Hello, Christoph.
On Mon, Apr 01, 2013 at 03:33:23PM +0000, Christoph Lameter wrote:
> Subject: slub: Fix object counts in acquire_slab V2
>
> It seems that we were overallocating objects from the slab queues
> since get_partial_node() assumed that page->inuse was undisturbed by
> acquire_slab(). Save the # of objects in page->lru.next in acquire_slab()
> and pass it to get_partial_node() that way.
>
> I have a vague memory that Joonsoo also ran into this issue awhile back.
Yes. I sent a patch for this two month ago. :)
>
> Signed-off-by: Christoph Lameter <cl@xxxxxxxxx>
>
> Index: linux/mm/slub.c
> ===================================================================
> --- linux.orig/mm/slub.c 2013-03-28 12:14:26.958358688 -0500
> +++ linux/mm/slub.c 2013-04-01 10:23:24.677584499 -0500
> @@ -1498,6 +1498,7 @@ static inline void *acquire_slab(struct
> void *freelist;
> unsigned long counters;
> struct page new;
> + unsigned long objects;
>
> /*
> * Zap the freelist and set the frozen bit.
> @@ -1507,6 +1508,7 @@ static inline void *acquire_slab(struct
> freelist = page->freelist;
> counters = page->counters;
> new.counters = counters;
> + objects = page->inuse;
> if (mode) {
> new.inuse = page->objects;
> new.freelist = NULL;
> @@ -1524,6 +1526,7 @@ static inline void *acquire_slab(struct
> return NULL;
>
> remove_partial(n, page);
> + page->lru.next = (void *)objects;
> WARN_ON(!freelist);
> return freelist;
> }
Good. I like your method which use lru.next in order to hand over
number of objects.
> @@ -1565,7 +1568,7 @@ static void *get_partial_node(struct kme
> c->page = page;
> stat(s, ALLOC_FROM_PARTIAL);
> object = t;
> - available = page->objects - page->inuse;
> + available = page->objects - (unsigned long)page->lru.next;
> } else {
> available = put_cpu_partial(s, page, 0);
> stat(s, CPU_PARTIAL_NODE);
We need one more fix for correctness.
When available is assigned by put_cpu_partial, it doesn't count cpu slab's objects.
Please reference my old patch.
https://lkml.org/lkml/2013/1/21/64
Thanks.
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