The patch below reduces kernel memory used by SELinux policy rules by about
37% on 64-bit systems.  This is because the size of struct avtab_node is 40
bytes on 64-bit, and defaults to a size-64 slab.

Creating a slab cache specifically for these structs saves considerable
amounts of kernel memory on 64-bit systems with large rulesets.  'Strict'
policy has over 300k rules, while 'targeted' policy has around 3k rules.

Here's the slabtop output with 64 and 40 byte sized slabs to show the
memory savings, for strict policy:

303475 303447  99%    0.06K   4975       61     19900K avtab_node 
303456 303447  99%    0.04K   3161       96     12644K avtab_node

Also, there are 57% more objects per slab.
Signed-off-by: James Morris <jmorris@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>