MDEV-25085: Simplify instrumentation for LRU eviction

Let us add the status variable innodb_buffer_pool_pages_LRU_freed
to monitor the number of pages that were freed by a buffer pool LRU
eviction scan, without flushing.

Also, let us simplify the monitor interface:
MONITOR_LRU_BATCH_FLUSH_COUNT, MONITOR_LRU_BATCH_FLUSH_PAGES,
MONITOR_LRU_BATCH_EVICT_COUNT, MONITOR_LRU_BATCH_EVICT_PAGES:
Remove.

MONITOR_LRU_BATCH_FLUSH_TOTAL_PAGE: Track buf_lru_flush_page_count
(innodb_buffer_pool_pages_LRU_flushed).

MONITOR_LRU_BATCH_EVICT_TOTAL_PAGE: Track buf_lru_freed_page_count
(buffer_pool_pages_LRU_freed).

Reviewed by: Vladislav Vaintroub

mysql-test/suite/innodb/r/innodb_skip_innodb_is_tables.result

@@ -110,12 +110,8 @@ buffer_flush_background_pages	buffer	0	NULL	NULL	NULL	0	NULL	NULL	NULL	NULL	NULL
 buffer_LRU_batch_scanned	buffer	0	NULL	NULL	NULL	0	NULL	NULL	NULL	NULL	NULL	NULL	NULL	0	set_owner	Total pages scanned as part of LRU batch
 buffer_LRU_batch_num_scan	buffer	0	NULL	NULL	NULL	0	NULL	NULL	NULL	NULL	NULL	NULL	NULL	0	set_member	Number of times LRU batch is called
 buffer_LRU_batch_scanned_per_call	buffer	0	NULL	NULL	NULL	0	NULL	NULL	NULL	NULL	NULL	NULL	NULL	0	set_member	Pages scanned per LRU batch call
-buffer_LRU_batch_flush_total_pages	buffer	0	NULL	NULL	NULL	0	NULL	NULL	NULL	NULL	NULL	NULL	NULL	0	set_owner	Total pages flushed as part of LRU batches
-buffer_LRU_batches_flush	buffer	0	NULL	NULL	NULL	0	NULL	NULL	NULL	NULL	NULL	NULL	NULL	0	set_member	Number of LRU batches
-buffer_LRU_batch_flush_pages	buffer	0	NULL	NULL	NULL	0	NULL	NULL	NULL	NULL	NULL	NULL	NULL	0	set_member	Pages queued as an LRU batch
-buffer_LRU_batch_evict_total_pages	buffer	0	NULL	NULL	NULL	0	NULL	NULL	NULL	NULL	NULL	NULL	NULL	0	set_owner	Total pages evicted as part of LRU batches
-buffer_LRU_batches_evict	buffer	0	NULL	NULL	NULL	0	NULL	NULL	NULL	NULL	NULL	NULL	NULL	0	set_member	Number of LRU batches
-buffer_LRU_batch_evict_pages	buffer	0	NULL	NULL	NULL	0	NULL	NULL	NULL	NULL	NULL	NULL	NULL	0	set_member	Pages queued as an LRU batch
+buffer_LRU_batch_flush_total_pages	buffer	0	NULL	NULL	NULL	0	NULL	NULL	NULL	NULL	NULL	NULL	NULL	0	status_counter	Total pages flushed as part of LRU batches
+buffer_LRU_batch_evict_total_pages	buffer	0	NULL	NULL	NULL	0	NULL	NULL	NULL	NULL	NULL	NULL	NULL	0	status_counter	Total pages evicted as part of LRU batches
 buffer_LRU_single_flush_failure_count	Buffer	0	NULL	NULL	NULL	0	NULL	NULL	NULL	NULL	NULL	NULL	NULL	0	counter	Number of times attempt to flush a single page from LRU failed
 buffer_LRU_get_free_search	Buffer	0	NULL	NULL	NULL	0	NULL	NULL	NULL	NULL	NULL	NULL	NULL	0	counter	Number of searches performed for a clean page
 buffer_LRU_search_scanned	buffer	0	NULL	NULL	NULL	0	NULL	NULL	NULL	NULL	NULL	NULL	NULL	0	set_owner	Total pages scanned as part of LRU search

