From: Chengming Zhou zhouchengming@bytedance.com
mainline inclusion from mainline-v6.8-rc1 commit 8cd3fa428b56352beaa38df756c1d3f1556f5514 category: performance bugzilla: https://gitee.com/openeuler/kernel/issues/I9CSFJ CVE: NA
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i...
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Now we will freeze slabs when moving them out of node partial list to cpu partial list, this method needs two cmpxchg_double operations:
1. freeze slab (acquire_slab()) under the node list_lock 2. get_freelist() when pick used in ___slab_alloc()
Actually we don't need to freeze when moving slabs out of node partial list, we can delay freezing to when use slab freelist in ___slab_alloc(), so we can save one cmpxchg_double().
And there are other good points: - The moving of slabs between node partial list and cpu partial list becomes simpler, since we don't need to freeze or unfreeze at all.
- The node list_lock contention would be less, since we don't need to freeze any slab under the node list_lock.
We can achieve this because there is no concurrent path would manipulate the partial slab list except the __slab_free() path, which is now serialized by slab_test_node_partial() under the list_lock.
Since the slab returned by get_partial() interfaces is not frozen anymore and no freelist is returned in the partial_context, so we need to use the introduced freeze_slab() to freeze it and get its freelist.
Similarly, the slabs on the CPU partial list are not frozen anymore, we need to freeze_slab() on it before use.
We can now delete acquire_slab() as it became unused.
Signed-off-by: Chengming Zhou zhouchengming@bytedance.com Reviewed-by: Vlastimil Babka vbabka@suse.cz Tested-by: Hyeonggon Yoo 42.hyeyoo@gmail.com Reviewed-by: Hyeonggon Yoo 42.hyeyoo@gmail.com Signed-off-by: Vlastimil Babka vbabka@suse.cz Signed-off-by: ZhangPeng zhangpeng362@huawei.com --- mm/slub.c | 115 ++++++++++++------------------------------------------ 1 file changed, 24 insertions(+), 91 deletions(-)
diff --git a/mm/slub.c b/mm/slub.c index c1dc6d4cf5a9..b00e20b26bb7 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -2166,7 +2166,7 @@ static inline void remove_partial(struct kmem_cache_node *n, }
/* - * Called only for kmem_cache_debug() caches instead of acquire_slab(), with a + * Called only for kmem_cache_debug() caches instead of remove_partial(), with a * slab from the n->partial list. Remove only a single object from the slab, do * the alloc_debug_processing() checks and leave the slab on the list, or move * it to full list if it was the last free object. @@ -2234,51 +2234,6 @@ static void *alloc_single_from_new_slab(struct kmem_cache *s, return object; }
-/* - * Remove slab from the partial list, freeze it and - * return the pointer to the freelist. - * - * Returns a list of objects or NULL if it fails. - */ -static inline void *acquire_slab(struct kmem_cache *s, - struct kmem_cache_node *n, struct slab *slab, - int mode) -{ - void *freelist; - unsigned long counters; - struct slab new; - - lockdep_assert_held(&n->list_lock); - - /* - * Zap the freelist and set the frozen bit. - * The old freelist is the list of objects for the - * per cpu allocation list. - */ - freelist = slab->freelist; - counters = slab->counters; - new.counters = counters; - if (mode) { - new.inuse = slab->objects; - new.freelist = NULL; - } else { - new.freelist = freelist; - } - - VM_BUG_ON(new.frozen); - new.frozen = 1; - - if (!__slab_update_freelist(s, slab, - freelist, counters, - new.freelist, new.counters, - "acquire_slab")) - return NULL; - - remove_partial(n, slab); - WARN_ON(!freelist); - return freelist; -} - #ifdef CONFIG_SLUB_CPU_PARTIAL static void put_cpu_partial(struct kmem_cache *s, struct slab *slab, int drain); #else @@ -2295,7 +2250,6 @@ static struct slab *get_partial_node(struct kmem_cache *s, struct partial_context *pc) { struct slab *slab, *slab2, *partial = NULL; - void *object = NULL; unsigned long flags; unsigned int partial_slabs = 0;
