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The problem

A server crashed after multiple "Out of memory" messages and I am trying to pinpoint the culprit. If it is in userland - which process. If it is in the kernel - which kernel module.

Details

I am trying to find out how to use the crash utility to investigate what triggered an OOM on a server.

As part of the installation of a fresh pair of servers, I started the initialization of a 14TB DRBD device. Around that time, while playing with the DRBD syncer rate configuration, and bringing some of the bonded network interfaces up and down, one of the servers crashed. Over a 30 seconds period it produced 39 Out of memory: Kill process #### messages. Then it crashed with:

Kernel panic - not syncing: Out of memory and no killable processes...

The system crash triggered a kdump. Now I have a nice vmcore.flat file which should be straightforward to use to investigate the issue, but I have hard time finding out where all the memory went.

The only resource I am aware of is Dedoimedo's site, which has nice instructions, and the Kernel Crash Book. These also happen to be the only resources suggested in the answers so I assume that crash is the only way to investigate.

If there is another way to do a post-mortem on the incident, I am willing to accept it. It is just that crash is the only utility that I am aware of. All I have right now is the vmcore.flat file, and all I need to know is which component ate up all that memory. I am suspecting a kernel module problem, and more specifically one of the bonding module (as it got triggered as I brought an interface down), the DRBD module (version 8.3.15 built out of tree on CentOS 6.3), or one of the 10G ethernet modules (mlnx_en built out of tree which is the interface I brought down, or the in-tree bnx2x which is the interface that remained active). All I need to know is if there is a way to verify my suspicion.

So far, I only managed to extract the following information with the crash utility:

Checked how much memory is used

$ crash /usr/lib/debug/lib/modules/2.6.32-279.5.2.el6.x86_64/vmlinux vmcore.flat
....
crash> kmem -i
              PAGES        TOTAL      PERCENTAGE
 TOTAL MEM  16482587      62.9 GB         ----
      FREE    54610     213.3 MB    0% of TOTAL MEM
      USED  16427977      62.7 GB   99% of TOTAL MEM
    SHARED     4683      18.3 MB    0% of TOTAL MEM
   BUFFERS      118       472 KB    0% of TOTAL MEM
    CACHED       82       328 KB    0% of TOTAL MEM
      SLAB    46635     182.2 MB    0% of TOTAL MEM

TOTAL SWAP        0            0         ----
 SWAP USED        0            0  100% of TOTAL SWAP
 SWAP FREE        0            0    0% of TOTAL SWAP

Obviously, it ran out of memory. All 64G is gone... but where?

Tried to see see if any processes are leaking memory

The only command that seems relevant is ps (this is the ps subcommand of crash). It shows nothing abnormal, but it also shows nothing about kernel threads.

crash> ps
   PID    PPID  CPU       TASK        ST  %MEM     VSZ    RSS  COMM
      0      0   0  ffffffff81a8d020  RU   0.0       0      0  [swapper]
>     0      0   1  ffff88102c456040  RU   0.0       0      0  [swapper]
>     0      0   2  ffff88082c772aa0  RU   0.0       0      0  [swapper]
>     0      0   3  ffff88102c456aa0  RU   0.0       0      0  [swapper]
      0      0   4  ffff88082c7b8ae0  RU   0.0       0      0  [swapper]
>     0      0   5  ffff88102c457500  RU   0.0       0      0  [swapper]
>     0      0   6  ffff88082c7d6aa0  RU   0.0       0      0  [swapper]
>     0      0   7  ffff88102c506080  RU   0.0       0      0  [swapper]
>     0      0   8  ffff88082c016ae0  RU   0.0       0      0  [swapper]
>     0      0   9  ffff88102c506ae0  RU   0.0       0      0  [swapper]
>     0      0  10  ffff88082c05caa0  RU   0.0       0      0  [swapper]
>     0      0  11  ffff88102c507540  RU   0.0       0      0  [swapper]
>     0      0  12  ffff88082c09cae0  RU   0.0       0      0  [swapper]
.....
   4926      1   5  ffff880828a38ae0  ??   0.0       0      0  mingetty
   4928      1   1  ffff88102a4e8040  ??   0.0       0      0  mingetty
   4930      1  19  ffff880827af4080  ??   0.0       0      0  mingetty
   4932      1   2  ffff88100f122040  ??   0.0       0      0  mingetty
   4934      1  18  ffff8810296ea080  ??   0.0       0      0  mingetty
   4936   1047   4  ffff880ff342d540  IN   0.0   11184    948  udevd
   4937   1047   5  ffff88082a240080  IN   0.0   11184    948  udevd
   5060   3772   2  ffff88082881d540  ??   0.0       0      0  sshd
   5078      1   1  ffff88100f060ae0  ??   0.0       0      0  sshd
   5079      1   1  ffff88082b882ae0  ??   0.0       0      0  bash

And if I take out the kernel threads (which all show zeroes for %MEM anyway), we can see that I was left with almost nothing running in the end:

crash> ps -u
   PID    PPID  CPU       TASK        ST  %MEM     VSZ    RSS  COMM
      1      0   1  ffff88082c41b500  ??   0.0   19348    348  init
   1047      1   2  ffff881029524040  IN   0.0   11188    948  udevd
   3171      1   3  ffff880826ccaaa0  IN   0.0   27636    240  auditd
   3172      1  17  ffff881029d1b500  IN   0.0   27636    240  auditd
>  3772      1   0  ffff88102b257500  RU   0.0   64072    668  sshd
   4800      1   0  ffff88100f061540  ??   0.0       0      0  dsm_om_shrsvcd
   4842      1  16  ffff88100f012ae0  ??   0.0       0      0  cmcld
   4854      1  17  ffff88082a241540  ??   0.0       0      0  cmlogd
   4855      1   3  ffff88082796cae0  ??   0.0       0      0  cmfileassistd
   4856      1  18  ffff88082809d500  ??   0.0       0      0  cmnetd
   4860      1   0  ffff88082705aae0  ??   0.0       0      0  cmresourced
   4924      1   9  ffff88102a4e8aa0  ??   0.0       0      0  mingetty
   4926      1   5  ffff880828a38ae0  ??   0.0       0      0  mingetty
   4928      1   1  ffff88102a4e8040  ??   0.0       0      0  mingetty
   4930      1  19  ffff880827af4080  ??   0.0       0      0  mingetty
   4932      1   2  ffff88100f122040  ??   0.0       0      0  mingetty
   4934      1  18  ffff8810296ea080  ??   0.0       0      0  mingetty
   4936   1047   4  ffff880ff342d540  IN   0.0   11184    948  udevd
   4937   1047   5  ffff88082a240080  IN   0.0   11184    948  udevd
   5060   3772   2  ffff88082881d540  ??   0.0       0      0  sshd
   5078      1   1  ffff88100f060ae0  ??   0.0       0      0  sshd
   5079      1   1  ffff88082b882ae0  ??   0.0       0      0  bash
   5257      1   1  ffff8808279e6aa0  ??   0.0       0      0  jnx_mlnxsnmp_da