mysql-test/suite/innodb/r/innodb_status_variables.result

@@ -22,6 +22,7 @@ INNODB_BUFFER_POOL_PAGES_MISC
 INNODB_BUFFER_POOL_PAGES_OLD
 INNODB_BUFFER_POOL_PAGES_TOTAL
 INNODB_BUFFER_POOL_PAGES_LRU_FLUSHED
+INNODB_BUFFER_POOL_PAGES_LRU_FREED
 INNODB_BUFFER_POOL_READ_AHEAD_RND
 INNODB_BUFFER_POOL_READ_AHEAD
 INNODB_BUFFER_POOL_READ_AHEAD_EVICTED

mysql-test/suite/innodb/r/monitor.result

@@ -77,11 +77,7 @@ buffer_LRU_batch_scanned	disabled
 buffer_LRU_batch_num_scan	disabled
 buffer_LRU_batch_scanned_per_call	disabled
 buffer_LRU_batch_flush_total_pages	disabled
-buffer_LRU_batches_flush	disabled
-buffer_LRU_batch_flush_pages	disabled
 buffer_LRU_batch_evict_total_pages	disabled
-buffer_LRU_batches_evict	disabled
-buffer_LRU_batch_evict_pages	disabled
 buffer_LRU_single_flush_failure_count	disabled
 buffer_LRU_get_free_search	disabled
 buffer_LRU_search_scanned	disabled

storage/innobase/buf/buf0buf.cc

@@ -1717,19 +1717,11 @@ inline bool buf_pool_t::withdraw_blocks()
 
 		/* reserve free_list length */
 		if (UT_LIST_GET_LEN(withdraw) < withdraw_target) {
-			ulint n_flushed = buf_flush_lists(
+			buf_flush_lists(
 				std::max<ulint>(withdraw_target
 						- UT_LIST_GET_LEN(withdraw),
 						srv_LRU_scan_depth), 0);
 			buf_flush_wait_batch_end_acquiring_mutex(true);
-
-			if (n_flushed) {
-				MONITOR_INC_VALUE_CUMULATIVE(
-					MONITOR_LRU_BATCH_FLUSH_TOTAL_PAGE,
-					MONITOR_LRU_BATCH_FLUSH_COUNT,
-					MONITOR_LRU_BATCH_FLUSH_PAGES,
-					n_flushed);
-			}
 		}
 
 		/* relocate blocks/buddies in withdrawn area */

storage/innobase/buf/buf0flu.cc

@@ -57,6 +57,9 @@ Created 11/11/1995 Heikki Tuuri
 Also included in buf_flush_page_count. */
 ulint buf_lru_flush_page_count;
 
+/** Number of pages freed without flushing. Protected by buf_pool.mutex. */
+ulint buf_lru_freed_page_count;
+
 /** Number of pages flushed. Protected by buf_pool.mutex. */
 ulint buf_flush_page_count;
 
@@ -1347,13 +1350,6 @@ static void buf_flush_LRU_list_batch(ulint max, flush_counters_t *n)
   if (space)
     space->release();
 
-  /* We keep track of all flushes happening as part of LRU flush. When
-  estimating the desired rate at which flush_list should be flushed,
-  we factor in this value. */
-  buf_lru_flush_page_count+= n->flushed;
-
-  mysql_mutex_assert_owner(&buf_pool.mutex);
-
   if (scanned)
     MONITOR_INC_VALUE_CUMULATIVE(MONITOR_LRU_BATCH_SCANNED,
                                  MONITOR_LRU_BATCH_SCANNED_NUM_CALL,
@@ -1374,14 +1370,13 @@ static ulint buf_do_LRU_batch(ulint max)
   n.flushed= 0;
   n.evicted= n_unzip_LRU_evicted;
   buf_flush_LRU_list_batch(max, &n);
+  mysql_mutex_assert_owner(&buf_pool.mutex);
 
   if (const ulint evicted= n.evicted - n_unzip_LRU_evicted)
-  {
-    MONITOR_INC_VALUE_CUMULATIVE(MONITOR_LRU_BATCH_EVICT_TOTAL_PAGE,
-                                 MONITOR_LRU_BATCH_EVICT_COUNT,
-                                 MONITOR_LRU_BATCH_EVICT_PAGES,
-                                 evicted);
-  }
+    buf_lru_freed_page_count+= evicted;
+
+  if (n.flushed)
+    buf_lru_flush_page_count+= n.flushed;
 
