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add basic initial heuristic for freeing slabs

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This commit is contained in:
Daniel Micay 2018-08-30 06:44:58 -04:00
parent 456dfe4154
commit 0f5f2bf6c9
1 changed files with 20 additions and 3 deletions
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23
malloc.c
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@ -168,12 +168,15 @@ static size_t get_slab_size(size_t slots, size_t size) {
return PAGE_CEILING(slots * size); return PAGE_CEILING(slots * size);
} }
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;
struct slab_metadata *partial_slabs; struct slab_metadata *partial_slabs;
struct slab_metadata *empty_slabs; struct slab_metadata *empty_slabs;
size_t empty_slabs_total;
struct slab_metadata *free_slabs; struct slab_metadata *free_slabs;
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;
@ -304,6 +307,7 @@ static inline void *slab_allocate(size_t requested_size) {
if (c->empty_slabs != NULL) { if (c->empty_slabs != NULL) {
struct slab_metadata *metadata = c->empty_slabs; struct slab_metadata *metadata = c->empty_slabs;
c->empty_slabs = c->empty_slabs->next; c->empty_slabs = c->empty_slabs->next;
c->empty_slabs_total -= slab_size;
metadata->next = NULL; metadata->next = NULL;
metadata->prev = NULL; metadata->prev = NULL;
@ -321,7 +325,7 @@ static inline void *slab_allocate(size_t requested_size) {
struct slab_metadata *metadata = c->free_slabs; struct slab_metadata *metadata = c->free_slabs;
void *slab = get_slab(c, slab_size, metadata); void *slab = get_slab(c, slab_size, metadata);
if (memory_protect_rw(slab, slab_size)) { if (requested_size != 0 && memory_protect_rw(slab, slab_size)) {
pthread_mutex_unlock(&c->mutex); pthread_mutex_unlock(&c->mutex);
return NULL; return NULL;
} }
@ -444,9 +448,21 @@ static inline void slab_free(void *p) {
metadata->next->prev = metadata->prev; metadata->next->prev = metadata->prev;
} }
metadata->next = c->empty_slabs;
metadata->prev = NULL; metadata->prev = NULL;
if (c->empty_slabs_total + slab_size > max_empty_slabs_total) {
if (!memory_map_fixed(slab, slab_size)) {
metadata->next = c->free_slabs;
c->free_slabs = metadata;
pthread_mutex_unlock(&c->mutex);
return;
}
// handle out-of-memory by just putting it into the empty slabs list
}
metadata->next = c->empty_slabs;
c->empty_slabs = metadata; c->empty_slabs = metadata;
c->empty_slabs_total += slab_size;
} }
pthread_mutex_unlock(&c->mutex); pthread_mutex_unlock(&c->mutex);
@ -967,7 +983,7 @@ EXPORT int h_mallopt(UNUSED int param, UNUSED int value) {
return 0; return 0;
} }
static const size_t pad_threshold = 16 * 1024 * 1024; static const size_t pad_threshold = max_empty_slabs_total * N_SIZE_CLASSES;
EXPORT int h_malloc_trim(size_t pad) { EXPORT int h_malloc_trim(size_t pad) {
if (pad > pad_threshold) { if (pad > pad_threshold) {
@ -995,6 +1011,7 @@ EXPORT int h_malloc_trim(size_t pad) {
struct slab_metadata *trimmed = iterator; struct slab_metadata *trimmed = iterator;
iterator = iterator->next; iterator = iterator->next;
c->empty_slabs_total -= slab_size;
trimmed->next = c->free_slabs; trimmed->next = c->free_slabs;
c->free_slabs = trimmed; c->free_slabs = trimmed;