I'd like clarification on whether or not Linux slab memory will be freed (or mostly freed) if userspace programs need it.
I've noticed that one of my Linux systems had a large amount of memory allocated to "slab":
(from slabtop)
OBJS ACTIVE USE OBJ SIZE SLABS OBJ/SLAB CACHE SIZE NAME
834768 834766 99% 0.94K 24552 34 785664K ext4_inode_cache
694092 354151 51% 0.19K 33052 21 132208K dentry
I realize I can clear it out manually if I want to with (sync; echo 3 > /proc/sys/vm/drop_caches) but do I need to or will Linux free it on it's own when needed?