   return n.flushed;
 }

storage/innobase/handler/ha_innodb.cc

@@ -950,6 +950,7 @@ static SHOW_VAR innodb_status_variables[]= {
   {"buffer_pool_pages_total",
    &export_vars.innodb_buffer_pool_pages_total, SHOW_SIZE_T},
   {"buffer_pool_pages_LRU_flushed", &buf_lru_flush_page_count, SHOW_SIZE_T},
+  {"buffer_pool_pages_LRU_freed", &buf_lru_freed_page_count, SHOW_SIZE_T},
   {"buffer_pool_read_ahead_rnd",
    &export_vars.innodb_buffer_pool_read_ahead_rnd, SHOW_SIZE_T},
   {"buffer_pool_read_ahead",

storage/innobase/include/buf0flu.h

@@ -36,6 +36,8 @@ extern ulint buf_flush_page_count;
 /** Number of pages flushed via LRU. Protected by buf_pool.mutex.
 Also included in buf_flush_page_count. */
 extern ulint buf_lru_flush_page_count;
+/** Number of pages freed without flushing. Protected by buf_pool.mutex. */
+extern ulint buf_lru_freed_page_count;
 
 /** Flag indicating if the page_cleaner is in active state. */
 extern bool buf_page_cleaner_is_active;

storage/innobase/include/srv0mon.h

@@ -220,11 +220,7 @@ enum monitor_id_t {
 	MONITOR_LRU_BATCH_SCANNED_NUM_CALL,
 	MONITOR_LRU_BATCH_SCANNED_PER_CALL,
 	MONITOR_LRU_BATCH_FLUSH_TOTAL_PAGE,
-	MONITOR_LRU_BATCH_FLUSH_COUNT,
-	MONITOR_LRU_BATCH_FLUSH_PAGES,
 	MONITOR_LRU_BATCH_EVICT_TOTAL_PAGE,
-	MONITOR_LRU_BATCH_EVICT_COUNT,
-	MONITOR_LRU_BATCH_EVICT_PAGES,
 	MONITOR_LRU_SINGLE_FLUSH_FAILURE_COUNT,
 	MONITOR_LRU_GET_FREE_SEARCH,
 	MONITOR_LRU_SEARCH_SCANNED,

storage/innobase/srv/srv0mon.cc

@@ -495,34 +495,16 @@ static monitor_info_t	innodb_counter_info[] =
 	/* Cumulative counter for LRU batch pages flushed */
 	{"buffer_LRU_batch_flush_total_pages", "buffer",
 	 "Total pages flushed as part of LRU batches",
-	 MONITOR_SET_OWNER, MONITOR_LRU_BATCH_FLUSH_COUNT,
-	 MONITOR_LRU_BATCH_FLUSH_TOTAL_PAGE},
-
-	{"buffer_LRU_batches_flush", "buffer",
-	 "Number of LRU batches",
-	 MONITOR_SET_MEMBER, MONITOR_LRU_BATCH_FLUSH_TOTAL_PAGE,
-	 MONITOR_LRU_BATCH_FLUSH_COUNT},
-
-	{"buffer_LRU_batch_flush_pages", "buffer",
-	 "Pages queued as an LRU batch",
-	 MONITOR_SET_MEMBER, MONITOR_LRU_BATCH_FLUSH_TOTAL_PAGE,
-	 MONITOR_LRU_BATCH_FLUSH_PAGES},
+	 static_cast<monitor_type_t>(
+	 MONITOR_EXISTING | MONITOR_DEFAULT_ON),
+	 MONITOR_DEFAULT_START, MONITOR_LRU_BATCH_FLUSH_TOTAL_PAGE},
 
 	/* Cumulative counter for LRU batch pages flushed */
 	{"buffer_LRU_batch_evict_total_pages", "buffer",
 	 "Total pages evicted as part of LRU batches",
-	 MONITOR_SET_OWNER, MONITOR_LRU_BATCH_EVICT_COUNT,
-	 MONITOR_LRU_BATCH_EVICT_TOTAL_PAGE},
-
-	{"buffer_LRU_batches_evict", "buffer",
-	 "Number of LRU batches",
-	 MONITOR_SET_MEMBER, MONITOR_LRU_BATCH_EVICT_TOTAL_PAGE,
-	 MONITOR_LRU_BATCH_EVICT_COUNT},
-
-	{"buffer_LRU_batch_evict_pages", "buffer",
-	 "Pages queued as an LRU batch",
-	 MONITOR_SET_MEMBER, MONITOR_LRU_BATCH_EVICT_TOTAL_PAGE,
-	 MONITOR_LRU_BATCH_EVICT_PAGES},
+	 static_cast<monitor_type_t>(
+	 MONITOR_EXISTING | MONITOR_DEFAULT_ON),
+	 MONITOR_DEFAULT_START, MONITOR_LRU_BATCH_EVICT_TOTAL_PAGE},
 
