Cleanup: MONITOR_EXISTING trx_undo_slots_used, trx_undo_slots_cached

Let us remove explicit updates of MONITOR_NUM_UNDO_SLOT_USED
and MONITOR_NUM_UNDO_SLOT_CACHED, and let us compute the rough values
from trx_sys.rseg_array[] on demand.

4 files changed, 29 insertions, 18 deletions

diff --git a/storage/innobase/srv/srv0mon.cc b/storage/innobase/srv/srv0mon.cc
index b6496d03908..2a3720641bc 100644
--- a/storage/innobase/srv/srv0mon.cc
+++ b/storage/innobase/srv/srv0mon.cc
@@ -704,16 +704,18 @@ static monitor_info_t	innodb_counter_info[] =
 	{"trx_rseg_history_len", "transaction",
 	 "Length of the TRX_RSEG_HISTORY list",
 	 static_cast<monitor_type_t>(
-	 MONITOR_EXISTING | MONITOR_DISPLAY_CURRENT | MONITOR_DEFAULT_ON),
+	 MONITOR_EXISTING | MONITOR_DISPLAY_CURRENT),
 	 MONITOR_DEFAULT_START, MONITOR_RSEG_HISTORY_LEN},
 
 	{"trx_undo_slots_used", "transaction", "Number of undo slots used",
-	 MONITOR_NONE,
+	 static_cast<monitor_type_t>(
+	 MONITOR_EXISTING | MONITOR_DISPLAY_CURRENT),
 	 MONITOR_DEFAULT_START, MONITOR_NUM_UNDO_SLOT_USED},
 
 	{"trx_undo_slots_cached", "transaction",
 	 "Number of undo slots cached",
-	 MONITOR_NONE,
+	 static_cast<monitor_type_t>(
+	 MONITOR_EXISTING | MONITOR_DISPLAY_CURRENT | MONITOR_DEFAULT_ON),
 	 MONITOR_DEFAULT_START, MONITOR_NUM_UNDO_SLOT_CACHED},
 
 	{"trx_rseg_current_size", "transaction",
@@ -1383,6 +1385,24 @@ TPOOL_SUPPRESS_TSAN static ulint srv_mon_get_rseg_size()
   return size;
 }
 
+/** @return number of used undo log slots */
+TPOOL_SUPPRESS_TSAN static ulint srv_mon_get_rseg_used()
+{
+  ulint size= 0;
+  for (const auto &rseg : trx_sys.rseg_array)
+    size+= UT_LIST_GET_LEN(rseg.undo_list);
+  return size;
+}
+
+/** @return number of cached undo log slots */
+TPOOL_SUPPRESS_TSAN static ulint srv_mon_get_rseg_cached()
+{
+  ulint size= 0;
+  for (const auto &rseg : trx_sys.rseg_array)
+    size+= UT_LIST_GET_LEN(rseg.undo_cached);
+  return size;
+}
+
 /****************************************************************//**
 This function consolidates some existing server counters used
 by "system status variables". These existing system variables do not have
@@ -1690,7 +1710,12 @@ srv_mon_process_existing_counter(
 	case MONITOR_RSEG_CUR_SIZE:
 		value = srv_mon_get_rseg_size();
 		break;
-
+	case MONITOR_NUM_UNDO_SLOT_USED:
+		value = srv_mon_get_rseg_used();
+		break;
+	case MONITOR_NUM_UNDO_SLOT_CACHED:
+		value = srv_mon_get_rseg_cached();
+		break;
 	case MONITOR_OVLD_N_FILE_OPENED:
 		value = fil_system.n_open;
 		break;
@@ -1812,7 +1837,6 @@ srv_mon_process_existing_counter(
 	case MONITOR_TIMEOUT:
 		value = lock_sys.timeouts;
 		break;
-
 	default:
 		ut_error;
 	}
diff --git a/storage/innobase/trx/trx0purge.cc b/storage/innobase/trx/trx0purge.cc
index 4a2fa214b37..7a63b1155b6 100644
--- a/storage/innobase/trx/trx0purge.cc
+++ b/storage/innobase/trx/trx0purge.cc
@@ -280,8 +280,6 @@ trx_purge_add_undo_to_history(const trx_t* trx, trx_undo_t*& undo, mtr_t* mtr)
 			    TRX_RSEG + TRX_RSEG_UNDO_SLOTS
 			    + undo->id * TRX_RSEG_SLOT_SIZE, 4, 0xff);
 
