[NiteWave]

pstree -p | grep litespeed
|-litespeed(20208)-+-httpd(20209)
| `-litespeed(20210)-+-lsphp5(1343)---sh(5522)---convert(5523)

APC or xcache is associated with a lsphp5 process(or a group of processes:a parent process, a few child processes). in example of above case, it's lsphp5 which pid=1343. if in some reason, this process is killed and a new lsphp5 process is started by its parent litespeed(in above example, pid=20210), then you'll notice opcode cache is cleared.

so monitor lsphp5's pid at the same time while monitoring the cache hits number. if the pid changes, the issue is turned to be how to keep it longer and what's reason it's killed and restarted again.