mirrors
/
linux-stable
mirror of https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
1
0
Fork 0
Code Issues Releases Wiki Activity

slub: Delay freezing of partial slabs 

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>
This commit is contained in:
Chengming Zhou 2023-11-02 03:23:27 +00:00 committed by Vlastimil Babka
parent 213094b5d1
commit 8cd3fa428b
1 changed files with 24 additions and 91 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

115
mm/slub.c
View File

@ -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 @@ reread_slab:
node = NUMA_NO_NODE;
goto new_slab;
}
redo:
if (unlikely(!node_match(slab, node))) {
/*
@ -3243,7 +3174,8 @@ deactivate_slab:
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 @@ new_slab:
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 @@ new_objects:
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 @@ new_objects:
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);