diff options
Diffstat (limited to 'assoc.c')
| -rw-r--r-- | assoc.c | 35 |
1 files changed, 17 insertions, 18 deletions
@@ -26,7 +26,7 @@ #include <pthread.h> static pthread_cond_t maintenance_cond = PTHREAD_COND_INITIALIZER; - +static pthread_mutex_t maintenance_lock = PTHREAD_MUTEX_INITIALIZER; typedef unsigned long int ub4; /* unsigned 4-byte quantities */ typedef unsigned char ub1; /* unsigned 1-byte quantities */ @@ -147,11 +147,6 @@ static void assoc_start_expand(void) { if (started_expanding) return; - /*With this condition, we can expanding holding only one item lock, - * and it should always be false*/ - if (item_lock_hashpower >= hashpower) - return; - started_expanding = true; pthread_cond_signal(&maintenance_cond); } @@ -209,11 +204,11 @@ int hash_bulk_move = DEFAULT_HASH_BULK_MOVE; static void *assoc_maintenance_thread(void *arg) { + mutex_lock(&maintenance_lock); while (do_run_maintenance_thread) { int ii = 0; - /* As there is only one thread process expanding, and we hold the item - * lock, it seems not necessary to hold the cache_lock . */ + /* There is only one expansion thread, so no need to global lock. */ for (ii = 0; ii < hash_bulk_move && expanding; ++ii) { item *it, *next; int bucket; @@ -223,7 +218,6 @@ static void *assoc_maintenance_thread(void *arg) { * is the lowest N bits of the hv, and the bucket of item_locks is * also the lowest M bits of hv, and N is greater than M. * So we can process expanding with only one item_lock. cool! */ - /*Get item lock for the slot in old hashtable*/ if ((item_lock = item_trylock(expand_bucket))) { for (it = old_hashtable[expand_bucket]; NULL != it; it = next) { next = it->h_next; @@ -247,9 +241,7 @@ static void *assoc_maintenance_thread(void *arg) { } } else { - /*wait for 100ms. since only one expanding thread, it's not - * necessary to sleep a random value*/ - usleep(100*1000); + usleep(10*1000); } if (item_lock) { @@ -260,11 +252,18 @@ static void *assoc_maintenance_thread(void *arg) { if (!expanding) { /* We are done expanding.. just wait for next invocation */ - mutex_lock(&cache_lock); started_expanding = false; - pthread_cond_wait(&maintenance_cond, &cache_lock); + pthread_cond_wait(&maintenance_cond, &maintenance_lock); + /* assoc_expand() swaps out the hash table entirely, so we need + * all threads to not hold any references related to the hash + * table while this happens. + * This is instead of a more complex, possibly slower algorithm to + * allow dynamic hash table expansion without causing significant + * wait times. + */ + pause_threads(PAUSE_ALL_THREADS); assoc_expand(); - mutex_unlock(&cache_lock); + pause_threads(RESUME_ALL_THREADS); } } return NULL; @@ -281,6 +280,7 @@ int start_assoc_maintenance_thread() { hash_bulk_move = DEFAULT_HASH_BULK_MOVE; } } + pthread_mutex_init(&maintenance_lock, NULL); if ((ret = pthread_create(&maintenance_tid, NULL, assoc_maintenance_thread, NULL)) != 0) { fprintf(stderr, "Can't create thread: %s\n", strerror(ret)); @@ -290,13 +290,12 @@ int start_assoc_maintenance_thread() { } void stop_assoc_maintenance_thread() { - mutex_lock(&cache_lock); + mutex_lock(&maintenance_lock); do_run_maintenance_thread = 0; pthread_cond_signal(&maintenance_cond); - mutex_unlock(&cache_lock); + mutex_unlock(&maintenance_lock); /* Wait for the maintenance thread to stop */ pthread_join(maintenance_tid, NULL); } - |