[PATCH v2] slub: use free_page instead of put_page for freeing kmalloc allocation

[PATCH v2] slub: use free_page instead of put_page for freeing kmalloc allocation

[Glauber Costa]

When freeing objects, the slub allocator will most of the time free
empty pages by calling __free_pages(). But high-order kmalloc will be
diposed by means of put_page() instead. It makes no sense to call
put_page() in kernel pages that are provided by the object allocators,
so we shouldn't be doing this ourselves. Aside from the consistency
change, we don't change the flow too much. put_page()'s would call its
dtor function, which is __free_pages. We also already do all of the
Compound page tests ourselves, and the Mlock test we lose don't really
matter.

[v2: modified Changelog ]

Signed-off-by: Glauber Costa <glommer@parallels.com>
Acked-by: Christoph Lameter <cl@linux.com>
CC: David Rientjes <rientjes@google.com>
CC: Pekka Enberg <penberg@kernel.org>
---
 mm/slub.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/slub.c b/mm/slub.c
index e517d43..9ca4e20 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -3453,7 +3453,7 @@ void kfree(const void *x)
 	if (unlikely(!PageSlab(page))) {
 		BUG_ON(!PageCompound(page));
 		kmemleak_free(x);
-		put_page(page);
+		__free_pages(page, compound_order(page));
 		return;
 	}
 	slab_free(page->slab, page, object, _RET_IP_);
-- 
1.7.11.2

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>

Re: [PATCH v2] slub: use free_page instead of put_page for freeing kmalloc allocation

[Pekka Enberg]

On Fri, Aug 3, 2012 at 9:51 PM, Glauber Costa <glommer@parallels.com> wrote:
> When freeing objects, the slub allocator will most of the time free
> empty pages by calling __free_pages(). But high-order kmalloc will be
> diposed by means of put_page() instead. It makes no sense to call
> put_page() in kernel pages that are provided by the object allocators,
> so we shouldn't be doing this ourselves. Aside from the consistency
> change, we don't change the flow too much. put_page()'s would call its
> dtor function, which is __free_pages. We also already do all of the
> Compound page tests ourselves, and the Mlock test we lose don't really
> matter.
>
> [v2: modified Changelog ]
>
> Signed-off-by: Glauber Costa <glommer@parallels.com>
> Acked-by: Christoph Lameter <cl@linux.com>
> CC: David Rientjes <rientjes@google.com>
> CC: Pekka Enberg <penberg@kernel.org>

Applied, thanks!

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>