Update:

Including some more output, as suggested by Soham. Unfortunately I cannot derive any further conclusions from it. The best I can do is suspect something in the kernel leaking memory, since the userland processes are almost all dead anyway.

The (almost full) output of log -m is here

crash> ps -G | tail -n +2 | cut -b2- | gawk '{mem += $8} END {print "total " mem/1048576 "GB"}'
total 0.00391006GB

Note that almost all userland processes are dead at this time, so the low reported usage is expected.

Out of memory messages:

As I mentioned above, there are 39 "Out of memory:" messages, and here they are:

crash> log -m | grep Out
<3>[  223.556616] Out of memory: Kill process 3189 (portreserve) score 1 or sacrifice child
<3>[  223.787234] Out of memory: Kill process 3196 (rsyslogd) score 1 or sacrifice child
<3>[  224.237119] Out of memory: Kill process 3728 (dbus-daemon) score 1 or sacrifice child
<3>[  228.771770] Out of memory: Kill process 3758 (snmpd) score 1 or sacrifice child
<3>[  229.033466] Out of memory: Kill process 3782 (xinetd) score 1 or sacrifice child
<3>[  229.257710] Out of memory: Kill process 3782 (xinetd) score 1 or sacrifice child
<3>[  229.484321] Out of memory: Kill process 3782 (xinetd) score 1 or sacrifice child
<3>[  229.711169] Out of memory: Kill process 3782 (xinetd) score 1 or sacrifice child
<3>[  229.934955] Out of memory: Kill process 3801 (cmproxyd) score 1 or sacrifice child
<3>[  230.159542] Out of memory: Kill process 3812 (ntpd) score 1 or sacrifice child
<3>[  230.382083] Out of memory: Kill process 3953 (master) score 1 or sacrifice child
<3>[  230.606613] Out of memory: Kill process 3953 (master) score 1 or sacrifice child
<3>[  230.829515] Out of memory: Kill process 3953 (master) score 1 or sacrifice child
<3>[  230.832105] Out of memory: Kill process 3961 (crond) score 1 or sacrifice child
<3>[  236.749746] Out of memory: Kill process 3974 (atd) score 1 or sacrifice child
<3>[  236.969421] Out of memory: Kill process 4272 (dsm_sa_datamgrd) score 1 or sacrifice child
<3>[  237.192102] Out of memory: Kill process 4492 (dsm_sa_datamgrd) score 1 or sacrifice child
<3>[  237.746301] Out of memory: Kill process 4552 (dsm_sa_eventmgr) score 1 or sacrifice child
<3>[  237.968308] Out of memory: Kill process 4613 (dsm_sa_snmpd) score 1 or sacrifice child
<3>[  238.190550] Out of memory: Kill process 4614 (dsm_sa_snmpd) score 1 or sacrifice child
<3>[  238.644020] Out of memory: Kill process 4643 (dsm_om_connsvcd) score 1 or sacrifice child
<3>[  238.865658] Out of memory: Kill process 4643 (dsm_om_connsvcd) score 1 or sacrifice child
<3>[  251.285450] Out of memory: Kill process 4643 (dsm_om_connsvcd) score 1 or sacrifice child
<3>[  251.506601] Out of memory: Kill process 4800 (dsm_om_shrsvcd) score 1 or sacrifice child
<3>[  251.727570] Out of memory: Kill process 4842 (cmcld) score 1 or sacrifice child
<3>[  251.947085] Out of memory: Kill process 4842 (cmcld) score 1 or sacrifice child
<3>[  252.167096] Out of memory: Kill process 4854 (cmlogd) score 1 or sacrifice child
<3>[  252.384090] Out of memory: Kill process 4855 (cmfileassistd) score 1 or sacrifice child
<3>[  252.603324] Out of memory: Kill process 4924 (mingetty) score 1 or sacrifice child
<3>[  252.820757] Out of memory: Kill process 4926 (mingetty) score 1 or sacrifice child
<3>[  253.037558] Out of memory: Kill process 4928 (mingetty) score 1 or sacrifice child
<3>[  253.254908] Out of memory: Kill process 4930 (mingetty) score 1 or sacrifice child
<3>[  253.257391] Out of memory: Kill process 4932 (mingetty) score 1 or sacrifice child
<3>[  253.259357] Out of memory: Kill process 4934 (mingetty) score 1 or sacrifice child
<3>[  253.261353] Out of memory: Kill process 5060 (sshd) score 1 or sacrifice child
<3>[  253.263365] Out of memory: Kill process 5060 (sshd) score 1 or sacrifice child
<3>[  253.264392] Out of memory: Kill process 5079 (bash) score 1 or sacrifice child
<3>[  253.266352] Out of memory: Kill process 5257 (jnx_mlnxsnmp_da) score 1 or sacrifice child
<0>[  253.529344] Kernel panic - not syncing: Out of memory and no killable processes...

