The commit d6e0b7fa1186 ("slub: make dead caches discard free slabs
immediately") introduced those logic to speed up the destruction of
per-memcg kmem caches, because kmem caches created for a memory
cgroup are only destroyed after the last page charged to the cgroup
is freed at that time. But since commit 9855609bde03 ("mm: memcg/slab:
use a single set of kmem_caches for all accounted allocations), we
do not have per-memcg kmem caches anymore. Are those code pointless?
No, the kmem_cache->cpu_partial can be set to zero by 'echo 0 > /sys/
kernel/slab/*/cpu_partial'. In this case, the slab page will be put
into cpu partial list and then moved to node list (because
slub_cpu_partial() returns zero). However, we can skip putting the
slab page to cpu partial list and just move it to node list directly.
We can adjust the condition of kmem_cache_has_cpu_partial() to
slub_cpu_partial() in __slab_free() and remove those code from
put_cpu_partial() for simplification.
Signed-off-by: Muchun Song <songmuchun@xxxxxxxxxxxxx>
---
mm/slub.c | 23 +++--------------------
1 file changed, 3 insertions(+), 20 deletions(-)
diff --git a/mm/slub.c b/mm/slub.c
index b6c5205252eb..69c8ada322a0 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -2438,7 +2438,6 @@ static void put_cpu_partial(struct kmem_cache *s, struct page *page, int drain)
int pages;
int pobjects;
- preempt_disable();
do {
pages = 0;
pobjects = 0;
@@ -2470,16 +2469,7 @@ static void put_cpu_partial(struct kmem_cache *s, struct page *page, int drain)
page->pobjects = pobjects;
page->next = oldpage;
- } while (this_cpu_cmpxchg(s->cpu_slab->partial, oldpage, page)
- != oldpage);
- if (unlikely(!slub_cpu_partial(s))) {
- unsigned long flags;
-
- local_irq_save(flags);
- unfreeze_partials(s, this_cpu_ptr(s->cpu_slab));
- local_irq_restore(flags);
- }
- preempt_enable();
+ } while (this_cpu_cmpxchg(s->cpu_slab->partial, oldpage, page) != oldpage);
#endif /* CONFIG_SLUB_CPU_PARTIAL */
}
@@ -3059,9 +3049,7 @@ static void __slab_free(struct kmem_cache *s, struct page *page,
was_frozen = new.frozen;
new.inuse -= cnt;
if ((!new.inuse || !prior) && !was_frozen) {
-
- if (kmem_cache_has_cpu_partial(s) && !prior) {
-
+ if (slub_cpu_partial(s) && !prior) {
/*
* Slab was on no list before and will be
* partially empty
@@ -3069,9 +3057,7 @@ static void __slab_free(struct kmem_cache *s, struct page *page,
* freeze it.
*/
new.frozen = 1;
-
} else { /* Needs to be taken off a list */
-
n = get_node(s, page_to_nid(page));
/*
* Speculatively acquire the list_lock.
@@ -3082,17 +3068,14 @@ static void __slab_free(struct kmem_cache *s, struct page *page,
* other processors updating the list of slabs.
*/
spin_lock_irqsave(&n->list_lock, flags);
-
}
}
-
} while (!cmpxchg_double_slab(s, page,
prior, counters,
head, new.counters,
"__slab_free"));
if (likely(!n)) {
-
if (likely(was_frozen)) {
/*
* The list lock was not taken therefore no list
@@ -3118,7 +3101,7 @@ static void __slab_free(struct kmem_cache *s, struct page *page,
* Objects left in the slab. If it was not on the partial list before
* then add it.
*/
- if (!kmem_cache_has_cpu_partial(s) && unlikely(!prior)) {
+ if (unlikely(!prior)) {
remove_full(s, n, page);
add_partial(n, page, DEACTIVATE_TO_TAIL);
stat(s, FREE_ADD_PARTIAL);
--
2.11.0
