Add eviction count for table cache lru cleanup (innobase)

This is a port of dveeden's work:

https://github.com/dveeden/mysql-server/commit/e9d00e859e3854bf8f71873caa69c060e670350b

(Mostly changes in linenumbers, a bit of whitespace fix-up.)

storage/innobase/include/srv0mon.h

@@ -378,6 +378,7 @@ enum monitor_id_t {
 	MONITOR_SRV_MEM_VALIDATE_MICROSECOND,
 	MONITOR_SRV_PURGE_MICROSECOND,
 	MONITOR_SRV_DICT_LRU_MICROSECOND,
+	MONITOR_SRV_DICT_LRU_EVICT_COUNT,
 	MONITOR_SRV_CHECKPOINT_MICROSECOND,
 	MONITOR_OVLD_SRV_DBLWR_WRITES,
 	MONITOR_OVLD_SRV_DBLWR_PAGES_WRITTEN,

storage/innobase/srv/srv0mon.cc

@@ -1196,6 +1196,11 @@ static monitor_info_t	innodb_counter_info[] =
 	 MONITOR_NONE,
 	 MONITOR_DEFAULT_START, MONITOR_SRV_DICT_LRU_MICROSECOND},
 
+	{"innodb_dict_lru_count", "server",
+	 "Number of tables evicted from DICT LRU list",
+	 MONITOR_NONE,
+	 MONITOR_DEFAULT_START, MONITOR_SRV_DICT_LRU_EVICT_COUNT},
+
 	{"innodb_checkpoint_usec", "server",
 	 "Time (in microseconds) spent by master thread to do checkpoint",
 	 MONITOR_NONE,

storage/innobase/srv/srv0srv.cc

@@ -2274,6 +2274,7 @@ srv_master_do_active_tasks(void)
 {
 	ib_time_t	cur_time = ut_time();
 	ullint		counter_time = ut_time_us(NULL);
+	ulint		n_evicted = 0;
 
 	/* First do the tasks that we are suppose to do at each
 	invocation of this function. */
@@ -2334,7 +2335,9 @@ srv_master_do_active_tasks(void)
 
 	if (cur_time % SRV_MASTER_DICT_LRU_INTERVAL == 0) {
 		srv_main_thread_op_info = "enforcing dict cache limit";
-		srv_master_evict_from_table_cache(50);
+		n_evicted = srv_master_evict_from_table_cache(50);
+		MONITOR_INC_VALUE(
+			MONITOR_SRV_DICT_LRU_EVICT_COUNT, n_evicted);
 		MONITOR_INC_TIME_IN_MICRO_SECS(
 			MONITOR_SRV_DICT_LRU_MICROSECOND, counter_time);
 	}