Hello, Pekka.
Could you pick up 1/3, 3/3?
These are already acked by Christoph.
2/3 is same effect as Glauber's "slub: correctly bootstrap boot caches",
so should skip it.
Thanks.
On Mon, Jan 21, 2013 at 05:01:25PM +0900, Joonsoo Kim wrote:
> There is a subtle bug when calculating a number of acquired objects.
>
> Currently, we calculate "available = page->objects - page->inuse",
> after acquire_slab() is called in get_partial_node().
>
> In acquire_slab() with mode = 1, we always set new.inuse = page->objects.
> So,
>
> acquire_slab(s, n, page, object == NULL);
>
> if (!object) {
> c->page = page;
> stat(s, ALLOC_FROM_PARTIAL);
> object = t;
> available = page->objects - page->inuse;
>
> !!! availabe is always 0 !!!
> ...
>
> Therfore, "available > s->cpu_partial / 2" is always false and
> we always go to second iteration.
> This patch correct this problem.
>
> After that, we don't need return value of put_cpu_partial().
> So remove it.
>
> v2: calculate nr of objects using new.objects and new.inuse.
> It is more accurate way than before.
>
> Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
>
> diff --git a/mm/slub.c b/mm/slub.c
> index ba2ca53..7204c74 100644
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -1493,7 +1493,7 @@ static inline void remove_partial(struct kmem_cache_node *n,
> */
> static inline void *acquire_slab(struct kmem_cache *s,
> struct kmem_cache_node *n, struct page *page,
> - int mode)
> + int mode, int *objects)
> {
> void *freelist;
> unsigned long counters;
> @@ -1507,6 +1507,7 @@ static inline void *acquire_slab(struct kmem_cache *s,
> freelist = page->freelist;
> counters = page->counters;
> new.counters = counters;
> + *objects = new.objects - new.inuse;
> if (mode) {
> new.inuse = page->objects;
> new.freelist = NULL;
> @@ -1528,7 +1529,7 @@ static inline void *acquire_slab(struct kmem_cache *s,
> return freelist;
> }
>
> -static int put_cpu_partial(struct kmem_cache *s, struct page *page, int drain);
> +static void put_cpu_partial(struct kmem_cache *s, struct page *page, int drain);
> static inline bool pfmemalloc_match(struct page *page, gfp_t gfpflags);
>
> /*
> @@ -1539,6 +1540,8 @@ static void *get_partial_node(struct kmem_cache *s, struct kmem_cache_node *n,
> {
> struct page *page, *page2;
> void *object = NULL;
> + int available = 0;
> + int objects;
>
> /*
> * Racy check. If we mistakenly see no partial slabs then we
> @@ -1552,22 +1555,21 @@ static void *get_partial_node(struct kmem_cache *s, struct kmem_cache_node *n,
> spin_lock(&n->list_lock);
> list_for_each_entry_safe(page, page2, &n->partial, lru) {
> void *t;
> - int available;
>
> if (!pfmemalloc_match(page, flags))
> continue;
>
> - t = acquire_slab(s, n, page, object == NULL);
> + t = acquire_slab(s, n, page, object == NULL, &objects);
> if (!t)
> break;
>
> + available += objects;
> if (!object) {
> c->page = page;
> stat(s, ALLOC_FROM_PARTIAL);
> object = t;
> - available = page->objects - page->inuse;
> } else {
> - available = put_cpu_partial(s, page, 0);
> + put_cpu_partial(s, page, 0);
> stat(s, CPU_PARTIAL_NODE);
> }
> if (kmem_cache_debug(s) || available > s->cpu_partial / 2)
> @@ -1946,7 +1948,7 @@ static void unfreeze_partials(struct kmem_cache *s,
> * If we did not find a slot then simply move all the partials to the
> * per node partial list.
> */
> -static int put_cpu_partial(struct kmem_cache *s, struct page *page, int drain)
> +static void put_cpu_partial(struct kmem_cache *s, struct page *page, int drain)
> {
> struct page *oldpage;
> int pages;
> @@ -1984,7 +1986,6 @@ static int put_cpu_partial(struct kmem_cache *s, struct page *page, int drain)
> page->next = oldpage;
>
> } while (this_cpu_cmpxchg(s->cpu_slab->partial, oldpage, page) != oldpage);
> - return pobjects;
> }
>
> static inline void flush_slab(struct kmem_cache *s, struct kmem_cache_cpu *c)
> --
> 1.7.9.5
>
> --
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