title: APC: opcode cache vs. user cache - set separate limits
body: <p>I am trying to move from the typical combination of APC (for opcode) and Memcache (for my userdata) to a purely apc based cache.  Given my usage structure it makes sense and performance is higher. </p>
  
  <p>But unlike before, where the apc cache was limited to a reasonable size and did not affect my data cache, I am now worried that the opcode cache might grow relatively large so that the sum of opcode cache an datacache exceeds the limit.  As far as I understand, this would result in a flush of the total cache.</p>
  
  <p>Is there a way to mimic the behaviour, as if apc was only an opcode cache and limit the opcode cache size to a reasonable limit, leaving the rest for user data?</p>
  
  <p>Or should I try setting lower ttl values for the opcode cache, so it always gets flushed first?</p>