From 95203fe78007f9ab3aebb96606473ae18c00a5a8 Mon Sep 17 00:00:00 2001 From: Andrew Morton Date: Tue, 10 Jun 2003 10:09:28 -0700 Subject: [PATCH] optimize fixed-sized kmalloc calls From: Manfred Spraul and Brian Gerst The patch performs the kmalloc cache lookup for constant kmalloc calls at compile time. The idea is that the loop in kmalloc takes a significant amount of time, and for kmalloc(4096,GFP_KERNEL), that lookup can happen entirely at compile time. A problem has been seen with gcc-3.2.2-5 from RedHat. This code: if(__builtin_constant_t(size)) { if(size < 32) return kmem_cache_alloc(...); if(size < 64) return kmem_cache_alloc(...); if(size < 96) return kmem_cache_alloc(...); if(size < 128) return kmem_cache_alloc(...); ... } doesn't work, because gcc only optimizes the first two or three comparisons, and then suddenly generates code. But we did it that way anyway. Apparently it's fixed in later compilers. --- include/linux/slab.h | 33 ++++++++++++++++++++++++++++++++- 1 file changed, 32 insertions(+), 1 deletion(-) (limited to 'include') diff --git a/include/linux/slab.h b/include/linux/slab.h index 3e4e5491102c..138bcdf65275 100644 --- a/include/linux/slab.h +++ b/include/linux/slab.h @@ -62,7 +62,38 @@ extern void *kmem_cache_alloc(kmem_cache_t *, int); extern void kmem_cache_free(kmem_cache_t *, void *); extern unsigned int kmem_cache_size(kmem_cache_t *); -extern void *kmalloc(size_t, int); +/* Size description struct for general caches. */ +struct cache_sizes { + size_t cs_size; + kmem_cache_t *cs_cachep; + kmem_cache_t *cs_dmacachep; +}; +extern struct cache_sizes malloc_sizes[]; +extern void *__kmalloc(size_t, int); + +static inline void *kmalloc(size_t size, int flags) +{ + if (__builtin_constant_p(size)) { + int i = 0; +#define CACHE(x) \ + if (size <= x) \ + goto found; \ + else \ + i++; +#include "kmalloc_sizes.h" +#undef CACHE + { + extern void __you_cannot_kmalloc_that_much(void); + __you_cannot_kmalloc_that_much(); + } +found: + return kmem_cache_alloc((flags & GFP_DMA) ? + malloc_sizes[i].cs_dmacachep : + malloc_sizes[i].cs_cachep, flags); + } + return __kmalloc(size, flags); +} + extern void kfree(const void *); extern unsigned int ksize(const void *); -- cgit v1.2.3