I saw three copies of a process running and one of them cored in what seems like memory issue. Each individually occupies about 3-4 GB of memory..would a limit account for killing one of them? And if this was the case which one would be killed?
2 Answers
They are per process but can be user dependent, and actually the config calls it domain specific.
example, I set following limits so that I could process audio with better latency, and I am a member of the audio group. So it only affects my processes.
@audio - rtprio 100 @audio - nice -10 It also depends on the limit which is being set. maxlogins, nprocs are obviously per user. on the other hand core is a per process limit.
<domain> can be: # - an user name # - a group name, with @group syntax # - the wildcard *, for default entry # - the wildcard %, can be also used with %group syntax, # for maxlogin limit # - NOTE: group and wildcard limits are not applied to root. # To apply a limit to the root user, <domain> must be # the literal username root. # 
Refering man 5 limits.conf
The pam_limits.so module applies ulimit limits, nice priority and number of simultaneous login sessions limit to user login sessions. The syntax of the lines is as follows: <domain><type><item><value> <domain> = a username, a groupname, the wildcard *, the wildcard %, an uid range, a gid range, a gid specified as %:<gid> applicable to maxlogins limit only
/var/log/syslogor/var/log/messagesif you have it. In particular, look foroom-killerlines in those logs.