sys output:

crash> sys
      KERNEL: /usr/lib/debug/lib/modules/2.6.32-279.5.2.el6.x86_64/vmlinux
    DUMPFILE: pcdata03.vmcore.flat  [PARTIAL DUMP]
        CPUS: 32
        DATE: Wed Feb  6 02:11:52 2013
      UPTIME: 00:04:12
LOAD AVERAGE: 3.03, 0.95, 0.34
       TASKS: 578
    NODENAME: ....
     RELEASE: 2.6.32-279.5.2.el6.x86_64
     VERSION: #1 SMP Fri Aug 24 01:07:11 UTC 2012
     MACHINE: x86_64  (2700 Mhz)
      MEMORY: 64 GB
       PANIC: "[  253.529344] Kernel panic - not syncing: Out of memory and no killable processes..."

kmem -z

crash> kmem -z
NODE: 0  ZONE: 0  ADDR: ffff88000000a0c0  NAME: "DMA"
  SIZE: 4095  PRESENT: 3839  MIN/LOW/HIGH: 5/6/7
  VM_STAT:
          NR_FREE_PAGES: 3936
       NR_INACTIVE_ANON: 0
         NR_ACTIVE_ANON: 0
       NR_INACTIVE_FILE: 0
         NR_ACTIVE_FILE: 0
         NR_UNEVICTABLE: 0
               NR_MLOCK: 0
          NR_ANON_PAGES: 0
         NR_FILE_MAPPED: 0
          NR_FILE_PAGES: 0
          NR_FILE_DIRTY: 0
           NR_WRITEBACK: 0
    NR_SLAB_RECLAIMABLE: 0
  NR_SLAB_UNRECLAIMABLE: 0
           NR_PAGETABLE: 0
        NR_KERNEL_STACK: 0
        NR_UNSTABLE_NFS: 0
              NR_BOUNCE: 0
        NR_VMSCAN_WRITE: 0
    NR_VMSCAN_IMMEDIATE: 0
      NR_WRITEBACK_TEMP: 0
       NR_ISOLATED_ANON: 0
       NR_ISOLATED_FILE: 0
               NR_SHMEM: 0
               NUMA_HIT: 0
              NUMA_MISS: 0
           NUMA_FOREIGN: 0
    NUMA_INTERLEAVE_HIT: 0
             NUMA_LOCAL: 0
             NUMA_OTHER: 0
NR_ANON_TRANSPARENT_HUGEPAGES: 0

NODE: 0  ZONE: 1  ADDR: ffff880000012780  NAME: "DMA32"
  SIZE: 1044480  PRESENT: 756520  MIN/LOW/HIGH: 1030/1287/1545
  VM_STAT:
          NR_FREE_PAGES: 30117
       NR_INACTIVE_ANON: 0
         NR_ACTIVE_ANON: 0
       NR_INACTIVE_FILE: 1
         NR_ACTIVE_FILE: 0
         NR_UNEVICTABLE: 0
               NR_MLOCK: 0
          NR_ANON_PAGES: 0
         NR_FILE_MAPPED: 0
          NR_FILE_PAGES: 1
          NR_FILE_DIRTY: 0
           NR_WRITEBACK: 0
    NR_SLAB_RECLAIMABLE: 4
  NR_SLAB_UNRECLAIMABLE: 4150
           NR_PAGETABLE: 0
        NR_KERNEL_STACK: 0
        NR_UNSTABLE_NFS: 0
              NR_BOUNCE: 0
        NR_VMSCAN_WRITE: 0
    NR_VMSCAN_IMMEDIATE: 0
      NR_WRITEBACK_TEMP: 0
       NR_ISOLATED_ANON: 0
       NR_ISOLATED_FILE: 0
               NR_SHMEM: 0
               NUMA_HIT: 575606
              NUMA_MISS: 3
           NUMA_FOREIGN: 0
    NUMA_INTERLEAVE_HIT: 0
             NUMA_LOCAL: 575598
             NUMA_OTHER: 11
NR_ANON_TRANSPARENT_HUGEPAGES: 0

NODE: 0  ZONE: 2  ADDR: ffff88000001ae40  NAME: "Normal"
  SIZE: 7602176  PRESENT: 7498240  MIN/LOW/HIGH: 10217/12771/15325
  VM_STAT:
          NR_FREE_PAGES: 10443
       NR_INACTIVE_ANON: 134
         NR_ACTIVE_ANON: 197
       NR_INACTIVE_FILE: -47
         NR_ACTIVE_FILE: 42
         NR_UNEVICTABLE: 0
               NR_MLOCK: 0
          NR_ANON_PAGES: 219
         NR_FILE_MAPPED: 115
          NR_FILE_PAGES: 45
          NR_FILE_DIRTY: 0
           NR_WRITEBACK: 0
    NR_SLAB_RECLAIMABLE: 908
  NR_SLAB_UNRECLAIMABLE: 18771
           NR_PAGETABLE: 91
        NR_KERNEL_STACK: 556
        NR_UNSTABLE_NFS: 0
              NR_BOUNCE: 0
        NR_VMSCAN_WRITE: 0
    NR_VMSCAN_IMMEDIATE: 0
      NR_WRITEBACK_TEMP: 0
       NR_ISOLATED_ANON: 0
       NR_ISOLATED_FILE: 0
               NR_SHMEM: 34
               NUMA_HIT: 8243991
              NUMA_MISS: 648
           NUMA_FOREIGN: 4593726
    NUMA_INTERLEAVE_HIT: 20066
             NUMA_LOCAL: 8243829
             NUMA_OTHER: 810
NR_ANON_TRANSPARENT_HUGEPAGES: 0

NODE: 0  ZONE: 3  ADDR: ffff880000023500  NAME: "Movable"
  [unpopulated]

NODE: 1  ZONE: 0  ADDR: ffff880840000040  NAME: "DMA"
  [unpopulated]

NODE: 1  ZONE: 1  ADDR: ffff880840008700  NAME: "DMA32"
  [unpopulated]

