The patch titled
Subject: slab: make kmalloc_index() return "unsigned int"
has been added to the -mm tree. Its filename is
slab-make-kmalloc_index-return-unsigned-int.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/slab-make-kmalloc_index-return-unsigned-int.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/slab-make-kmalloc_index-return-unsigned-int.patch
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From: Alexey Dobriyan <adobriyan@xxxxxxxxx>
Subject: slab: make kmalloc_index() return "unsigned int"
kmalloc_index() return index into an array of kmalloc kmem caches,
therefore should be unsigned.
Space savings with SLUB on trimmed down .config:
add/remove: 0/1 grow/shrink: 6/56 up/down: 85/-557 (-472)
Function old new delta
calculate_sizes 924 983 +59
on_freelist 589 604 +15
init_cache_random_seq 122 127 +5
ext4_mb_init 1206 1210 +4
slab_pad_check.part 270 271 +1
cpu_partial_store 112 113 +1
usersize_show 28 27 -1
...
new_slab 1871 1837 -34
slab_order 204 - -204
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 memset/memcpy
takes size_t so should everything passed 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.
Link: http://lkml.kernel.org/r/20180305200730.15812-2-adobriyan@xxxxxxxxx
Signed-off-by: Alexey Dobriyan <adobriyan@xxxxxxxxx>
Cc: Christoph Lameter <cl@xxxxxxxxx>
Cc: Pekka Enberg <penberg@xxxxxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/slab.h | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff -puN include/linux/slab.h~slab-make-kmalloc_index-return-unsigned-int include/linux/slab.h
--- a/include/linux/slab.h~slab-make-kmalloc_index-return-unsigned-int
+++ a/include/linux/slab.h
@@ -308,7 +308,7 @@ extern struct kmem_cache *kmalloc_dma_ca
* 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;
@@ -504,7 +504,7 @@ static __always_inline void *kmalloc(siz
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;
@@ -542,7 +542,7 @@ static __always_inline void *kmalloc_nod
#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;
_
Patches currently in -mm which might be from adobriyan@xxxxxxxxx are
slab-mark-kmalloc-machinery-as-__ro_after_init.patch
slab-fixup-calculate_alignment-argument-type.patch
slab-make-kmalloc_index-return-unsigned-int.patch
slab-make-kmalloc_size-return-unsigned-int.patch
slab-make-create_kmalloc_cache-work-with-32-bit-sizes.patch
slab-make-create_boot_cache-work-with-32-bit-sizes.patch
slab-make-kmem_cache_create-work-with-32-bit-sizes.patch
slab-make-size_index-array-u8.patch
slab-make-size_index_elem-unsigned-int.patch
slub-make-remote_node_defrag_ratio-unsigned-int.patch
slub-make-max_attr_size-unsigned-int.patch
slub-make-red_left_pad-unsigned-int.patch
slub-make-reserved-unsigned-int.patch
slub-make-align-unsigned-int.patch
slub-make-inuse-unsigned-int.patch
slub-make-cpu_partial-unsigned-int.patch
slub-make-offset-unsigned-int.patch
slub-make-object_size-unsigned-int.patch
slub-make-size-unsigned-int.patch
slab-make-kmem_cache_flags-accept-32-bit-object-size.patch
kasan-make-kasan_cache_create-work-with-32-bit-slab-cache-sizes.patch
slab-make-usercopy-region-32-bit.patch
slub-make-slab_index-return-unsigned-int.patch
slub-make-struct-kmem_cache_order_objects-x-unsigned-int.patch
slub-make-size_from_object-return-unsigned-int.patch
slab-use-32-bit-arithmetic-in-freelist_randomize.patch
proc-do-less-stuff-under-pde_unload_lock.patch
proc-move-proc-sysvipc-creation-to-where-it-belongs.patch
proc-faster-open-close-of-files-without-release-hook.patch
proc-randomize-struct-pde_opener.patch
proc-move-struct-pde_opener-to-kmem-cache.patch
proc-account-struct-pde_opener.patch
proc-check-permissions-earlier-for-proc-wchan.patch
proc-use-set_puts-at-proc-wchan.patch
proc-test-proc-self-wchan.patch
proc-test-proc-self-syscall.patch
uts-create-struct-uts_namespace-from-kmem_cache.patch
seq_file-delete-small-value-optimization.patch
--
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