 	{"buffer_LRU_single_flush_failure_count", "Buffer",
 	 "Number of times attempt to flush a single page from LRU failed",
@@ -1575,6 +1557,14 @@ srv_mon_process_existing_counter(
 		value = srv_stats.non_index_pages_written;
 		break;
 
+	case MONITOR_LRU_BATCH_FLUSH_TOTAL_PAGE:
+		value = buf_lru_flush_page_count;
+		break;
+
+	case MONITOR_LRU_BATCH_EVICT_TOTAL_PAGE:
+		value = buf_lru_freed_page_count;
+		break;
+
 	/* innodb_pages_read */
 	case MONITOR_OVLD_PAGES_READ:
 		value = buf_pool.stat.n_pages_read;

storage/rocksdb/mysql-test/rocksdb/r/innodb_i_s_tables_disabled.result

@@ -92,12 +92,8 @@ buffer_flush_background_pages	buffer	0	NULL	NULL	NULL	0	NULL	NULL	NULL	NULL	NULL
 buffer_LRU_batch_scanned	buffer	0	NULL	NULL	NULL	0	NULL	NULL	NULL	NULL	NULL	NULL	NULL	0	set_owner	Total pages scanned as part of LRU batch
 buffer_LRU_batch_num_scan	buffer	0	NULL	NULL	NULL	0	NULL	NULL	NULL	NULL	NULL	NULL	NULL	0	set_member	Number of times LRU batch is called
 buffer_LRU_batch_scanned_per_call	buffer	0	NULL	NULL	NULL	0	NULL	NULL	NULL	NULL	NULL	NULL	NULL	0	set_member	Pages scanned per LRU batch call
-buffer_LRU_batch_flush_total_pages	buffer	0	NULL	NULL	NULL	0	NULL	NULL	NULL	NULL	NULL	NULL	NULL	0	set_owner	Total pages flushed as part of LRU batches
-buffer_LRU_batches_flush	buffer	0	NULL	NULL	NULL	0	NULL	NULL	NULL	NULL	NULL	NULL	NULL	0	set_member	Number of LRU batches
-buffer_LRU_batch_flush_pages	buffer	0	NULL	NULL	NULL	0	NULL	NULL	NULL	NULL	NULL	NULL	NULL	0	set_member	Pages queued as an LRU batch
-buffer_LRU_batch_evict_total_pages	buffer	0	NULL	NULL	NULL	0	NULL	NULL	NULL	NULL	NULL	NULL	NULL	0	set_owner	Total pages evicted as part of LRU batches
-buffer_LRU_batches_evict	buffer	0	NULL	NULL	NULL	0	NULL	NULL	NULL	NULL	NULL	NULL	NULL	0	set_member	Number of LRU batches
-buffer_LRU_batch_evict_pages	buffer	0	NULL	NULL	NULL	0	NULL	NULL	NULL	NULL	NULL	NULL	NULL	0	set_member	Pages queued as an LRU batch
+buffer_LRU_batch_flush_total_pages	buffer	0	NULL	NULL	NULL	0	NULL	NULL	NULL	NULL	NULL	NULL	NULL	0	status_counter	Total pages flushed as part of LRU batches
+buffer_LRU_batch_evict_total_pages	buffer	0	NULL	NULL	NULL	0	NULL	NULL	NULL	NULL	NULL	NULL	NULL	0	status_counter	Total pages evicted as part of LRU batches
 buffer_LRU_single_flush_failure_count	Buffer	0	NULL	NULL	NULL	0	NULL	NULL	NULL	NULL	NULL	NULL	NULL	0	counter	Number of times attempt to flush a single page from LRU failed
 buffer_LRU_get_free_search	Buffer	0	NULL	NULL	NULL	0	NULL	NULL	NULL	NULL	NULL	NULL	NULL	0	counter	Number of searches performed for a clean page
 buffer_LRU_search_scanned	buffer	0	NULL	NULL	NULL	0	NULL	NULL	NULL	NULL	NULL	NULL	NULL	0	set_owner	Total pages scanned as part of LRU search