NODE: 1  ZONE: 2  ADDR: ffff880840010dc0  NAME: "Normal"
  SIZE: 8388608  PRESENT: 8273920  MIN/LOW/HIGH: 11274/14092/16911
  VM_STAT:
          NR_FREE_PAGES: 10114
       NR_INACTIVE_ANON: 417
         NR_ACTIVE_ANON: 83
       NR_INACTIVE_FILE: 47
         NR_ACTIVE_FILE: 32
         NR_UNEVICTABLE: 0
               NR_MLOCK: 0
          NR_ANON_PAGES: 436
         NR_FILE_MAPPED: 22
          NR_FILE_PAGES: 154
          NR_FILE_DIRTY: 0
           NR_WRITEBACK: 0
    NR_SLAB_RECLAIMABLE: 863
  NR_SLAB_UNRECLAIMABLE: 21939
           NR_PAGETABLE: 134
        NR_KERNEL_STACK: 27
        NR_UNSTABLE_NFS: 0
              NR_BOUNCE: 0
        NR_VMSCAN_WRITE: 3
    NR_VMSCAN_IMMEDIATE: 5
      NR_WRITEBACK_TEMP: 0
       NR_ISOLATED_ANON: 0
       NR_ISOLATED_FILE: 23
               NR_SHMEM: 20
               NUMA_HIT: 4332488
              NUMA_MISS: 4593726
           NUMA_FOREIGN: 665
    NUMA_INTERLEAVE_HIT: 20007
             NUMA_LOCAL: 4309300
             NUMA_OTHER: 4616914
NR_ANON_TRANSPARENT_HUGEPAGES: 0

NODE: 1  ZONE: 3  ADDR: ffff880840019480  NAME: "Movable"
  [unpopulated]

kmem -f

crash> kmem -f
NODE
  0
ZONE  NAME        SIZE    FREE      MEM_MAP       START_PADDR  START_MAPNR
  0   DMA         4095    3936  ffffea0000000038      1000          0     
AREA    SIZE  FREE_AREA_STRUCT  BLOCKS  PAGES
  0       4k  ffff880000012128       2      2
  0       4k  ffff880000012138       0      0
  0       4k  ffff880000012148       0      0
  0       4k  ffff880000012158       0      0
  0       4k  ffff880000012168       0      0
  1       8k  ffff880000012180       1      2
  1       8k  ffff880000012190       0      0
  1       8k  ffff8800000121a0       0      0
  1       8k  ffff8800000121b0       0      0
  1       8k  ffff8800000121c0       0      0
  2      16k  ffff8800000121d8       1      4
  2      16k  ffff8800000121e8       0      0
  2      16k  ffff8800000121f8       0      0
  2      16k  ffff880000012208       0      0
  2      16k  ffff880000012218       0      0
  3      32k  ffff880000012230       1      8
  3      32k  ffff880000012240       0      0
  3      32k  ffff880000012250       0      0
  3      32k  ffff880000012260       0      0
  3      32k  ffff880000012270       0      0
  4      64k  ffff880000012288       1     16
  4      64k  ffff880000012298       0      0
  4      64k  ffff8800000122a8       0      0
  4      64k  ffff8800000122b8       0      0
  4      64k  ffff8800000122c8       0      0
  5     128k  ffff8800000122e0       0      0
  5     128k  ffff8800000122f0       0      0
  5     128k  ffff880000012300       0      0
  5     128k  ffff880000012310       0      0
  5     128k  ffff880000012320       0      0
  6     256k  ffff880000012338       1     64
  6     256k  ffff880000012348       0      0
  6     256k  ffff880000012358       0      0
  6     256k  ffff880000012368       0      0
  6     256k  ffff880000012378       0      0
  7     512k  ffff880000012390       0      0
  7     512k  ffff8800000123a0       0      0
  7     512k  ffff8800000123b0       0      0
  7     512k  ffff8800000123c0       0      0
  7     512k  ffff8800000123d0       0      0
  8    1024k  ffff8800000123e8       1    256
  8    1024k  ffff8800000123f8       0      0
  8    1024k  ffff880000012408       0      0
  8    1024k  ffff880000012418       0      0
  8    1024k  ffff880000012428       0      0
  9    2048k  ffff880000012440       0      0
  9    2048k  ffff880000012450       0      0
  9    2048k  ffff880000012460       0      0
  9    2048k  ffff880000012470       1    512
  9    2048k  ffff880000012480       0      0
 10    4096k  ffff880000012498       0      0
 10    4096k  ffff8800000124a8       0      0
 10    4096k  ffff8800000124b8       3   3072
 10    4096k  ffff8800000124c8       0      0
 10    4096k  ffff8800000124d8       0      0

ZONE  NAME        SIZE    FREE      MEM_MAP       START_PADDR  START_MAPNR
  1   DMA32     1044480   30117  ffffea0000038000    1000000        4095   
AREA    SIZE  FREE_AREA_STRUCT  BLOCKS  PAGES
  0       4k  ffff88000001a7e8      24     24
  0       4k  ffff88000001a7f8       4      4
  0       4k  ffff88000001a808      13     13
  0       4k  ffff88000001a818       0      0
  0       4k  ffff88000001a828       0      0
  1       8k  ffff88000001a840       2      4
  1       8k  ffff88000001a850       2      4
  1       8k  ffff88000001a860       4      8
  1       8k  ffff88000001a870       0      0
  1       8k  ffff88000001a880       0      0
  2      16k  ffff88000001a898       0      0
  2      16k  ffff88000001a8a8       3     12
  2      16k  ffff88000001a8b8       4     16
  2      16k  ffff88000001a8c8       0      0
  2      16k  ffff88000001a8d8       0      0
  3      32k  ffff88000001a8f0       0      0
  3      32k  ffff88000001a900       3     24
  3      32k  ffff88000001a910       3     24
  3      32k  ffff88000001a920       0      0
  3      32k  ffff88000001a930       0      0
  4      64k  ffff88000001a948       1     16
  4      64k  ffff88000001a958       3     48
  4      64k  ffff88000001a968       6     96
  4      64k  ffff88000001a978       0      0
  4      64k  ffff88000001a988       0      0
  5     128k  ffff88000001a9a0       0      0
  5     128k  ffff88000001a9b0       3     96
  5     128k  ffff88000001a9c0       7    224
  5     128k  ffff88000001a9d0       0      0
  5     128k  ffff88000001a9e0       0      0
  6     256k  ffff88000001a9f8       0      0
  6     256k  ffff88000001aa08       1     64
  6     256k  ffff88000001aa18       6    384
  6     256k  ffff88000001aa28       0      0
  6     256k  ffff88000001aa38       0      0
  7     512k  ffff88000001aa50       1    128
  7     512k  ffff88000001aa60       0      0
  7     512k  ffff88000001aa70       8   1024
  7     512k  ffff88000001aa80       0      0
  7     512k  ffff88000001aa90       0      0
  8    1024k  ffff88000001aaa8       1    256
  8    1024k  ffff88000001aab8       1    256
  8    1024k  ffff88000001aac8       5   1280
  8    1024k  ffff88000001aad8       0      0
  8    1024k  ffff88000001aae8       0      0
  9    2048k  ffff88000001ab00       0      0
  9    2048k  ffff88000001ab10       1    512
  9    2048k  ffff88000001ab20       3   1536
  9    2048k  ffff88000001ab30       1    512
  9    2048k  ffff88000001ab40       0      0
 10    4096k  ffff88000001ab58       0      0
 10    4096k  ffff88000001ab68       0      0
 10    4096k  ffff88000001ab78      22  22528
 10    4096k  ffff88000001ab88       1   1024
 10    4096k  ffff88000001ab98       0      0