-		MONITOR_DEC(MONITOR_NUM_UNDO_SLOT_USED);
-
 		uint32_t hist_size = mach_read_from_4(
 			TRX_RSEG_HISTORY_SIZE + TRX_RSEG
 			+ rseg_header->page.frame);
@@ -363,7 +361,6 @@ trx_purge_add_undo_to_history(const trx_t* trx, trx_undo_t*& undo, mtr_t* mtr)
 
 	if (undo->state == TRX_UNDO_CACHED) {
 		UT_LIST_ADD_FIRST(rseg->undo_cached, undo);
-		MONITOR_INC(MONITOR_NUM_UNDO_SLOT_CACHED);
 	} else {
 		ut_ad(undo->state == TRX_UNDO_TO_PURGE);
 		ut_free(undo);
@@ -526,8 +523,6 @@ loop:
       mtr.write<8,mtr_t::MAYBE_NOP>(*rseg_hdr, TRX_RSEG + TRX_RSEG_MAX_TRX_ID +
                                     rseg_hdr->page.frame,
                                     trx_sys.get_max_trx_id() - 1);
-      MONITOR_DEC(MONITOR_NUM_UNDO_SLOT_CACHED);
-      MONITOR_DEC(MONITOR_NUM_UNDO_SLOT_USED);
       goto free_segment;
     }
   }
diff --git a/storage/innobase/trx/trx0rseg.cc b/storage/innobase/trx/trx0rseg.cc
index 6d95dcf06f1..0d7b96e9280 100644
--- a/storage/innobase/trx/trx0rseg.cc
+++ b/storage/innobase/trx/trx0rseg.cc
@@ -394,7 +394,6 @@ void trx_rseg_t::reinit(uint32_t page)
   {
     next= UT_LIST_GET_NEXT(undo_list, undo);
     UT_LIST_REMOVE(undo_cached, undo);
-    MONITOR_DEC(MONITOR_NUM_UNDO_SLOT_CACHED);
     ut_free(undo);
   }
 
@@ -425,7 +424,6 @@ static dberr_t trx_undo_lists_init(trx_rseg_t *rseg,
       if (!undo)
         return DB_CORRUPTION;
       rseg->curr_size+= undo->size;
-      MONITOR_INC(MONITOR_NUM_UNDO_SLOT_USED);
     }
   }
 
diff --git a/storage/innobase/trx/trx0undo.cc b/storage/innobase/trx/trx0undo.cc
index 33b1f93ff65..bccb6538e63 100644
--- a/storage/innobase/trx/trx0undo.cc
+++ b/storage/innobase/trx/trx0undo.cc
@@ -535,8 +535,6 @@ trx_undo_seg_create(fil_space_t *space, buf_block_t *rseg_hdr, ulint *id,
 		      + slot_no * TRX_RSEG_SLOT_SIZE + rseg_hdr->page.frame,
 		      block->page.id().page_no());
 
-	MONITOR_INC(MONITOR_NUM_UNDO_SLOT_USED);
-
 	*err = DB_SUCCESS;
 	return block;
 }
@@ -996,7 +994,6 @@ static void trx_undo_seg_free(const trx_undo_t *undo)
         static_assert(FIL_NULL == 0xffffffff, "compatibility");
         mtr.memset(rseg_header, TRX_RSEG + TRX_RSEG_UNDO_SLOTS +
                    undo->id * TRX_RSEG_SLOT_SIZE, 4, 0xff);
-        MONITOR_DEC(MONITOR_NUM_UNDO_SLOT_USED);
       }
     }
 
@@ -1155,7 +1152,6 @@ corrupted_type:
 		UT_LIST_ADD_LAST(rseg->undo_list, undo);
 	} else {
 		UT_LIST_ADD_LAST(rseg->undo_cached, undo);
-		MONITOR_INC(MONITOR_NUM_UNDO_SLOT_CACHED);
 	}
 
 	mtr.commit();
@@ -1333,7 +1329,6 @@ trx_undo_reuse_cached(trx_t* trx, trx_rseg_t* rseg, trx_undo_t** pundo,
 	}
 
 	UT_LIST_REMOVE(rseg->undo_cached, undo);
-	MONITOR_DEC(MONITOR_NUM_UNDO_SLOT_CACHED);
 
 	*pundo = undo;
 
@@ -1546,7 +1541,6 @@ void trx_undo_commit_cleanup(trx_undo_t *undo)
 
 	if (undo->state == TRX_UNDO_CACHED) {
 		UT_LIST_ADD_FIRST(rseg->undo_cached, undo);
-		MONITOR_INC(MONITOR_NUM_UNDO_SLOT_CACHED);
 		undo = nullptr;
 	} else {
 		ut_ad(undo->state == TRX_UNDO_TO_PURGE);