> Server -> Security -> External Application Resources
for "ideal Process Soft Limit, and Hard Limit", default one is good for most cases.
for example lsphp5, you can
pstree -p|grep lsphp5 |wc
to know how many lsphp5 are running on your server.
you can set the limit big enough, say 1000,2000, i.e., almost no limit, see if your system load is too high.