Refactor of ActiveDefrag to reduce latencies

Author: sundb

redis.conf

@@ -2297,6 +2297,11 @@ rdb-save-incremental-fsync yes
 # the main dictionary scan
 # active-defrag-max-scan-fields 1000
 
+# The time spent (in microseconds) of the periodic active defrag process. This
+# affects the latency impact of active defrag on client commands. Smaller numbers
+# will result in less latency impact at the cost of increased defrag overhead.
+# active-defrag-cycle-us 500
+
 # Jemalloc background thread for purging will be enabled by default
 jemalloc-bg-thread yes
 

src/ae.c

@@ -56,7 +56,7 @@ aeEventLoop *aeCreateEventLoop(int setsize) {
     if (eventLoop->events == NULL || eventLoop->fired == NULL) goto err;
     eventLoop->setsize = setsize;
     eventLoop->timeEventHead = NULL;
-    eventLoop->timeEventNextId = 0;
+    eventLoop->timeEventNextId = 1;
     eventLoop->stop = 0;
     eventLoop->maxfd = -1;
     eventLoop->beforesleep = NULL;

src/config.c

@@ -3172,6 +3172,7 @@ standardConfig static_configs[] = {
     createIntConfig("active-defrag-cycle-max", NULL, MODIFIABLE_CONFIG, 1, 99, server.active_defrag_cycle_max, 25, INTEGER_CONFIG, NULL, updateDefragConfiguration), /* Default: 25% CPU max (at upper threshold) */
     createIntConfig("active-defrag-threshold-lower", NULL, MODIFIABLE_CONFIG, 0, 1000, server.active_defrag_threshold_lower, 10, INTEGER_CONFIG, NULL, NULL), /* Default: don't defrag when fragmentation is below 10% */
     createIntConfig("active-defrag-threshold-upper", NULL, MODIFIABLE_CONFIG, 0, 1000, server.active_defrag_threshold_upper, 100, INTEGER_CONFIG, NULL, updateDefragConfiguration), /* Default: maximum defrag force at 100% fragmentation */
+    createIntConfig("active-defrag-cycle-us", NULL, MODIFIABLE_CONFIG, 0, 100000, server.active_defrag_cycle_us, 500, INTEGER_CONFIG, NULL, updateDefragConfiguration),
     createIntConfig("lfu-log-factor", NULL, MODIFIABLE_CONFIG, 0, INT_MAX, server.lfu_log_factor, 10, INTEGER_CONFIG, NULL, NULL),
     createIntConfig("lfu-decay-time", NULL, MODIFIABLE_CONFIG, 0, INT_MAX, server.lfu_decay_time, 1, INTEGER_CONFIG, NULL, NULL),
     createIntConfig("replica-priority", "slave-priority", MODIFIABLE_CONFIG, 0, INT_MAX, server.slave_priority, 100, INTEGER_CONFIG, NULL, NULL),

src/db.c

@@ -2075,8 +2075,6 @@ static void deleteKeyAndPropagate(redisDb *db, robj *keyobj, int notify_type, lo
         keyobj = createStringObject(keyobj->ptr, sdslen(keyobj->ptr));
     }
 
-    serverLog(LL_DEBUG,"key %s %s: deleting it", (char*)keyobj->ptr, notify_type == NOTIFY_EXPIRED ? "expired" : "evicted");
-
     /* We compute the amount of memory freed by db*Delete() alone.
      * It is possible that actually the memory needed to propagate
      * the DEL in AOF and replication link is greater than the one