My limits.conf file: ----------------------- # /etc/security/limits.conf * hard core 0 * hard rss 153600 ----------------------- ulimit -a output: ----------------------- core file size (blocks, -c) 0 data seg size (kbytes, -d) unlimited file size (blocks, -f) unlimited max locked memory (kbytes, -l) unlimited max memory size (kbytes, -m) 153600 open files (-n) 1024 pipe size (512 bytes, -p) 8 stack size (kbytes, -s) 8192 cpu time (seconds, -t) unlimited max user processes (-u) 2047 virtual memory (kbytes, -v) unlimited ----------------------- When i run perl -e '$a= "a" x (1024*1024*151); sleep 30;' ps u -a in other console gives: ----------------------- USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND antony 13494 14.3 71.4 315712 183496 pts/0 D 14:53 0:03 perl -e $a= "a" x antony 13501 0.0 0.2 2692 736 pts/1 R 14:53 0:00 ps u -a ----------------------- perl process consumes more memory than specified in limits.conf software versions: Red Had 9 glibc-2.3.2-27.9 compiled from updates srpm kernel 2.4.21 compiled from kernel.org source