Commit 433a91ff authored Jan 28, 2014 by Dave Hansen Committed by Pekka Enberg Jan 31, 2014

mm: sl[uo]b: fix misleading comments



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.

Cc: Matt Mackall <mpm@selenic.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Christoph Lameter <cl@linux-foundation.org>
Acked-by: David Rientjes <rientjes@google.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Signed-off-by: Pekka Enberg <penberg@kernel.org>

parent 26e4f205

include/linux/slab.h

+4 −4

Original line number	Diff line number	Diff line
		@@ -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

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