MDEV-13670/MDEV-14550 Error log flood : "InnoDB: page_cleaner: 1000ms...

MDEV-13670/MDEV-14550 Error log flood :  "InnoDB: page_cleaner: 1000ms intended loop took N ms. The settings might not be optimal."

Silence the error log output that was introduced in MySQL 5.7
(MariaDB 10.2.2) if log_warnings=2 or less.

We should still figure out what these messages really indicate
and how to solve the problems.

pc_sleep_if_needed(): Add a parameter for the current time,
so that there will be fewer successive calls to ut_time_ms()
with no I/O between them.

buf_flush_page_cleaner_coordinator(): Exit the first loop
whenever shutdown has been requested. At the start of the loop,
call ut_time_ms() only once. Do not display the message if
log_warnings=2 or less.

storage/innobase/buf/buf0flu.cc

@@ -28,6 +28,7 @@ Created 11/11/1995 Heikki Tuuri
 #include "ha_prototypes.h"
 #include <mysql/service_thd_wait.h>
 #include <my_dbug.h>
+#include <sql_class.h>
 
 #include "buf0flu.h"
 #include "buf0buf.h"
@@ -2690,21 +2691,21 @@ than a second
 @retval OS_SYNC_TIME_EXCEEDED if timeout was exceeded
 @param next_loop_time	time when next loop iteration should start
 @param sig_count	zero or the value returned by previous call of
-			os_event_reset() */
+			os_event_reset()
+@param cur_time		current time as in ut_time_ms() */
 static
 ulint
 pc_sleep_if_needed(
 /*===============*/
 	ulint		next_loop_time,
-	int64_t		sig_count)
+	int64_t		sig_count,
+	ulint		cur_time)
 {
 	/* No sleep if we are cleaning the buffer pool during the shutdown
 	with everything else finished */
 	if (srv_shutdown_state == SRV_SHUTDOWN_FLUSH_PHASE)
 		return OS_SYNC_TIME_EXCEEDED;
 
-	ulint	cur_time = ut_time_ms();
-
 	if (next_loop_time > cur_time) {
 		/* Get sleep interval in micro seconds. We use
 		ut_min() to avoid long sleep in case of wrap around. */
@@ -3200,6 +3201,7 @@ DECLARE_THREAD(buf_flush_page_cleaner_coordinator)(void*)
 	ulint	last_pages = 0;
 
 	while (srv_shutdown_state == SRV_SHUTDOWN_NONE) {
+		ulint	curr_time = ut_time_ms();
 
 		/* The page_cleaner skips sleep if the server is
 		idle and there are no pending IOs in the buffer pool
@@ -3209,23 +3211,22 @@ DECLARE_THREAD(buf_flush_page_cleaner_coordinator)(void*)
 		    || n_flushed == 0) {
 
 			ret_sleep = pc_sleep_if_needed(
-				next_loop_time, sig_count);
-
-			if (srv_shutdown_state != SRV_SHUTDOWN_NONE) {
-				break;
-			}
-		} else if (ut_time_ms() > next_loop_time) {
+				next_loop_time, sig_count, curr_time);
+		} else if (curr_time > next_loop_time) {
 			ret_sleep = OS_SYNC_TIME_EXCEEDED;
 		} else {
 			ret_sleep = 0;
 		}
 
+		if (srv_shutdown_state != SRV_SHUTDOWN_NONE) {
+			break;
+		}
+
 		sig_count = os_event_reset(buf_flush_event);
 
 		if (ret_sleep == OS_SYNC_TIME_EXCEEDED) {
-			ulint	curr_time = ut_time_ms();
-
-			if (curr_time > next_loop_time + 3000
+			if (global_system_variables.log_warnings > 2
+			    && curr_time > next_loop_time + 3000
 			    && !(test_flags & TEST_SIGINT)) {
 				if (warn_count == 0) {
 					ib::info() << "page_cleaner: 1000ms"