what is core file size?
and resident set size?
and stack size?
A core file is a dump of memory to disk, used for debugging problems. The limit on the core file size specifies how much memory to dump. If you don't want "core" files, you can set the limit to 0.
The resident set is the number of pages that that are actually in memory (as opposed to being on swap - non-resident). Limiting the resident size will allow more users to use the system, but will also degrade performance and increase swapping.
The stack is an area of memory used by programs to hold intermediate results and subroutine return information. More details here
. If you set the stack size smaller than needed by a program, it will fail.