[Users] OOM and /etc/vz/oom-groups.conf

[Mark J.]

Hello,

I have been trying to tweak the OOM killer to prevent some database corruption thats been happening in the VM's when the oom killer kills off mysql. Based on what i have read online and in the conf file itself I am a bit confused on why its not killing other things off before mysql.

Based on the following (taken directly form the conf file):

OOM-score adjustment, a number from -1000 to 1000. A positive number increases the chances of killing, while a negative number decreases it (more protection). -1000 makes a process unkillable till any other process exists.

I made the following changes to the conf file:

mysqld          init            -500    -1000
httpd           init            -500    100
httpsd          init            -500    100
apache          init            -500    100
php             init            -500    100


Saved and then made the changes live:

cat /etc/vz/oom-groups.conf > /proc/vz/oom_score_adj


Verified the changes were in fact live:

root ~ #cat /proc/vz/oom_score_adj | grep mysql
mysqld init -500 -1000
root ~ #cat /proc/vz/oom_score_adj | grep http
httpd init -500 100
httpsd init -500 100


However I am still watching mysql get killed off before anything else:

Oct  1 14:38:18 server kernel: [2456651.082410] >>> 3679 oom generation 62 starts
Oct  1 14:38:18 server kernel: [2456651.082418] 133199 (mysqld) invoked loc oom-killer: gfp 0x200da order 0 oomkilladj=0
Oct  1 14:38:18 server kernel: [2456651.084483] Out of memory in UB: Kill process 126607 (mysqld) score -903 or sacrifice child
Oct  1 14:38:18 server kernel: [2456651.084772] OOM killed process 126607 (mysqld) vm:3829812kB, rss:166344kB, swap:36760kB
Oct  1 14:38:18 server kernel: [2456651.115460] OOM killed process mysqld (pid=157305, ve=3679) exited, free=519316.
Oct  1 14:38:18 server kernel: [2456651.115465] <<< 3679 oom generation 62 ends (task died)

Anyone have any suggestions or been able to make these adjustments that worked? Any help would be of great assistance.