Improve logging of autovacuum I/O activity

This adds some I/O stats to the logging of autovacuum (when the
operation takes long enough that log_autovacuum_min_duration causes it
to be logged), so that it is easier to tune.  Notably, it adds buffer
I/O counts (hits, misses, dirtied) and read and write rate.

Authors: Greg Smith and Noah Misch

Author: alvherre

src/backend/commands/vacuum.c

@@ -214,6 +214,9 @@ vacuum(VacuumStmt *vacstmt, Oid relid, bool do_toast,
 
 		VacuumCostActive = (VacuumCostDelay > 0);
 		VacuumCostBalance = 0;
+		VacuumPageHit = 0;
+		VacuumPageMiss = 0;
+		VacuumPageDirty = 0;
 
 		/*
 		 * Loop to process each selected relation.

src/backend/commands/vacuumlazy.c

@@ -155,6 +155,10 @@ lazy_vacuum_rel(Relation onerel, VacuumStmt *vacstmt,
 	BlockNumber possibly_freeable;
 	PGRUsage	ru0;
 	TimestampTz starttime = 0;
+ 	long		secs;
+ 	int			usecs;
+ 	double		read_rate,
+				write_rate;
 	bool		scan_all;
 	TransactionId freezeTableLimit;
 	BlockNumber new_rel_pages;
@@ -166,8 +170,7 @@ lazy_vacuum_rel(Relation onerel, VacuumStmt *vacstmt,
 	if (IsAutoVacuumWorkerProcess() && Log_autovacuum_min_duration >= 0)
 	{
 		pg_rusage_init(&ru0);
-		if (Log_autovacuum_min_duration > 0)
-			starttime = GetCurrentTimestamp();
+		starttime = GetCurrentTimestamp();
 	}
 
 	if (vacstmt->options & VACOPT_VERBOSE)
@@ -262,13 +265,29 @@ lazy_vacuum_rel(Relation onerel, VacuumStmt *vacstmt,
 	/* and log the action if appropriate */
 	if (IsAutoVacuumWorkerProcess() && Log_autovacuum_min_duration >= 0)
 	{
+		TimestampTz	endtime = GetCurrentTimestamp();
+
 		if (Log_autovacuum_min_duration == 0 ||
-			TimestampDifferenceExceeds(starttime, GetCurrentTimestamp(),
+			TimestampDifferenceExceeds(starttime, endtime,
 									   Log_autovacuum_min_duration))
+		{
+			TimestampDifference(starttime, endtime, &secs, &usecs);
+
+			read_rate = 0;
+			write_rate = 0;
+			if ((secs > 0) || (usecs > 0))
+			{
+				read_rate = (double) BLCKSZ * VacuumPageMiss / (1024 * 1024) /
+					(secs + usecs / 1000000.0);
+				write_rate = (double) BLCKSZ * VacuumPageDirty / (1024 * 1024) /
+ 					(secs + usecs / 1000000.0);
+			}
 			ereport(LOG,
 					(errmsg("automatic vacuum of table \"%s.%s.%s\": index scans: %d\n"
 							"pages: %d removed, %d remain\n"
 							"tuples: %.0f removed, %.0f remain\n"
+							"buffer usage: %d hits, %d misses, %d dirtied\n"
+							"avg read rate: %.3f MiB/s, avg write rate: %.3f MiB/s\n"
 							"system usage: %s",
 							get_database_name(MyDatabaseId),
 							get_namespace_name(RelationGetNamespace(onerel)),
@@ -277,8 +296,13 @@ lazy_vacuum_rel(Relation onerel, VacuumStmt *vacstmt,
 							vacrelstats->pages_removed,
 							vacrelstats->rel_pages,
 							vacrelstats->tuples_deleted,
-							new_rel_tuples,
+							vacrelstats->new_rel_tuples,
+							VacuumPageHit,
+							VacuumPageMiss,
+							VacuumPageDirty,
+							read_rate,write_rate,
 							pg_rusage_show(&ru0))));
+		}
 	}
 }
 

src/backend/storage/buffer/bufmgr.c

@@ -340,6 +340,7 @@ ReadBuffer_common(SMgrRelation smgr, char relpersistence, ForkNumber forkNum,
 		{
 			/* Just need to update stats before we exit */
 			*hit = true;
+			VacuumPageHit++;
 
 			if (VacuumCostActive)
 				VacuumCostBalance += VacuumCostPageHit;
@@ -471,6 +472,7 @@ ReadBuffer_common(SMgrRelation smgr, char relpersistence, ForkNumber forkNum,
 		TerminateBufferIO(bufHdr, false, BM_VALID);
 	}
 
+	VacuumPageMiss++;
 	if (VacuumCostActive)
 		VacuumCostBalance += VacuumCostPageMiss;
 
@@ -972,10 +974,14 @@ MarkBufferDirty(Buffer buffer)
 	Assert(bufHdr->refcount > 0);
 
 	/*
-	 * If the buffer was not dirty already, do vacuum cost accounting.
+	 * If the buffer was not dirty already, do vacuum accounting.
 	 */
-	if (!(bufHdr->flags & BM_DIRTY) && VacuumCostActive)
-		VacuumCostBalance += VacuumCostPageDirty;
+	if (!(bufHdr->flags & BM_DIRTY))
+	{
+		VacuumPageDirty++;
+		if (VacuumCostActive)
+			VacuumCostBalance += VacuumCostPageDirty;
+	}
 
 	bufHdr->flags |= (BM_DIRTY | BM_JUST_DIRTIED);
 
@@ -2337,8 +2343,12 @@ SetBufferCommitInfoNeedsSave(Buffer buffer)
 	{
 		LockBufHdr(bufHdr);
 		Assert(bufHdr->refcount > 0);
-		if (!(bufHdr->flags & BM_DIRTY) && VacuumCostActive)
-			VacuumCostBalance += VacuumCostPageDirty;
+		if (!(bufHdr->flags & BM_DIRTY))
+		{
+			VacuumPageDirty++;
+			if (VacuumCostActive)
+				VacuumCostBalance += VacuumCostPageDirty;
+		}
 		bufHdr->flags |= (BM_DIRTY | BM_JUST_DIRTIED);
 		UnlockBufHdr(bufHdr);
 	}

src/backend/utils/init/globals.c

@@ -115,6 +115,10 @@ int			VacuumCostPageDirty = 20;
 int			VacuumCostLimit = 200;
 int			VacuumCostDelay = 0;
 
+int			VacuumPageHit = 0;
+int			VacuumPageMiss = 0;
+int			VacuumPageDirty = 0;
+
 int			VacuumCostBalance = 0;		/* working state for vacuum */
 bool		VacuumCostActive = false;
 

src/include/miscadmin.h

@@ -230,6 +230,10 @@ extern int	VacuumCostPageDirty;
 extern int	VacuumCostLimit;
 extern int	VacuumCostDelay;
 
+extern int	VacuumPageHit;
+extern int	VacuumPageMiss;
+extern int	VacuumPageDirty;
+
 extern int	VacuumCostBalance;
 extern bool VacuumCostActive;