Find the process

top

  PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND
12399 root      20   0  120m 3040 1316 R 100.0  0.1  21488:30 perl
 1083 root      20   0 10404  728  644 R 98.7  0.0  23601:08 libcrypto.b

ps aux | grep

Find the process

root     12399 99.9  0.0 123316  3040 ?        R    Feb05 21490:06 perl -n -e /\b\S+\@(btinternet).\S+\b/ && print $&,"\n";  /var/lib/yum/yumdb/c/fcb244c0a5e60a026aed0bc937e76c6b01b4

Note the time

Feb05 21490:06 

Time is in minutes

ps -eo pid,etime | awk '/^12399/ {print $2}'
14-22:24:24

14 days, 22 hours, 24 minutes