kmalloc() and kmalloc_node() is always inlined into generic code.
However, there is a mistake in implemention of the SLUB.
In kmalloc() and kmalloc_node() of the SLUB,
we try to compare kmalloc_caches[index] with NULL.
As it cannot be known at compile time,
this comparison is inserted into generic code invoking kmalloc*.
This may decrease system performance, so we should fix it.
Below is the result of "size vmlinux"
text size is decreased roughly 20KB
Before:
text data bss dec hex filename
10044177 1443168 5722112 17209457 1069871 vmlinux
After:
text data bss dec hex filename
10022627 1443136 5722112 17187875 1064423 vmlinux
Cc: Christoph Lameter <cl@xxxxxxxxx>
Signed-off-by: Joonsoo Kim <js1304@xxxxxxxxx>
---
With Christoph's patchset(common kmalloc caches:
'[15/15] Common Kmalloc cache determination') which is not merged into mainline yet,
this issue will be fixed.
As it takes some time, I send this patch for v3.7
This patch is based on v3.7-rc1
diff --git a/include/linux/slub_def.h b/include/linux/slub_def.h
index df448ad..4c75f2b 100644
--- a/include/linux/slub_def.h
+++ b/include/linux/slub_def.h
@@ -271,9 +271,10 @@ static __always_inline void *kmalloc(size_t size, gfp_t flags)
return kmalloc_large(size, flags);
if (!(flags & SLUB_DMA)) {
- struct kmem_cache *s = kmalloc_slab(size);
+ int index = kmalloc_index(size);
+ struct kmem_cache *s = kmalloc_caches[index];
- if (!s)
+ if (!index)
return ZERO_SIZE_PTR;
return kmem_cache_alloc_trace(s, flags, size);
@@ -304,9 +305,10 @@ static __always_inline void *kmalloc_node(size_t size, gfp_t flags, int node)
{
if (__builtin_constant_p(size) &&
size <= SLUB_MAX_SIZE && !(flags & SLUB_DMA)) {
- struct kmem_cache *s = kmalloc_slab(size);
+ int index = kmalloc_index(size);
+ struct kmem_cache *s = kmalloc_caches[index];
- if (!s)
+ if (!index)
return ZERO_SIZE_PTR;
return kmem_cache_alloc_node_trace(s, flags, node, size);
--
1.7.9.5
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