Avoid using log_sys mutex when printing out show engine innodb status,

instead peek (maybe) old data.

storage/xtradb/buf/buf0buf.cc

@@ -378,6 +378,48 @@ buf_pool_get_oldest_modification(void)
 	return(oldest_lsn);
 }
 
+/********************************************************************//**
+Gets the smallest oldest_modification lsn for any page in the pool. Returns
+zero if all modified pages have been flushed to disk.
+@return oldest modification in pool, zero if none */
+UNIV_INTERN
+lsn_t
+buf_pool_get_oldest_modification_peek(void)
+/*=======================================*/
+{
+	ulint		i;
+	buf_page_t*	bpage;
+	lsn_t		lsn = 0;
+	lsn_t		oldest_lsn = 0;
+
+	/* Dirsty read to buffer pool array */
+	for (i = 0; i < srv_buf_pool_instances; i++) {
+		buf_pool_t*	buf_pool;
+
+		buf_pool = buf_pool_from_array(i);
+
+		buf_flush_list_mutex_enter(buf_pool);
+
+		bpage = UT_LIST_GET_LAST(buf_pool->flush_list);
+
+		if (bpage != NULL) {
+			ut_ad(bpage->in_flush_list);
+			lsn = bpage->oldest_modification;
+		}
+
+		buf_flush_list_mutex_exit(buf_pool);
+
+		if (!oldest_lsn || oldest_lsn > lsn) {
+			oldest_lsn = lsn;
+		}
+	}
+
+	/* The returned answer may be out of date: the flush_list can
+	change after the mutex has been released. */
+
+	return(oldest_lsn);
+}
+
 /********************************************************************//**
 Get total buffer pool statistics. */
 UNIV_INTERN

storage/xtradb/include/buf0buf.h

@@ -271,6 +271,15 @@ lsn_t
 buf_pool_get_oldest_modification(void);
 /*==================================*/
 
+/********************************************************************//**
+Gets the smallest oldest_modification lsn for any page in the pool. Returns
+zero if all modified pages have been flushed to disk.
+@return oldest modification in pool, zero if none */
+UNIV_INTERN
+lsn_t
+buf_pool_get_oldest_modification_peek(void);
+/*=======================================*/
+
 /********************************************************************//**
 Allocates a buf_page_t descriptor. This function must succeed. In case
 of failure we assert in this function. */

storage/xtradb/include/log0log.h

@@ -633,6 +633,15 @@ UNIV_INLINE
 lsn_t
 log_get_tracked_lsn(void);
 /*=====================*/
+/****************************************************************//**
+Unsafely reads the log_sys->tracked_lsn value.  Uses atomic operations
+if available, or use dirty read. Use for printing only.
+
+@return log_sys->tracked_lsn value. */
+UNIV_INLINE
+lsn_t
+log_get_tracked_lsn_peek(void);
+/*==========================*/
 
 extern log_t*	log_sys;
 

storage/xtradb/include/log0log.ic

@@ -552,12 +552,28 @@ log_free_check(void)
 }
 #endif /* !UNIV_HOTBACKUP */
 
+/****************************************************************//**
+Unsafely reads the log_sys->tracked_lsn value.  Uses atomic operations
+if available, or use dirty read. Use for printing only.
+
+@return log_sys->tracked_lsn value. */
+UNIV_INLINE
+lsn_t
+log_get_tracked_lsn_peek(void)
+/*==========================*/
+{
+#ifdef HAVE_ATOMIC_BUILTINS_64
+	return os_atomic_increment_uint64(&log_sys->tracked_lsn, 0);
+#else
+	return log_sys->tracked_lsn;
+#endif
+}
+
 /****************************************************************//**
 Safely reads the log_sys->tracked_lsn value.  Uses atomic operations
 if available, otherwise this field is protected with the log system
 mutex.  The writer counterpart function is log_set_tracked_lsn() in
 log0online.c.
-
 @return log_sys->tracked_lsn value. */
 UNIV_INLINE
 lsn_t
@@ -571,4 +587,3 @@ log_get_tracked_lsn(void)
 	return log_sys->tracked_lsn;
 #endif
 }
-

storage/xtradb/log/log0log.cc

@@ -196,6 +196,27 @@ log_buf_pool_get_oldest_modification(void)
 	return(lsn);
 }
 
+/****************************************************************//**
+Returns the oldest modified block lsn in the pool, or log_sys->lsn if none
+exists.
+@return	LSN of oldest modification */
+static
+lsn_t
+log_buf_pool_get_oldest_modification_peek(void)
+/*===========================================*/
+{
+	lsn_t	lsn;
+
+	lsn = buf_pool_get_oldest_modification_peek();
+
+	if (!lsn) {
+
+		lsn = log_sys->lsn;
+	}
+
+	return(lsn);
+}
+
 /****************************************************************//**
 Checks if the log groups have a big enough margin of free space in
 so that a new log entry can be written without overwriting log data
@@ -3875,7 +3896,7 @@ log_print(
 	double	time_elapsed;
 	time_t	current_time;
 
-	mutex_enter(&(log_sys->mutex));
+	// mutex_enter(&(log_sys->mutex));
 
 	fprintf(file,
 		"Log sequence number " LSN_PF "\n"
@@ -3884,7 +3905,7 @@ log_print(
 		"Last checkpoint at  " LSN_PF "\n",
 		log_sys->lsn,
 		log_sys->flushed_to_disk_lsn,
-		log_buf_pool_get_oldest_modification(),
+		log_buf_pool_get_oldest_modification_peek(),
 		log_sys->last_checkpoint_lsn);
 
 	fprintf(file,
@@ -3894,7 +3915,7 @@ log_print(
 		"Checkpoint age        " LSN_PF "\n",
 		log_sys->max_checkpoint_age,
 		log_sys->max_checkpoint_age_async,
-		log_sys->lsn -log_buf_pool_get_oldest_modification(),
+		log_sys->lsn -log_buf_pool_get_oldest_modification_peek(),
 		log_sys->lsn - log_sys->last_checkpoint_lsn);
 
 	current_time = time(NULL);
@@ -3923,14 +3944,14 @@ log_print(
 			"Log tracking enabled\n"
 			"Log tracked up to   " LSN_PF "\n"
 			"Max tracked LSN age " LSN_PF "\n",
-			log_get_tracked_lsn(),
+			log_get_tracked_lsn_peek(),
 			log_sys->max_checkpoint_age);
 	}
 
 	log_sys->n_log_ios_old = log_sys->n_log_ios;
 	log_sys->last_printout_time = current_time;
 
-	mutex_exit(&(log_sys->mutex));
+	//mutex_exit(&(log_sys->mutex));
 }
 
 /**********************************************************************//**