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use libdivide for substantially faster division

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This commit is contained in:
Daniel Micay 2018-08-27 06:57:44 -04:00
parent 63b0c39343
commit c7b24f63f1
2 changed files with 2066 additions and 9 deletions
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2056
libdivide.h Normal file
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19
malloc.c
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@ -12,6 +12,8 @@
#include <malloc.h> #include <malloc.h>
#include "libdivide.h"
#include "malloc.h" #include "malloc.h"
#include "random.h" #include "random.h"
#include "util.h" #include "util.h"
@ -186,6 +188,8 @@ static struct size_class {
struct slab_metadata *slab_info; struct slab_metadata *slab_info;
struct slab_metadata *partial_slabs; struct slab_metadata *partial_slabs;
struct slab_metadata *free_slabs; struct slab_metadata *free_slabs;
struct libdivide_u32_t size_divisor;
struct libdivide_u64_t slab_size_divisor;
struct random_state rng; struct random_state rng;
size_t metadata_allocated; size_t metadata_allocated;
size_t metadata_count; size_t metadata_count;
@ -285,14 +289,9 @@ static void *get_slab(struct size_class *c, size_t slab_size, struct slab_metada
return (char *)c->class_region_start + (index * slab_size); return (char *)c->class_region_start + (index * slab_size);
} }
static struct slab_metadata *get_metadata(struct size_class *c, size_t slab_size, void *p) { static struct slab_metadata *get_metadata(struct size_class *c, void *p) {
size_t offset = (char *)p - (char *)c->class_region_start; size_t offset = (char *)p - (char *)c->class_region_start;
size_t index; size_t index = libdivide_u64_do(offset, &c->slab_size_divisor);
if (slab_size == PAGE_SIZE) {
index = offset >> PAGE_SHIFT;
} else {
index = offset / slab_size;
}
// still caught without this check either as a read access violation or "double free" // still caught without this check either as a read access violation or "double free"
if (index >= c->metadata_allocated) { if (index >= c->metadata_allocated) {
fatal_error("invalid free within a slab yet to be used"); fatal_error("invalid free within a slab yet to be used");
@ -401,9 +400,9 @@ static void slab_free(void *p) {
pthread_mutex_lock(&c->mutex); pthread_mutex_lock(&c->mutex);
struct slab_metadata *metadata = get_metadata(c, slab_size, p); struct slab_metadata *metadata = get_metadata(c, p);
void *slab = get_slab(c, slab_size, metadata); void *slab = get_slab(c, slab_size, metadata);
size_t slot = ((char *)p - (char *)slab) / size; size_t slot = libdivide_u32_do((char *)p - (char *)slab, &c->size_divisor);
if (slot_pointer(size, slab, slot) != p) { if (slot_pointer(size, slab, slot) != p) {
fatal_error("invalid unaligned free"); fatal_error("invalid unaligned free");
@ -637,6 +636,8 @@ COLD static void init_slow_path(void) {
if (size == 0) { if (size == 0) {
size = 16; size = 16;
} }
c->size_divisor = libdivide_u32_gen(size);
c->slab_size_divisor = libdivide_u64_gen(get_slab_size(size_class_slots[i], size));
size_t slots = size_class_slots[i]; size_t slots = size_class_slots[i];
size_t metadata_max = get_metadata_max(get_slab_size(slots, size)); size_t metadata_max = get_metadata_max(get_slab_size(slots, size));
c->slab_info = allocate_pages(metadata_max * sizeof(struct slab_metadata), PAGE_SIZE, false); c->slab_info = allocate_pages(metadata_max * sizeof(struct slab_metadata), PAGE_SIZE, false);