Is there a specific reason why you're doing this? (I'd guess there is...) Load will immediately go up after doing this because you've dropped Linux's caches (which it should generally be pretty good at managing itself), the machine has to work harder without these caches in place until they've been rebuilt.
In the case of cPanel servers, having instances or machines completely run out of memory (provided the server simply isn't too small ram wise for what you're running) is generally an indication something is going awry with a site / user account and it's scripting, or that you need to make a decision about how for example php runs or how to mitigate heavy usage / an attack.