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add a special memory protected 0 byte size class

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This commit is contained in:
Daniel Micay 2018-08-24 03:22:52 -04:00
parent 27ac1e21bc
commit 0d51459dc9
1 changed files with 10 additions and 2 deletions
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12
malloc.c
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@ -140,6 +140,7 @@ struct slab_metadata {
static const size_t max_slab_size_class = 16384;
static const uint16_t size_classes[] = {
/* 0 */ 0,
/* 16 */ 16, 32, 48, 64, 80, 96, 112, 128,
/* 32 */ 160, 192, 224, 256,
/* 64 */ 320, 384, 448, 512,
@ -151,6 +152,7 @@ static const uint16_t size_classes[] = {
};
static const uint16_t size_class_slots[] = {
/* 0 */ 256,
/* 16 */ 256, 128, 85, 64, 51, 42, 36, 64,
/* 32 */ 51, 64, 54, 64,
/* 64 */ 64, 64, 64, 64,
@ -169,7 +171,10 @@ struct size_info {
};
static struct size_info get_size_info(size_t size) {
for (size_t i = 0; i < N_SIZE_CLASSES; i++) {
if (size == 0) {
return (struct size_info){16, 0};
}
for (size_t i = 1; i < N_SIZE_CLASSES; i++) {
size_t real_size = size_classes[i];
if (size <= real_size) {
return (struct size_info){real_size, i};
@ -318,7 +323,7 @@ static void *slab_allocate(size_t requested_size) {
}
void *slab = get_slab(c, slab_size, metadata);
if (mprotect(slab, slab_size, PROT_READ|PROT_WRITE)) {
if (requested_size != 0 && mprotect(slab, slab_size, PROT_READ|PROT_WRITE)) {
metadata->next = c->free_slabs;
if (c->free_slabs) {
c->free_slabs->prev = metadata;
@ -596,6 +601,9 @@ COLD static void init_slow_path(void) {
c->class_region_start = (char *)ro.slab_region_start + class_region_size * i + gap;
size_t size = size_classes[i];
if (size == 0) {
size = 16;
}
size_t slots = size_class_slots[i];
size_t metadata_max = get_metadata_max(get_slab_size(slots, size));
c->slab_info = allocate_pages(metadata_max * sizeof(struct slab_metadata), false);