [<ffffffffa03c2cc6>] out_of_memory+0x4b6/0x4f0
May 05 09:05:42 HOST kernel: [<ffffffffa097b3c0>]
__alloc_pages_slowpath+0x5db/0x729
May 05 09:05:42 HOST kernel: [<ffffffffa03c9146>]
__alloc_pages_nodemask+0x436/0x450
May 05 09:05:42 HOST kernel: [<ffffffffa0418e18>]
alloc_pages_current+0x98/0x110
May 05 09:05:42 HOST kernel: [<ffffffffa03be377>]
__page_cache_alloc+0x97/0xb0
May 05 09:05:42 HOST kernel: [<ffffffffa03c0f30>] filemap_fault+0x270/0x420
May 05 09:05:42 HOST kernel: [<ffffffffc03c07d6>]
ext4_filemap_fault+0x36/0x50 [ext4]
May 05 09:05:42 HOST kernel: [<ffffffffa03edeea>]
__do_fault.isra.61+0x8a/0x100
May 05 09:05:42 HOST kernel: [<ffffffffa03ee49c>]
do_read_fault.isra.63+0x4c/0x1b0
May 05 09:05:42 HOST kernel: [<ffffffffa03f5d00>]
handle_mm_fault+0xa20/0xfb0
May 05 09:05:42 HOST kernel: [<ffffffffa098d653>]
__do_page_fault+0x213/0x500
May 05 09:05:42 HOST kernel: [<ffffffffa098da26>]
trace_do_page_fault+0x56/0x150
May 05 09:05:42 HOST kernel: [<ffffffffa098cfa2>]
do_async_page_fault+0x22/0xf0
May 05 09:05:42 HOST kernel: [<ffffffffa09897a8>]
async_page_fault+0x28/0x30
May 05 09:05:42 HOST kernel: Mem-Info:
May 05 09:05:42 HOST kernel: active_anon:5382083 inactive_anon:514069
isolated_anon:0
active_file:653
inactive_file:412 isolated_file:75
unevictable:0 dirty:0
writeback:0 unstable:0
slab_reclaimable:120624
slab_unreclaimable:14538
mapped:814755 shmem:816586
pagetables:60496 bounce:0
free:30218 free_pcp:562
free_cma:0

Can You tell me how to find problematic query? Or how to "pimp"
configuration to let db be alive and let us find problematic query?

--

Pozdrawiam
Piotr Włodarczyk