Make pg_stat_io count IOs as bytes instead of blocks for some operations

Currently in pg_stat_io view, IOs are counted as blocks of size
BLCKSZ.  There are two limitations with this design:
* The actual number of I/O requests sent to the kernel is lower because
I/O requests may be merged before being sent.  Additionally, it gives
the impression that all I/Os are done in block size, which shadows the
benefits of merging I/O requests.
* Some patches are under work to extend pg_stat_io for the tracking of
operations that may not be linked to the block size.  For example, WAL
read IOs are done in variable bytes and it is not possible to correctly
show these IOs in pg_stat_io view, and we want to keep all this data in
a single system view rather than spread it across multiple relations to
ease monitoring.

WaitReadBuffers() can now be tracked as a single read operation
worth N blocks.  Same for ExtendBufferedRelShared() and
ExtendBufferedRelLocal() for extensions.

Three columns are added to pg_stat_io for reads, writes and extensions
for the byte calculations.  op_bytes, which was always hardcoded to
BLCKSZ, is removed.  IO backend statistics are updated to reflect these
changes.

Bump catalog version.

Author: Nazir Bilal Yavuz
Reviewed-by: Bertrand Drouvot, Melanie Plageman
Discussion: https://postgr.es/m/CAN55FZ0oqxBaaHAEsj=xFqkzE3n5P=3RA1V_igXwL-RV7QRzyw@mail.gmail.com

doc/src/sgml/monitoring.sgml

@@ -2692,8 +2692,18 @@ description | Waiting for a newly initialized WAL file to reach durable storage
         <structfield>reads</structfield> <type>bigint</type>
        </para>
        <para>
-        Number of read operations, each of the size specified in
-        <varname>op_bytes</varname>.
+        Number of read operations.
+       </para>
+      </entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry">
+       <para role="column_definition">
+        <structfield>read_bytes</structfield> <type>numeric</type>
+       </para>
+       <para>
+        The total size of read operations in bytes.
        </para>
       </entry>
      </row>
@@ -2716,8 +2726,18 @@ description | Waiting for a newly initialized WAL file to reach durable storage
         <structfield>writes</structfield> <type>bigint</type>
        </para>
        <para>
-        Number of write operations, each of the size specified in
-        <varname>op_bytes</varname>.
+        Number of write operations.
+       </para>
+      </entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry">
+       <para role="column_definition">
+        <structfield>write_bytes</structfield> <type>numeric</type>
+       </para>
+       <para>
+        The total size of write operations in bytes.
        </para>
       </entry>
      </row>
@@ -2740,8 +2760,8 @@ description | Waiting for a newly initialized WAL file to reach durable storage
         <structfield>writebacks</structfield> <type>bigint</type>
        </para>
        <para>
-        Number of units of size <varname>op_bytes</varname> which the process
-        requested the kernel write out to permanent storage.
+        Number of units of size <symbol>BLCKSZ</symbol> (typically 8kB) which
+        the process requested the kernel write out to permanent storage.
        </para>
       </entry>
      </row>
@@ -2766,8 +2786,7 @@ description | Waiting for a newly initialized WAL file to reach durable storage
         <structfield>extends</structfield> <type>bigint</type>
        </para>
        <para>
-        Number of relation extend operations, each of the size specified in
-        <varname>op_bytes</varname>.
+        Number of relation extend operations.
        </para>
       </entry>
      </row>
@@ -2775,11 +2794,10 @@ description | Waiting for a newly initialized WAL file to reach durable storage
      <row>
       <entry role="catalog_table_entry">
        <para role="column_definition">
-        <structfield>extend_time</structfield> <type>double precision</type>
+        <structfield>extend_bytes</structfield> <type>numeric</type>
        </para>
        <para>
-        Time spent in extend operations in milliseconds (if
-        <xref linkend="guc-track-io-timing"/> is enabled, otherwise zero)
+        The total size of relation extend operations in bytes.
        </para>
       </entry>
      </row>
@@ -2787,16 +2805,11 @@ description | Waiting for a newly initialized WAL file to reach durable storage
      <row>
       <entry role="catalog_table_entry">
        <para role="column_definition">
-        <structfield>op_bytes</structfield> <type>bigint</type>
-       </para>
-       <para>
-        The number of bytes per unit of I/O read, written, or extended.
+        <structfield>extend_time</structfield> <type>double precision</type>
        </para>
        <para>
-        Relation data reads, writes, and extends are done in
-        <varname>block_size</varname> units, derived from the build-time
-        parameter <symbol>BLCKSZ</symbol>, which is <literal>8192</literal> by
-        default.
+        Time spent in extend operations in milliseconds (if
+        <xref linkend="guc-track-io-timing"/> is enabled, otherwise zero)
        </para>
       </entry>
      </row>