ZONE  NAME        SIZE    FREE      MEM_MAP       START_PADDR  START_MAPNR
  2   Normal    7602176   10443  ffffea0003800000   100000000     1048575  
AREA    SIZE  FREE_AREA_STRUCT  BLOCKS  PAGES
  0       4k  ffff880000022ea8     365    365
  0       4k  ffff880000022eb8     274    274
  0       4k  ffff880000022ec8     274    274
  0       4k  ffff880000022ed8       0      0
  0       4k  ffff880000022ee8       0      0
  1       8k  ffff880000022f00      99    198
  1       8k  ffff880000022f10      94    188
  1       8k  ffff880000022f20     360    720
  1       8k  ffff880000022f30       0      0
  1       8k  ffff880000022f40       0      0
  2      16k  ffff880000022f58      30    120
  2      16k  ffff880000022f68      41    164
  2      16k  ffff880000022f78     204    816
  2      16k  ffff880000022f88       0      0
  2      16k  ffff880000022f98       0      0
  3      32k  ffff880000022fb0       9     72
  3      32k  ffff880000022fc0      19    152
  3      32k  ffff880000022fd0     138   1104
  3      32k  ffff880000022fe0       0      0
  3      32k  ffff880000022ff0       0      0
  4      64k  ffff880000023008       7    112
  4      64k  ffff880000023018       4     64
  4      64k  ffff880000023028      77   1232
  4      64k  ffff880000023038       0      0
  4      64k  ffff880000023048       0      0
  5     128k  ffff880000023060       3     96
  5     128k  ffff880000023070       3     96
  5     128k  ffff880000023080      43   1376
  5     128k  ffff880000023090       0      0
  5     128k  ffff8800000230a0       0      0
  6     256k  ffff8800000230b8       0      0
  6     256k  ffff8800000230c8       0      0
  6     256k  ffff8800000230d8      13    832
  6     256k  ffff8800000230e8       0      0
  6     256k  ffff8800000230f8       0      0
  7     512k  ffff880000023110       0      0
  7     512k  ffff880000023120       0      0
  7     512k  ffff880000023130       5    640
  7     512k  ffff880000023140       0      0
  7     512k  ffff880000023150       0      0
  8    1024k  ffff880000023168       0      0
  8    1024k  ffff880000023178       0      0
  8    1024k  ffff880000023188       0      0
  8    1024k  ffff880000023198       0      0
  8    1024k  ffff8800000231a8       0      0
  9    2048k  ffff8800000231c0       0      0
  9    2048k  ffff8800000231d0       0      0
  9    2048k  ffff8800000231e0       1    512
  9    2048k  ffff8800000231f0       0      0
  9    2048k  ffff880000023200       0      0
 10    4096k  ffff880000023218       0      0
 10    4096k  ffff880000023228       0      0
 10    4096k  ffff880000023238       0      0
 10    4096k  ffff880000023248       1   1024
 10    4096k  ffff880000023258       0      0

ZONE  NAME        SIZE    FREE      MEM_MAP       START_PADDR  START_MAPNR
  3   Movable        0       0         0               0            0     

--------------------------------------------------------------------------

NODE
  1
ZONE  NAME        SIZE    FREE      MEM_MAP       START_PADDR  START_MAPNR
  0   DMA            0       0         0               0            0     

ZONE  NAME        SIZE    FREE      MEM_MAP       START_PADDR  START_MAPNR
  1   DMA32          0       0         0               0            0     

