mm/slab: introduce new freed objects management way, OBJFREELIST_SLAB

From: Joonsoo Kim <iamjoonsoo.kim@lge.com>

This submission is just intended to get more review if possible.
This patchset is already on mmotm for a month and there is
no problem at all. No changes from mmotm one.

Changes from v1:
o Fold fixes into corresponding ones (no difference from mmotm)
o Add a clean-up patch at last per Christoph's comment

Hello,

This patchset implements new freed object management way, that is,
OBJFREELIST_SLAB. Purpose of it is to reduce memory overhead in SLAB.

SLAB needs a array to manage freed objects in a slab. If there is
leftover after objects are packed into a slab, we can use it as
a management array, and, in this case, there is no memory waste.
But, in the other cases, we need to allocate extra memory for
a management array or utilize dedicated internal memory in a slab for it.
Both cases causes memory waste so it's not good.

With this patchset, freed object itself can be used for a management
array. So, memory waste could be reduced. Detailed idea and numbers
are described in last patch's commit description. Please refer it.

Thanks.

Joonsoo Kim (17):
  mm/slab: fix stale code comment
  mm/slab: remove useless structure define
  mm/slab: remove the checks for slab implementation bug
  mm/slab: activate debug_pagealloc in SLAB when it is actually enabled
  mm/slab: use more appropriate condition check for debug_pagealloc
  mm/slab: clean up DEBUG_PAGEALLOC processing code
  mm/slab: alternative implementation for DEBUG_SLAB_LEAK
  mm/slab: remove object status buffer for DEBUG_SLAB_LEAK
  mm/slab: put the freelist at the end of slab page
  mm/slab: align cache size first before determination of OFF_SLAB
    candidate
  mm/slab: clean up cache type determination
  mm/slab: do not change cache size if debug pagealloc isn't possible
  mm/slab: make criteria for off slab determination robust and simple
  mm/slab: factor out slab list fixup code
  mm/slab: factor out debugging initialization in cache_init_objs()
  mm/slab: introduce new slab management type, OBJFREELIST_SLAB
  mm/slab: avoid returning values by reference

 include/linux/mm.h       |  12 +-
 include/linux/slab_def.h |   3 +
 mm/slab.c                | 626 ++++++++++++++++++++++++++---------------------
 3 files changed, 362 insertions(+), 279 deletions(-)

-- 
1.9.1