This change is primarily an attempt to make it easier to realize the optimizations the compiler performs in-case CONFIG_MEMCG_KMEM is not enabled. Performance wise, even when CONFIG_MEMCG_KMEM is compiled in, the overhead is zero. This is because, as long as no process have enabled kmem cgroups accounting, the assignment is replaced by asm-NOP operations. This is possible because memcg_kmem_enabled() uses a static_key_false() construct. It also helps readability as it avoid accessing the p[] array like: p[size - 1] which "expose" that the array is processed backwards inside helper function build_detached_freelist(). Lastly this also makes the code more robust, in error case like passing NULL pointers in the array. Which were previously handled before commit 033745189b1b ("slub: add missing kmem cgroup support to kmem_cache_free_bulk"). Fixes: 033745189b1b ("slub: add missing kmem cgroup support to kmem_cache_free_bulk") Signed-off-by: Jesper Dangaard Brouer <brouer@xxxxxxxxxx> --- V2: used Joonsoo Kim's suggestion to store "s" in struct detached_freelist. - Suggested-by: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx> - Verified ASM code generated is still optimal, with different ifdef config's mm/slub.c | 22 +++++++++++----------- 1 file changed, 11 insertions(+), 11 deletions(-) diff --git a/mm/slub.c b/mm/slub.c index 46997517406e..65d5f92d51d2 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -2819,6 +2819,7 @@ struct detached_freelist { void *tail; void *freelist; int cnt; + struct kmem_cache *s; }; /* @@ -2833,8 +2834,9 @@ struct detached_freelist { * synchronization primitive. Look ahead in the array is limited due * to performance reasons. */ -static int build_detached_freelist(struct kmem_cache *s, size_t size, - void **p, struct detached_freelist *df) +static inline +int build_detached_freelist(struct kmem_cache *s, size_t size, + void **p, struct detached_freelist *df) { size_t first_skipped_index = 0; int lookahead = 3; @@ -2850,8 +2852,11 @@ static int build_detached_freelist(struct kmem_cache *s, size_t size, if (!object) return 0; + /* Support for memcg, compiler can optimize this out */ + df->s = cache_from_obj(s, object); + /* Start new detached freelist */ - set_freepointer(s, object, NULL); + set_freepointer(df->s, object, NULL); df->page = virt_to_head_page(object); df->tail = object; df->freelist = object; @@ -2866,7 +2871,7 @@ static int build_detached_freelist(struct kmem_cache *s, size_t size, /* df->page is always set at this point */ if (df->page == virt_to_head_page(object)) { /* Opportunity build freelist */ - set_freepointer(s, object, df->freelist); + set_freepointer(df->s, object, df->freelist); df->freelist = object; df->cnt++; p[size] = NULL; /* mark object processed */ @@ -2885,25 +2890,20 @@ static int build_detached_freelist(struct kmem_cache *s, size_t size, return first_skipped_index; } - /* Note that interrupts must be enabled when calling this function. */ -void kmem_cache_free_bulk(struct kmem_cache *orig_s, size_t size, void **p) +void kmem_cache_free_bulk(struct kmem_cache *s, size_t size, void **p) { if (WARN_ON(!size)) return; do { struct detached_freelist df; - struct kmem_cache *s; - - /* Support for memcg */ - s = cache_from_obj(orig_s, p[size - 1]); size = build_detached_freelist(s, size, p, &df); if (unlikely(!df.page)) continue; - slab_free(s, df.page, df.freelist, df.tail, df.cnt, _RET_IP_); + slab_free(df.s, df.page, df.freelist, df.tail, df.cnt,_RET_IP_); } while (likely(size)); } EXPORT_SYMBOL(kmem_cache_free_bulk); -- 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>