slab, slub: remove size disparity on debug kernel

I have noticed on debug kernel with SLAB, the size of some non-root
slabs were larger than their corresponding root slabs.

e.g. for radix_tree_node:
  $cat /proc/slabinfo | grep radix
  name     <active_objs> <num_objs> <objsize> <objperslab> <pagesperslab> ...
  radix_tree_node 15052    15075      4096         1             1 ...

  $cat /cgroup/memory/temp/memory.kmem.slabinfo | grep radix
  name     <active_objs> <num_objs> <objsize> <objperslab> <pagesperslab> ...
  radix_tree_node 1581      158       4120         1             2 ...

However for SLUB in debug kernel, the sizes were same.  On further
inspection it is found that SLUB always use kmem_cache.object_size to
measure the kmem_cache.size while SLAB use the given kmem_cache.size.
In the debug kernel the slab's size can be larger than its object_size.
Thus in the creation of non-root slab, the SLAB uses the root's size as
base to calculate the non-root slab's size and thus non-root slab's size
can be larger than the root slab's size.  For SLUB, the non-root slab's
size is measured based on the root's object_size and thus the size will
remain same for root and non-root slab.

This patch makes slab's object_size the default base to measure the
slab's size.

Link: http://lkml.kernel.org/r/[email protected]
Fixes: 794b1248be4e ("memcg, slab: separate memcg vs root cache creation paths")
Signed-off-by: Shakeel Butt <[email protected]>
Cc: Christoph Lameter <[email protected]>
Cc: Pekka Enberg <[email protected]>
Cc: David Rientjes <[email protected]>
Cc: Joonsoo Kim <[email protected]>
Cc: Vladimir Davydov <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

0 files changed, 0 insertions, 0 deletions