kmalloc_index() return index into an array of kmalloc kmem caches,
therefore should unsigned.
Space savings:
add/remove: 0/0 grow/shrink: 0/2 up/down: 0/-6 (-6)
Function old new delta
rtsx_scsi_handler 9116 9114 -2
vnic_rq_alloc 424 420 -4
This patch start a series of converting SLUB (mostly) to "unsigned int".
1) Most integers in the code are in fact unsigned entities: array indexes,
lengths, buffer sizes, allocation orders. It is therefore better to use
unsigned variables
2) Some integers in the code are either "size_t" or "unsigned long" for no
reason.
size_t usually comes from people trying to "maintain" type correctness
and figuring out that "sizeof" operator returns size_t or that
memset/memcpy takes size_t so should everything you pass to it.
However the number of 4GB+ objects in the kernel is very small.
Most, if not all, dynamically allocated objects with kmalloc() or
kmem_cache_create() aren't actually big. Maintaining wide types
doesn't do anything.
64-bit ops are bigger than 32-bit on our beloved x86_64,
so try to not use 64-bit where it isn't necessary
(read: everywhere where integers are integers not pointers)
3) in case of SLAB allocators, there are additional limitations
*) page->inuse, page->objects are only 16-/15-bit,
*) cache size was always 32-bit
*) slab orders are small, order 20 is needed to go 64-bit on x86_64
(PAGE_SIZE << order)
Basically everything is 32-bit except kmalloc(1ULL<<32) which gets shortcut
through page allocator.
Signed-off-by: Alexey Dobriyan <adobriyan@xxxxxxxxx>
---
include/linux/slab.h | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/include/linux/slab.h b/include/linux/slab.h
index 50697a1d6621..e765800d7c9b 100644
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -295,7 +295,7 @@ extern struct kmem_cache *kmalloc_dma_caches[KMALLOC_SHIFT_HIGH + 1];
* 2 = 129 .. 192 bytes
* n = 2^(n-1)+1 .. 2^n
*/
-static __always_inline int kmalloc_index(size_t size)
+static __always_inline unsigned int kmalloc_index(size_t size)
{
if (!size)
return 0;
@@ -491,7 +491,7 @@ static __always_inline void *kmalloc(size_t size, gfp_t flags)
return kmalloc_large(size, flags);
#ifndef CONFIG_SLOB
if (!(flags & GFP_DMA)) {
- int index = kmalloc_index(size);
+ unsigned int index = kmalloc_index(size);
if (!index)
return ZERO_SIZE_PTR;
@@ -529,7 +529,7 @@ static __always_inline void *kmalloc_node(size_t size, gfp_t flags, int node)
#ifndef CONFIG_SLOB
if (__builtin_constant_p(size) &&
size <= KMALLOC_MAX_CACHE_SIZE && !(flags & GFP_DMA)) {
- int i = kmalloc_index(size);
+ unsigned int i = kmalloc_index(size);
if (!i)
return ZERO_SIZE_PTR;
--
2.13.6
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