From: Chengming Zhou <zhouchengming@xxxxxxxxxxxxx> The current updated scheme (which this series implemented) is: - node partial slabs: PG_Workingset && !frozen - cpu partial slabs: !PG_Workingset && !frozen - cpu slabs: !PG_Workingset && frozen - full slabs: !PG_Workingset && !frozen The most important change is that "frozen" bit is not set for the cpu partial slabs anymore, __slab_free() will grab node list_lock then check by !PG_Workingset that it's not on a node partial list. And the "frozen" bit is still kept for the cpu slabs for performance, since we don't need to grab node list_lock to check whether the PG_Workingset is set or not if the "frozen" bit is set in __slab_free(). Update related documentations and comments in the source. Signed-off-by: Chengming Zhou <zhouchengming@xxxxxxxxxxxxx> Tested-by: Hyeonggon Yoo <42.hyeyoo@xxxxxxxxx> --- mm/slub.c | 16 ++++++++++++---- 1 file changed, 12 insertions(+), 4 deletions(-) diff --git a/mm/slub.c b/mm/slub.c index c20bdf5dab0f..a307d319e82c 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -76,13 +76,22 @@ * * Frozen slabs * - * If a slab is frozen then it is exempt from list management. It is not - * on any list except per cpu partial list. The processor that froze the + * If a slab is frozen then it is exempt from list management. It is + * the cpu slab which is actively allocated from by the processor that + * froze it and it is not on any list. The processor that froze the * slab is the one who can perform list operations on the slab. Other * processors may put objects onto the freelist but the processor that * froze the slab is the only one that can retrieve the objects from the * slab's freelist. * + * CPU partial slabs + * + * The partially empty slabs cached on the CPU partial list are used + * for performance reasons, which speeds up the allocation process. + * These slabs are not frozen, but are also exempt from list management, + * by clearing the PG_workingset flag when moving out of the node + * partial list. Please see __slab_free() for more details. + * * list_lock * * The list_lock protects the partial and full list on each node and @@ -2617,8 +2626,7 @@ static void put_partials_cpu(struct kmem_cache *s, } /* - * Put a slab that was just frozen (in __slab_free|get_partial_node) into a - * partial slab slot if available. + * Put a slab into a partial slab slot if available. * * If we did not find a slot then simply move all the partials to the * per node partial list. -- 2.20.1
