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fix overly naive slab allocation alignment support

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This commit is contained in:
Daniel Micay 2018-09-10 17:42:58 -04:00
parent 9a1acce5eb
commit 61684925e8
1 changed files with 14 additions and 2 deletions
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16
malloc.c
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@ -47,6 +47,7 @@ struct slab_metadata {
uint64_t canary_value; uint64_t canary_value;
}; };
static const size_t min_align = 16;
static const size_t max_slab_size_class = 16384; static const size_t max_slab_size_class = 16384;
static const uint16_t size_classes[] = { static const uint16_t size_classes[] = {
@ -93,6 +94,17 @@ static inline struct size_info get_size_info(size_t size) {
fatal_error("invalid size for slabs"); fatal_error("invalid size for slabs");
} }
// alignment must be a power of 2 <= PAGE_SIZE since slabs are only page aligned
static inline struct size_info get_size_info_align(size_t size, size_t alignment) {
for (unsigned class = 1; class < N_SIZE_CLASSES; class++) {
size_t real_size = size_classes[class];
if (size <= real_size && !(real_size & (alignment - 1))) {
return (struct size_info){real_size, class};
}
}
fatal_error("invalid size for slabs");
}
static size_t get_slab_size(size_t slots, size_t size) { static size_t get_slab_size(size_t slots, size_t size) {
return PAGE_CEILING(slots * size); return PAGE_CEILING(slots * size);
} }
@ -892,8 +904,8 @@ static int alloc_aligned(void **memptr, size_t alignment, size_t size, size_t mi
} }
if (alignment <= PAGE_SIZE) { if (alignment <= PAGE_SIZE) {
if (size < alignment) { if (size <= max_slab_size_class && alignment > min_align) {
size = alignment; size = get_size_info_align(size, alignment).size;
} }
void *p = allocate(size); void *p = allocate(size);