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calculate slab size class instead of array loop

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Daniel Micay 2022-01-16 14:05:59 -05:00
parent d8cb2d9f7a
commit 81cf2f27a0
2 changed files with 17 additions and 13 deletions
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22
h_malloc.c
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@ -196,13 +196,16 @@ static inline struct size_info get_size_info(size_t size) {
if (size <= 128) { if (size <= 128) {
return (struct size_info){align(size, 16), ((size - 1) >> 4) + 1}; return (struct size_info){align(size, 16), ((size - 1) >> 4) + 1};
} }
for (unsigned class = 9; class < N_SIZE_CLASSES; class++) {
size_t real_size = size_classes[class]; const size_t initial_spacing_multiplier = 5;
if (size <= real_size) { const size_t special_small_sizes = 5; // 0, 16, 32, 48, 64
return (struct size_info){real_size, class};
} size_t spacing_class_shift = log2u64(size - 1) - 2;
} size_t spacing_class = 1ULL << spacing_class_shift;
fatal_error("invalid size for slabs"); size_t real_size = align(size, spacing_class);
size_t spacing_class_index = (real_size >> spacing_class_shift) - initial_spacing_multiplier;
size_t index = (spacing_class_shift - 4) * 4 + special_small_sizes + spacing_class_index;
return (struct size_info){real_size, index};
} }
// alignment must be a power of 2 <= PAGE_SIZE since slabs are only page aligned // alignment must be a power of 2 <= PAGE_SIZE since slabs are only page aligned
@ -1199,10 +1202,7 @@ static size_t get_large_size_class(size_t size) {
// 512 KiB [2560 KiB, 3 MiB, 3584 KiB, 4 MiB] // 512 KiB [2560 KiB, 3 MiB, 3584 KiB, 4 MiB]
// 1 MiB [5 MiB, 6 MiB, 7 MiB, 8 MiB] // 1 MiB [5 MiB, 6 MiB, 7 MiB, 8 MiB]
// etc. // etc.
size = max(size, (size_t)PAGE_SIZE); return get_size_info(max(size, (size_t)PAGE_SIZE)).size;
size_t spacing_shift = U64_WIDTH - clz64(size - 1) - 3;
size_t spacing_class = 1ULL << spacing_shift;
return align(size, spacing_class);
} }
return page_align(size); return page_align(size);
} }

8
util.h
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@ -35,6 +35,8 @@ typedef uint32_t u32;
typedef uint64_t u64; typedef uint64_t u64;
typedef unsigned __int128 u128; typedef unsigned __int128 u128;
#define U64_WIDTH 64
static inline int clz64(u64 x) { static inline int clz64(u64 x) {
return __builtin_clzll(x); return __builtin_clzll(x);
} }
@ -43,6 +45,10 @@ static inline int ffz64(u64 x) {
return __builtin_ffsll(~x); return __builtin_ffsll(~x);
} }
static inline u64 log2u64(u64 x) {
return U64_WIDTH - clz64(x) - 1;
}
static inline size_t align(size_t size, size_t align) { static inline size_t align(size_t size, size_t align) {
size_t mask = align - 1; size_t mask = align - 1;
return (size + mask) & ~mask; return (size + mask) & ~mask;
@ -50,8 +56,6 @@ static inline size_t align(size_t size, size_t align) {
COLD noreturn void fatal_error(const char *s); COLD noreturn void fatal_error(const char *s);
#define U64_WIDTH 64
#if CONFIG_SEAL_METADATA #if CONFIG_SEAL_METADATA
#ifdef __GLIBC__ #ifdef __GLIBC__