Re: OOM problems

[John Weekes <lists.xen@nuclearfallout.net>]

 > What do the guests use for storage? (e.g. "blktap2 for VHD files on 
an iscsi mounted ext3 volume")

Simple sparse .img files on a local ext4 RAID volume, using "file:".

 > It might be worth looking at /proc/kernel/slabinfo to see if there's 
anything suspicious.

I didn't see anything suspicious in there, but I'm not sure what I'm 
looking for.

Here is the first page of slabtop as it currently stands, if that helps. 
It looks a bit easier to read.

  Active / Total Objects (% used)    : 274753 / 507903 (54.1%)
  Active / Total Slabs (% used)      : 27573 / 27582 (100.0%)
  Active / Total Caches (% used)     : 85 / 160 (53.1%)
  Active / Total Size (% used)       : 75385.52K / 107127.41K (70.4%)
  Minimum / Average / Maximum Object : 0.02K / 0.21K / 4096.00K

   OBJS ACTIVE  USE OBJ SIZE  SLABS OBJ/SLAB CACHE SIZE NAME
306397 110621  36%    0.10K   8281       37     33124K buffer_head
  37324  26606  71%    0.54K   5332        7     21328K radix_tree_node
  25640  25517  99%    0.19K   1282       20      5128K size-192
  23472  23155  98%    0.08K    489       48      1956K sysfs_dir_cache
  19964  19186  96%    0.95K   4991        4     19964K ext4_inode_cache
  17860  13026  72%    0.19K    893       20      3572K dentry
  14896  13057  87%    0.03K    133      112       532K size-32
   8316   6171  74%    0.17K    378       22      1512K vm_area_struct
   8142   5053  62%    0.06K    138       59       552K size-64
   4320   3389  78%    0.12K    144       30       576K size-128
   3760   2226  59%    0.19K    188       20       752K filp
   3456   1875  54%    0.02K     24      144        96K anon_vma
   3380   3001  88%    1.00K    845        4      3380K size-1024
   3380   3365  99%    0.76K    676        5      2704K shmem_inode_cache
   2736   2484  90%    0.50K    342        8      1368K size-512
   2597   2507  96%    0.07K     49       53       196K Acpi-Operand
   2100   1095  52%    0.25K    140       15       560K skbuff_head_cache
   1920    819  42%    0.12K     64       30       256K cred_jar
   1361   1356  99%    4.00K   1361        1      5444K size-4096
   1230    628  51%    0.12K     41       30       164K pid
   1008    907  89%    0.03K      9      112        36K Acpi-Namespace
    959    496  51%    0.57K    137        7       548K inode_cache
    891    554  62%    0.81K     99        9       792K signal_cache
    888    115  12%    0.10K     24       37        96K ext4_prealloc_space
    885    122  13%    0.06K     15       59        60K fs_cache
    850    642  75%    1.45K    170        5      1360K task_struct
    820    769  93%    0.19K     41       20       164K bio-0
    666    550  82%    2.06K    222        3      1776K sighand_cache
    576    211  36%    0.50K     72        8       288K task_xstate
    529    379  71%    0.16K     23       23        92K cfq_queue
    518    472  91%    2.00K    259        2      1036K size-2048
    506    375  74%    0.16K     22       23        88K cfq_io_context
    495    353  71%    0.33K     45       11       180K blkdev_requests
    465    422  90%    0.25K     31       15       124K size-256
    418    123  29%    0.69K     38       11       304K files_cache
    360    207  57%    0.69K     72        5       288K sock_inode_cache
    360    251  69%    0.12K     12       30        48K scsi_sense_cache
    336    115  34%    0.08K      7       48        28K blkdev_ioc
    285    236  82%    0.25K     19       15        76K scsi_cmd_cache


 > BTW: 24 vCPUs in dom0 seems a excessive, especially if you're using 
stubdoms. You may get better performance by dropping that to e.g. 2 or 3.

I will test that. Do you think it will make a difference in this case?

-John