ZONE  NAME        SIZE    FREE      MEM_MAP       START_PADDR  START_MAPNR
  2   Normal    8388608   10114  ffffea001ce00000   840000000        0     
AREA    SIZE  FREE_AREA_STRUCT  BLOCKS  PAGES
  0       4k  ffff880840018e28     405    405
  0       4k  ffff880840018e38     162    162
  0       4k  ffff880840018e48     317    317
  0       4k  ffff880840018e58       0      0
  0       4k  ffff880840018e68       0      0
  1       8k  ffff880840018e80     106    212
  1       8k  ffff880840018e90      70    140
  1       8k  ffff880840018ea0     269    538
  1       8k  ffff880840018eb0       0      0
  1       8k  ffff880840018ec0       0      0
  2      16k  ffff880840018ed8      24     96
  2      16k  ffff880840018ee8      18     72
  2      16k  ffff880840018ef8     207    828
  2      16k  ffff880840018f08       0      0
  2      16k  ffff880840018f18       0      0
  3      32k  ffff880840018f30      20    160
  3      32k  ffff880840018f40       4     32
  3      32k  ffff880840018f50     148   1184
  3      32k  ffff880840018f60       0      0
  3      32k  ffff880840018f70       0      0
  4      64k  ffff880840018f88      17    272
  4      64k  ffff880840018f98       2     32
  4      64k  ffff880840018fa8      95   1520
  4      64k  ffff880840018fb8       0      0
  4      64k  ffff880840018fc8       0      0
  5     128k  ffff880840018fe0       4    128
  5     128k  ffff880840018ff0       1     32
  5     128k  ffff880840019000      37   1184
  5     128k  ffff880840019010       0      0
  5     128k  ffff880840019020       0      0
  6     256k  ffff880840019038       0      0
  6     256k  ffff880840019048       0      0
  6     256k  ffff880840019058       8    512
  6     256k  ffff880840019068       0      0
  6     256k  ffff880840019078       0      0
  7     512k  ffff880840019090       0      0
  7     512k  ffff8808400190a0       0      0
  7     512k  ffff8808400190b0       1    128
  7     512k  ffff8808400190c0       0      0
  7     512k  ffff8808400190d0       0      0
  8    1024k  ffff8808400190e8       0      0
  8    1024k  ffff8808400190f8       0      0
  8    1024k  ffff880840019108       1    256
  8    1024k  ffff880840019118       0      0
  8    1024k  ffff880840019128       0      0
  9    2048k  ffff880840019140       0      0
  9    2048k  ffff880840019150       0      0
  9    2048k  ffff880840019160       1    512
  9    2048k  ffff880840019170       1    512
  9    2048k  ffff880840019180       0      0
 10    4096k  ffff880840019198       0      0
 10    4096k  ffff8808400191a8       0      0
 10    4096k  ffff8808400191b8       0      0
 10    4096k  ffff8808400191c8       1   1024
 10    4096k  ffff8808400191d8       0      0

ZONE  NAME        SIZE    FREE      MEM_MAP       START_PADDR  START_MAPNR
  3   Movable        0       0         0               0            0     

nr_free_pages: 54610  (found 54742)

A little exercise with foreach bt

crash> foreach bt | awk '$1 == "#0" { $2 = ""; print }' | sort | uniq -c
     31 #0  crash_nmi_callback at ffffffff81029df6
      1 #0  machine_kexec at ffffffff8103281b
    546 #0  schedule at ffffffff814fda62

Indeed, they are either crashed or waiting for memory (or I am not reading it correctly).

share|improve this question

4 Answers 4

up vote 6 down vote accepted
+150

To check top 20 largest consumer of physical memory (resident set size).

crash> ps -G | sed 's/>//g' | sort -k 8,8 -n | awk '$8 ~ /[0-9]/{ $8 = $8/1024" MB"; print }' | tail -20

To check the number of hugepages.

crash> p -d nr_huge_pages

Update:

A) crash dump was captured from following kernel version.

$ crash --osrelease vmcore.flat 
2.6.32-279.5.2.el6.x86_64                    

B) Lets extract the vmlinux file from kernel-debug-debuginfo package.

$ rpm2cpio kernel-debug-debuginfo-2.6.32-279.5.2.el6.x86_64.rpm | \
  cpio -idv ./usr/lib/debug/lib/modules/*/vmlinux

C) Open vmcore file using crash utility.

$ bunzip2 vmcore.flat.bz2 
$ crash vmcore.flat ./usr/lib/debug/lib/modules/2.6.32-279.5.2.el6.x86_64/vmlinux

D) System Information.

crash> sys
      KERNEL: ./usr/lib/debug/lib/modules/2.6.32-279.5.2.el6.x86_64/vmlinux
    DUMPFILE: vmcore.flat  [PARTIAL DUMP]
        CPUS: 32
        DATE: Tue Feb  5 12:11:52 2013
      UPTIME: 00:04:12
LOAD AVERAGE: 3.03, 0.95, 0.34
       TASKS: 578
    NODENAME: ...
     RELEASE: 2.6.32-279.5.2.el6.x86_64
     VERSION: #1 SMP Fri Aug 24 01:07:11 UTC 2012
     MACHINE: x86_64  (2700 Mhz)
      MEMORY: 64 GB
       PANIC: "[  253.529344] Kernel panic - not syncing: Out of memory and no killable processes..."

a) Panic happened due to Out of memory but "panic_on_oom" parameter is disabled on the system. 

crash> p -d sysctl_panic_on_oom
sysctl_panic_on_oom = $6 = 0

This parameter enables or disables panic on out-of-memory feature. If this is set to 0, the kernel will kill some rogue process, called oom_killer.  Usually, oom_killer can kill rogue processes and system will survive. If this is set to 1, the kernel panics when out-of-memory happens.

b) So, how did we capture the vmcore at the time of oom event?

Well let's check the mm/oom_kill.c source code. It says that if nothing is left on the system to kill then simply hang or panic.

++++++
499         /* Found nothing?!?! Either we hang forever, or we panic. */   
500         if (!p) {                                                  
501             read_unlock(&tasklist_lock);                                     
502             cpuset_unlock();                                        
503             panic("Out of memory and no killable processes...\n");  <<<------  
504         }                                                       
505 
++++++

So we reached to panic state and as kdump service was enabled on this system vmcore was captured.