@@ -2314,7 +2268,7 @@ static struct slab *get_partial_node(struct kmem_cache *s, continue;
if (IS_ENABLED(CONFIG_SLUB_TINY) || kmem_cache_debug(s)) { - object = alloc_single_from_partial(s, n, slab, + void *object = alloc_single_from_partial(s, n, slab, pc->orig_size); if (object) { partial = slab; @@ -2324,13 +2278,10 @@ static struct slab *get_partial_node(struct kmem_cache *s, continue; }
- object = acquire_slab(s, n, slab, object == NULL); - if (!object) - break; + remove_partial(n, slab);
if (!partial) { partial = slab; - pc->object = object; stat(s, ALLOC_FROM_PARTIAL); } else { put_cpu_partial(s, slab, 0); @@ -2629,9 +2580,6 @@ static void __unfreeze_partials(struct kmem_cache *s, struct slab *partial_slab) unsigned long flags = 0;
while (partial_slab) { - struct slab new; - struct slab old; - slab = partial_slab; partial_slab = slab->next;
@@ -2644,23 +2592,7 @@ static void __unfreeze_partials(struct kmem_cache *s, struct slab *partial_slab) spin_lock_irqsave(&n->list_lock, flags); }
- do { - - old.freelist = slab->freelist; - old.counters = slab->counters; - VM_BUG_ON(!old.frozen); - - new.counters = old.counters; - new.freelist = old.freelist; - - new.frozen = 0; - - } while (!__slab_update_freelist(s, slab, - old.freelist, old.counters, - new.freelist, new.counters, - "unfreezing slab")); - - if (unlikely(!new.inuse && n->nr_partial >= s->min_partial)) { + if (unlikely(!slab->inuse && n->nr_partial >= s->min_partial)) { slab->next = slab_to_discard; slab_to_discard = slab; } else { @@ -3167,7 +3099,6 @@ static void *___slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node, node = NUMA_NO_NODE; goto new_slab; } -redo:
if (unlikely(!node_match(slab, node))) { /* @@ -3243,7 +3174,8 @@ static void *___slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node,
new_slab:
- if (slub_percpu_partial(c)) { +#ifdef CONFIG_SLUB_CPU_PARTIAL + while (slub_percpu_partial(c)) { local_lock_irqsave(&s->cpu_slab->lock, flags); if (unlikely(c->slab)) { local_unlock_irqrestore(&s->cpu_slab->lock, flags); @@ -3255,12 +3187,22 @@ static void *___slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node, goto new_objects; }
- slab = c->slab = slub_percpu_partial(c); + slab = slub_percpu_partial(c); slub_set_percpu_partial(c, slab); local_unlock_irqrestore(&s->cpu_slab->lock, flags); stat(s, CPU_PARTIAL_ALLOC); - goto redo; + + if (unlikely(!node_match(slab, node) || + !pfmemalloc_match(slab, gfpflags))) { + slab->next = NULL; + __unfreeze_partials(s, slab); + continue; + } + + freelist = freeze_slab(s, slab); + goto retry_load_slab; } +#endif
new_objects:
@@ -3268,8 +3210,8 @@ static void *___slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node, pc.orig_size = orig_size; slab = get_partial(s, node, &pc); if (slab) { - freelist = pc.object; if (kmem_cache_debug(s)) { + freelist = pc.object; /* * For debug caches here we had to go through * alloc_single_from_partial() so just store the @@ -3281,6 +3223,7 @@ static void *___slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node, return freelist; }
+ freelist = freeze_slab(s, slab); goto retry_load_slab; }
@@ -3682,18 +3625,8 @@ static void __slab_free(struct kmem_cache *s, struct slab *slab, was_frozen = new.frozen; new.inuse -= cnt; if ((!new.inuse || !prior) && !was_frozen) { - - if (kmem_cache_has_cpu_partial(s) && !prior) { - - /* - * Slab was on no list before and will be - * partially empty - * We can defer the list move and instead - * freeze it. - */ - new.frozen = 1; - - } else { /* Needs to be taken off a list */ + /* Needs to be taken off a list */ + if (!kmem_cache_has_cpu_partial(s) || prior) {
n = get_node(s, slab_nid(slab)); /* @@ -3723,9 +3656,9 @@ static void __slab_free(struct kmem_cache *s, struct slab *slab, * activity can be necessary. */ stat(s, FREE_FROZEN); - } else if (new.frozen) { + } else if (kmem_cache_has_cpu_partial(s) && !prior) { /* - * If we just froze the slab then put it onto the + * If we started with a full slab then put it onto the * per cpu partial list. */ put_cpu_partial(s, slab, 1);