From: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
On x86, SLUB creates and handles <=8192-byte allocations internally.
It passes larger ones up to the allocator. Saying "up to order 2" is,
at best, ambiguous. Is that order-1? Or (order-2 bytes)? Make
it more clear.
SLOB commits a similar sin. It *handles* page-size requests, but the
comment says that it passes up "all page size and larger requests".
SLOB also swaps around the order of the very-similarly-named
KMALLOC_SHIFT_HIGH and KMALLOC_SHIFT_MAX #defines. Make it
consistent with the order of the other two allocators.
Signed-off-by: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Cc: Christoph Lameter <cl@xxxxxxxxxxxxxxxxxxxx>
Cc: Pekka Enberg <penberg@xxxxxxxxxx>
Cc: Matt Mackall <mpm@xxxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
b/include/linux/slab.h | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff -puN include/linux/slab.h~mm-slub-off-by-one-comment-on-kmalloc-max include/linux/slab.h
--- a/include/linux/slab.h~mm-slub-off-by-one-comment-on-kmalloc-max 2014-01-28 13:27:50.883108273 -0800
+++ b/include/linux/slab.h 2014-01-28 13:27:50.886108408 -0800
@@ -205,8 +205,8 @@ struct kmem_cache {
#ifdef CONFIG_SLUB
/*
- * SLUB allocates up to order 2 pages directly and otherwise
- * passes the request to the page allocator.
+ * SLUB directly allocates requests fitting in to an order-1 page
+ * (PAGE_SIZE*2). Larger requests are passed to the page allocator.
*/
#define KMALLOC_SHIFT_HIGH (PAGE_SHIFT + 1)
#define KMALLOC_SHIFT_MAX (MAX_ORDER + PAGE_SHIFT)
@@ -217,12 +217,12 @@ struct kmem_cache {
#ifdef CONFIG_SLOB
/*
- * SLOB passes all page size and larger requests to the page allocator.
+ * SLOB passes all requests larger than one page to the page allocator.
* No kmalloc array is necessary since objects of different sizes can
* be allocated from the same page.
*/
-#define KMALLOC_SHIFT_MAX 30
#define KMALLOC_SHIFT_HIGH PAGE_SHIFT
+#define KMALLOC_SHIFT_MAX 30
#ifndef KMALLOC_SHIFT_LOW
#define KMALLOC_SHIFT_LOW 3
#endif
_
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@xxxxxxxxx. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>