[PATCH v3 0/7] mm: Use slab_list list_head instead of lru

Tobin C. Harding
2019-03-14T05:32:10Z

Currently the slab allocators (ab)use the struct page 'lru' list_head.
We have a list head for slab allocators to use, 'slab_list'.

During v2 it was noted by Christoph that the SLOB allocator was reaching
into a list_head, this version adds 2 patches to the front of the set to
fix that.

Clean up all three allocators by using the 'slab_list' list_head instead
of overloading the 'lru' list_head.

Patch 1 - Adds a function to rotate a list to a specified entry.

Patch 2 - Removes the code that reaches into list_head and instead uses
the list_head API including the newly defined function.

Patches 3-7 are unchanged from v3

Patch 3 (v2: patch 4) - Changes the SLOB allocator to use slab_list
instead of lru.

Patch 4 (v2: patch 1) - Makes no code changes, adds comments to #endif
statements.

Patch 5 (v2: patch 2) - Use slab_list instead of lru for SLUB allocator.

Patch 6 (v2: patch 3) - Use slab_list instead of lru for SLAB allocator.

Patch 7 (v2: patch 5) - Removes the now stale comment in the page struct
definition.

During v2 development patches were checked to see if the object file
before and after was identical. Clearly this will no longer be possible
for mm/slob.o, however this work is still of use to validate the
change from lru -> slab_list.

Patch 1 was tested with a module (creates and populates a list then
calls list_rotate_to_front() and verifies new order):

https://github.com/tcharding/ktest/tree/master/list_head

Patch 2 was tested with another module that does some basic slab
allocation and freeing to a newly created slab cache:

https://github.com/tcharding/ktest/tree/master/slab

Tested on a kernel with this in the config:

CONFIG_SLOB=y
CONFIG_SLAB_MERGE_DEFAULT=y

Changes since v2:

- Add list_rotate_to_front().
- Fix slob to use list_head API.
- Re-order patches to put the list.h changes up front.
- Add acks from Christoph.

Changes since v1:

- Verify object files are the same before and after the patch set is
applied (suggested by Matthew).
- Add extra explanation to the commit logs explaining why these changes
are safe to make (suggested by Roman).
- Remove stale comment (thanks Willy).

thanks,
Tobin.

Tobin C. Harding (7):
list: Add function list_rotate_to_front()
slob: Respect list_head abstraction layer
slob: Use slab_list instead of lru
slub: Add comments to endif pre-processor macros
slub: Use slab_list instead of lru
slab: Use slab_list instead of lru
mm: Remove stale comment from page struct

include/linux/list.h | 18 ++++++++++++
include/linux/mm_types.h | 2 +-
mm/slab.c | 49 ++++++++++++++++----------------
mm/slob.c | 32 +++++++++++++--------
mm/slub.c | 60 ++++++++++++++++++++--------------------
5 files changed, 94 insertions(+), 67 deletions(-)

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2.21.0