This patchset does some clean-up and tries to remove lockdep annotation. Patches 1~3 are just for really really minor improvement. Patches 4~9 are for clean-up and removing lockdep annotation. There are two cases that lockdep annotation is needed in SLAB. 1) holding two node locks 2) holding two array cache(alien cache) locks I looked at the code and found that we can avoid these cases without any negative effect. 1) occurs if freeing object makes new free slab and we decide to destroy it. Although we don't need to hold the lock during destroying a slab, current code do that. Destroying a slab without holding the lock would help the reduction of the lock contention. To do it, I change the implementation that new free slab is destroyed after releasing the lock. 2) occurs on similar situation. When we free object from non-local node, we put this object to alien cache with holding the alien cache lock. If alien cache is full, we try to flush alien cache to proper node cache, and, in this time, new free slab could be made. Destroying it would be started and we will free metadata object which comes from another node. In this case, we need another node's alien cache lock to free object. This forces us to hold two array cache locks and then we need lockdep annotation although they are always different locks and deadlock cannot be possible. To prevent this situation, I use same way as 1). In this way, we can avoid 1) and 2) cases, and then, can remove lockdep annotation. As short stat noted, this makes SLAB code much simpler. This patchset is based on slab/next branch on Pekka's git tree. git://git.kernel.org/pub/scm/linux/kernel/git/penberg/linux.git Thanks. Joonsoo Kim (9): slab: add unlikely macro to help compiler slab: makes clear_obj_pfmemalloc() just return store masked value slab: move up code to get kmem_cache_node in free_block() slab: defer slab_destroy in free_block() slab: factor out initialization of arracy cache slab: introduce alien_cache slab: use the lock on alien_cache, instead of the lock on array_cache slab: destroy a slab without holding any alien cache lock slab: remove a useless lockdep annotation mm/slab.c | 384 ++++++++++++++++++++++--------------------------------------- mm/slab.h | 2 +- 2 files changed, 138 insertions(+), 248 deletions(-) -- 1.7.9.5 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
