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use FIFO queue for free slabs

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This commit is contained in:
Daniel Micay 2018-08-31 22:42:34 -04:00
parent dba330fde7
commit fad10ce943
1 changed files with 36 additions and 9 deletions
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45
malloc.c
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@ -166,16 +166,31 @@ static size_t get_slab_size(size_t slots, size_t size) {
return PAGE_CEILING(slots * size); return PAGE_CEILING(slots * size);
} }
// limit on the number of cached empty slabs before attempting purging instead
static const size_t max_empty_slabs_total = 64 * 1024; static const size_t max_empty_slabs_total = 64 * 1024;
static struct size_class { static struct size_class {
pthread_mutex_t mutex; pthread_mutex_t mutex;
void *class_region_start; void *class_region_start;
struct slab_metadata *slab_info; struct slab_metadata *slab_info;
// slabs with at least one allocated slot and at least one free slot
//
// LIFO doubly-linked list
struct slab_metadata *partial_slabs; struct slab_metadata *partial_slabs;
// slabs without allocated slots that are cached for near-term usage
//
// LIFO singly-linked list
struct slab_metadata *empty_slabs; struct slab_metadata *empty_slabs;
size_t empty_slabs_total; size_t empty_slabs_total; // length * slab_size
struct slab_metadata *free_slabs;
// slabs without allocated slots that are purged and memory protected
//
// FIFO singly-linked list
struct slab_metadata *free_slabs_head;
struct slab_metadata *free_slabs_tail;
struct libdivide_u32_t size_divisor; struct libdivide_u32_t size_divisor;
struct libdivide_u64_t slab_size_divisor; struct libdivide_u64_t slab_size_divisor;
struct random_state rng; struct random_state rng;
@ -319,8 +334,8 @@ static inline void *slab_allocate(size_t requested_size) {
pthread_mutex_unlock(&c->mutex); pthread_mutex_unlock(&c->mutex);
return p; return p;
} else if (c->free_slabs != NULL) { } else if (c->free_slabs_head != NULL) {
struct slab_metadata *metadata = c->free_slabs; struct slab_metadata *metadata = c->free_slabs_head;
void *slab = get_slab(c, slab_size, metadata); void *slab = get_slab(c, slab_size, metadata);
if (requested_size != 0 && memory_protect_rw(slab, slab_size)) { if (requested_size != 0 && memory_protect_rw(slab, slab_size)) {
@ -328,7 +343,10 @@ static inline void *slab_allocate(size_t requested_size) {
return NULL; return NULL;
} }
c->free_slabs = c->free_slabs->next; c->free_slabs_head = c->free_slabs_head->next;
if (c->free_slabs_head == NULL) {
c->free_slabs_tail = NULL;
}
metadata->next = NULL; metadata->next = NULL;
metadata->prev = NULL; metadata->prev = NULL;
@ -392,6 +410,17 @@ static size_t slab_usable_size(void *p) {
return size_classes[slab_size_class(p)]; return size_classes[slab_size_class(p)];
} }
static void enqueue_free_slab(struct size_class *c, struct slab_metadata *metadata) {
metadata->next = NULL;
if (c->free_slabs_tail != NULL) {
c->free_slabs_tail->next = metadata;
} else {
c->free_slabs_head = metadata;
}
c->free_slabs_tail = metadata;
}
static inline void slab_free(void *p) { static inline void slab_free(void *p) {
size_t class = slab_size_class(p); size_t class = slab_size_class(p);
@ -450,8 +479,7 @@ static inline void slab_free(void *p) {
if (c->empty_slabs_total + slab_size > max_empty_slabs_total) { if (c->empty_slabs_total + slab_size > max_empty_slabs_total) {
if (!memory_map_fixed(slab, slab_size)) { if (!memory_map_fixed(slab, slab_size)) {
metadata->next = c->free_slabs; enqueue_free_slab(c, metadata);
c->free_slabs = metadata;
pthread_mutex_unlock(&c->mutex); pthread_mutex_unlock(&c->mutex);
return; return;
} }
@ -1005,8 +1033,7 @@ EXPORT int h_malloc_trim(UNUSED size_t pad) {
iterator = iterator->next; iterator = iterator->next;
c->empty_slabs_total -= slab_size; c->empty_slabs_total -= slab_size;
trimmed->next = c->free_slabs; enqueue_free_slab(c, trimmed);
c->free_slabs = trimmed;
is_trimmed = true; is_trimmed = true;
} }