refine code, add comments for ossrs.net monitor.

@@ -6,8 +6,13 @@ max_connections     1000;
 heartbeat {
     enabled         on;
     interval        9.3;
+    # for python api-server
     url             http://127.0.0.1:8085/api/v1/servers;
     device_id       "my-srs-device";
+    # for ossrs.net monitor, device_id is the key genereated by bsm.
+    #url             http://www.ossrs.net:1977/api/v1/robots/servers;
+    #device_id       "35c9b402c12a7246868752e2878f7e0e";
+    # with detail summaries
     summaries       on;
 }
 stats {

@@ -682,7 +682,7 @@ int SrsServer::do_cycle()
     // the deamon thread, update the time cache
     while (true) {
         // the interval in config.
-        int heartbeat_max_resolution = (int)(_srs_config->get_heartbeat_interval() / 100);
+        int heartbeat_max_resolution = (int)(_srs_config->get_heartbeat_interval() / SRS_SYS_CYCLE_INTERVAL);
         
         // dynamic fetch the max.
         int __max = max;