E) Lets check in kernel ring buffer, 

crash> log
[..]
[  253.351427] Node 0 DMA free:15744kB min:20kB low:24kB high:28kB active_anon:0kB inactive_anon:0kB active_file:0kB inactive_file:0kB unevictable:0kB isolated(anon):0kB isolated(file):0kB present:15356kB mlocked:0kB dirty:0kB writeback:0kB mapped:0kB shmem:0kB slab_reclaimable:0kB slab_unreclaimable:0kB kernel_stack:0kB pagetables:0kB unstable:0kB bounce:0kB writeback_tmp:0kB pages_scanned:0 all_unreclaimable? yes
[  253.352234] lowmem_reserve[]: 0 2955 32245 32245
[  253.352812] Node 0 DMA32 free:120436kB min:4120kB low:5148kB high:6180kB active_anon:0kB inactive_anon:0kB active_file:0kB inactive_file:32kB unevictable:0kB isolated(anon):0kB isolated(file):0kB present:3026080kB mlocked:0kB dirty:0kB writeback:0kB mapped:0kB shmem:0kB slab_reclaimable:20kB slab_unreclaimable:16600kB kernel_stack:0kB pagetables:0kB unstable:0kB bounce:0kB writeback_tmp:0kB pages_scanned:1 all_unreclaimable? no
[  253.353637] lowmem_reserve[]: 0 0 29290 29290
[  253.354216] Node 0 Normal free:40580kB min:40868kB low:51084kB high:61300kB active_anon:956kB inactive_anon:536kB active_file:260kB inactive_file:0kB unevictable:0kB isolated(anon):0kB isolated(file):0kB present:29992960kB mlocked:0kB dirty:0kB writeback:0kB mapped:460kB shmem:136kB slab_reclaimable:3640kB slab_unreclaimable:75128kB kernel_stack:4448kB pagetables:428kB unstable:0kB bounce:0kB writeback_tmp:0kB pages_scanned:0 all_unreclaimable? no
[  253.355047] lowmem_reserve[]: 0 0 0 0
[  253.355624] Node 1 Normal free:39896kB min:45096kB low:56368kB high:67644kB active_anon:412kB inactive_anon:1668kB active_file:288kB inactive_file:0kB unevictable:0kB isolated(anon):0kB isolated(file):220kB present:33095680kB mlocked:0kB dirty:0kB writeback:0kB mapped:92kB shmem:80kB slab_reclaimable:3496kB slab_unreclaimable:87864kB kernel_stack:216kB pagetables:564kB unstable:0kB bounce:0kB writeback_tmp:0kB pages_scanned:0 all_unreclaimable? no
[  253.356457] lowmem_reserve[]: 0 0 0 0
[  253.357034] Node 0 DMA: 2*4kB 1*8kB 1*16kB 1*32kB 1*64kB 0*128kB 1*256kB 0*512kB 1*1024kB 1*2048kB 3*4096kB = 15744kB
[  253.358351] Node 0 DMA32: 41*4kB 8*8kB 7*16kB 6*32kB 10*64kB 10*128kB 7*256kB 9*512kB 7*1024kB 5*2048kB 23*4096kB = 120468kB
[  253.359674] Node 0 Normal: 718*4kB 558*8kB 278*16kB 169*32kB 88*64kB 47*128kB 13*256kB 5*512kB 0*1024kB 1*2048kB 1*4096kB = 40872kB
[  253.360995] Node 1 Normal: 876*4kB 447*8kB 249*16kB 174*32kB 116*64kB 40*128kB 8*256kB 1*512kB 1*1024kB 2*2048kB 1*4096kB = 40952kB
[  253.362319] 154 total pagecache pages
[  253.362502] 0 pages in swap cache
[  253.362684] Swap cache stats: add 0, delete 0, find 0/0
[  253.362869] Free swap  = 0kB
[  253.363050] Total swap = 0kB
[  253.526814] 16777215 pages RAM
[  253.526999] 294628 pages reserved
[  253.527190] 114911 pages shared
[  253.527372] 16392561 pages non-shared
[..]

F) Lets check the memory status on the system at the time of crash.

crash> kmem -i
              PAGES        TOTAL      PERCENTAGE
 TOTAL MEM  16482587      62.9 GB         ----        -------------------------------+
      FREE    54610     213.3 MB    0% of TOTAL MEM                                  |
      USED  16427977      62.7 GB   99% of TOTAL MEM                                 |
    SHARED     4683      18.3 MB    0% of TOTAL MEM                                  |
   BUFFERS      118       472 KB    0% of TOTAL MEM                                  |
    CACHED       82       328 KB    0% of TOTAL MEM                                  |
      SLAB    46635     182.2 MB    0% of TOTAL MEM                                  |
                                                                                     |
TOTAL SWAP        0            0         ----         ----------------------+        |
 SWAP USED        0            0  100% of TOTAL SWAP                        |        |
 SWAP FREE        0            0    0% of TOTAL SWAP                        |        |
                                                                            |        | 
                                                                            |        |
crash> p -d totalram_pages                                                  |        |
totalram_pages = $5 = 16482587                                              |        |
                                                                            |        |
crash> !echo "scale=5;(16482587*4096)/2^30"|bc -q                           |        |
62.87607                  <<<-----[ Total physical memory is 62.9 GB ] <<<--|--------+
                                                                            |
crash> p -d total_swap_pages                                                |
total_swap_pages = $6 = 0 <<<------[ No Swap on the system ]  <<<-----------+
  • We have total ~63GiB of Physical Memory.
  • Swap partition or file is not created on the system, so we don't have swap on this server.
  • Memory used for cache is very less 328KB and for buffer it's 472KB.
  • Memory used in slab is also very less only 182.2 MB.

G) The total memory allocated to process(es) is 0.00391006GiB.

crash> ps -G | tail -n +2 | cut -b2- | gawk '{mem += $8} END {print "total " mem/1048576 "GB"}'
total 0.00391006GB

H) The application process(es) are not utilizing memory on the system. 

crash> ps -G | sed 's/>//g' | sort -k 8,8 -n | awk '$8 ~ /[0-9]/{ $8 = $8/1024" MB"; print }' | tail -20
965 2 21 ffff8808292f1500 IN 0.0 0 0 MB [ext4-dio-unwrit]
966 2 22 ffff8808292d4080 IN 0.0 0 0 MB [ext4-dio-unwrit]
967 2 23 ffff8808292ce040 IN 0.0 0 0 MB [ext4-dio-unwrit]
968 2 24 ffff8808299b5540 IN 0.0 0 0 MB [ext4-dio-unwrit]
969 2 25 ffff880829aa6040 IN 0.0 0 0 MB [ext4-dio-unwrit]
970 2 26 ffff880827367500 IN 0.0 0 0 MB [ext4-dio-unwrit]
971 2 27 ffff880827366aa0 IN 0.0 0 0 MB [ext4-dio-unwrit]
972 2 28 ffff880827366040 IN 0.0 0 0 MB [ext4-dio-unwrit]
97 2 23 ffff88082c1ac080 IN 0.0 0 0 MB [ksoftirqd/23]
973 2 29 ffff880827371540 IN 0.0 0 0 MB [ext4-dio-unwrit]
974 2 30 ffff880827370ae0 IN 0.0 0 0 MB [ext4-dio-unwrit]
975 2 31 ffff880827370080 IN 0.0 0 0 MB [ext4-dio-unwrit]
98 2 23 ffff88082c1bb500 IN 0.0 0 0 MB [watchdog/23]
99 2 24 ffff88082c1baaa0 IN 0.0 0 0 MB [migration/24]
3171 1 3 ffff880826ccaaa0 IN 0.0 27636 0.234375 MB auditd
1 0 1 ffff88082c41b500 UN 0.0 19348 0.339844 MB init
3772 1 0 ffff88102b257500 RU 0.0 64072 0.652344 MB sshd
1047 1 2 ffff881029524040 IN 0.0 11188 0.925781 MB udevd
4936 1047 4 ffff880ff342d540 IN 0.0 11184 0.925781 MB udevd
4937 1047 5 ffff88082a240080 IN 0.0 11184 0.925781 MB udevd

I) Let's verify the memory tuning parameters on the system.

crash> p -d sysctl_overcommit_memory
sysctl_overcommit_memory = $7 = 0

This value contains a flag that enables memory overcommitment. When this flag is 0, the kernel attempts to estimate the amount of free memory left when userspace requests more memory.

crash> p -d sysctl_overcommit_ratio
sysctl_overcommit_ratio = $8 = 50

When overcommit_memory is set to 2, the committed address space is not permitted to exceed swap plus this percentage of physical RAM. 

crash> p -d zone_reclaim_mode 
zone_reclaim_mode = $4 = 0

Zone_reclaim_mode allows someone to set more or less aggressive approaches to reclaim memory when a zone runs out of memory. If it is set to zero then no zone reclaim occurs.

crash> p -d min_free_kbytes
min_free_kbytes = $3 = 90112  <<<--------[ 88 MB ]

The minimum number of kilobytes to keep free across the system. This value is used to compute a watermark value for each low memory zone, which are then assigned a number of reserved free pages proportional to their size. When setting this parameter, as both too-low and too-high values can be damaging.

In other words, setting min_free_kbytes too low prevents the system from reclaiming memory. This can result in system hangs and OOM-killing multiple processes. However, setting this parameter to a value that is too high (5-10% of total system memory) will cause your system to become out-of-memory immediately. Linux is designed to use all available RAM to cache file system data. Setting a high min_free_kbytes value results in the system spending too much time reclaiming memory. 

The values of above parameters looks okay, So where is my memory ???

Assumptions:

  1. The main offender(s) is not in user-space. Based on my experience the unaccountable memory is due to Mellanox and DRBD modules but I am not sure in your case. 
  2. As most of the pages are discarded from vmcore file in order to reduce the size of vmcore file ( core_collector makedumpfile -d 31 -c ). I am unable to check hugepage size.  
share|improve this answer
    
ps displays almost no processes as occupying any memory. In fact, ps -G shows only five entries where the RSS is non-zero, and the sum of those numbers is 4100 (see the ps -u output in the question). The second command says No symbol "nr_huge_pages" in current context.. –  chutz Feb 13 '13 at 16:06
    
If possible can you share your vmcore file so that I can do a deep dive ? I will post my findings and exact steps here.. :) –  BKS Feb 14 '13 at 13:58
    
tmpfs is anonymously backed -- is it possible to check page allocation for tmpfs in crash? –  Matthew Ife Feb 21 '13 at 1:05
    
For those who love and want to play with crash: people.redhat.com/anderson/.crash_whitepaper –  BKS Feb 25 '13 at 15:42

Can you run this command.

ps -G | tail -n +2 | cut -b2- | gawk '{mem += $8} END {Print "total " mem/1048576 "GB"}'

Also, kmem -z and kmem -f might help.

However, see that the entire swap space is consumed.

You must have got some OOM messages in the log command. Can you pastebin the OOM messages. I can see the mode and race condition too.

On other note, a sys output will help immensely. You know, memory leak and kernel upgrades are almost synonymous ;)

EDIT: Try this yourself. foreach bt

It will show the trace for each PID. Look for any common pattern, could be all of them are waiting for the schedule_at function. Meaning something waiting for memory allocation.

Now, note the value of TASK in the section which shows each PID in foreach bt.

Run this.

tasK_struct.tgid <TASK>

If they are from same PID, the processes you are seeing are threaded.

I forgot how to check for the overcommit value, I will see if I can find out.

share|improve this answer
    
Thanks. I updated the question with some of the info you say may be useful. Note about the swap space - it is not all consumed, there is simply no swap configured. Also note that almost all the userland processes are dead at the time of the crash (the OOM killer took care of that). I even pasted the almost complete (pastebin only lets me upload 500K) output of "log -m" - pastebin.com/BzvqdyyZ. –  chutz Feb 8 '13 at 1:23

I do not have much experrience with analysing crash dump and therfore not able to help you with some specific advice, but here are some links which I have collected and used from time to time. Maybe you will find there something usefull:

share|improve this answer
    
Well, I've done all this. I am able to run crash, and the Crash book mentions the bt command (which I already ran), the log command, which showed me the Out of memory messages, and the ps command which doesn't tell me where my memory is :( –  chutz Feb 6 '13 at 1:26

You may know this and have simply not indicated this is what you did, but, there's lots of options to ps.

# ps aux

or

# ps -edf 

as root will spit much more detailed information.

There's a great deal of helpful suggestions on this page to help track down memory issues:

http://www.linuxnix.com/2011/05/find-ram-utilization-user-linux.html

I'd check

# free

periodically to see how much memory is actually being used. (Or better yet, have it graphed; graphite or munin are great for this) so that you can visualize when/how your memory is being used.

64 gigs of ram is quite a bit; what sort of work does the host do?

share|improve this answer
1  
What I posted is the output of the ps subcommand of crash. It is not the ps shell command. I am doing a post-mortem of the incident, and all I have is the vmcore image. I can only assume I should be able to see where all that memory is allocated. –  chutz Feb 6 '13 at 1:21

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