src/backend/catalog/system_views.sql

@@ -1156,14 +1156,16 @@ SELECT
        b.object,
        b.context,
        b.reads,
+       b.read_bytes,
        b.read_time,
        b.writes,
+       b.write_bytes,
        b.write_time,
        b.writebacks,
        b.writeback_time,
        b.extends,
+       b.extend_bytes,
        b.extend_time,
-       b.op_bytes,
        b.hits,
        b.evictions,
        b.reuses,

src/backend/storage/buffer/bufmgr.c

@@ -1165,7 +1165,7 @@ PinBufferForBlock(Relation rel,
 	}
 	if (*foundPtr)
 	{
-		pgstat_count_io_op(io_object, io_context, IOOP_HIT, 1);
+		pgstat_count_io_op(io_object, io_context, IOOP_HIT, 1, 0);
 		if (VacuumCostActive)
 			VacuumCostBalance += VacuumCostPageHit;
 
@@ -1515,7 +1515,7 @@ WaitReadBuffers(ReadBuffersOperation *operation)
 		io_start = pgstat_prepare_io_time(track_io_timing);
 		smgrreadv(operation->smgr, forknum, io_first_block, io_pages, io_buffers_len);
 		pgstat_count_io_op_time(io_object, io_context, IOOP_READ, io_start,
-								io_buffers_len);
+								1, io_buffers_len * BLCKSZ);
 
 		/* Verify each block we read, and terminate the I/O. */
 		for (int j = 0; j < io_buffers_len; ++j)
@@ -2073,7 +2073,7 @@ again:
 		 * pinners or erroring out.
 		 */
 		pgstat_count_io_op(IOOBJECT_RELATION, io_context,
-						   from_ring ? IOOP_REUSE : IOOP_EVICT, 1);
+						   from_ring ? IOOP_REUSE : IOOP_EVICT, 1, 0);
 	}
 
 	/*
@@ -2429,7 +2429,7 @@ ExtendBufferedRelShared(BufferManagerRelation bmr,
 		UnlockRelationForExtension(bmr.rel, ExclusiveLock);
 
 	pgstat_count_io_op_time(IOOBJECT_RELATION, io_context, IOOP_EXTEND,
-							io_start, extend_by);
+							io_start, 1, extend_by * BLCKSZ);
 
 	/* Set BM_VALID, terminate IO, and wake up any waiters */
 	for (uint32 i = 0; i < extend_by; i++)
@@ -3891,7 +3891,7 @@ FlushBuffer(BufferDesc *buf, SMgrRelation reln, IOObject io_object,
 	 * of a dirty shared buffer (IOCONTEXT_NORMAL IOOP_WRITE).
 	 */
 	pgstat_count_io_op_time(IOOBJECT_RELATION, io_context,
-							IOOP_WRITE, io_start, 1);
+							IOOP_WRITE, io_start, 1, BLCKSZ);
 
 	pgBufferUsage.shared_blks_written++;
 
@@ -4530,7 +4530,7 @@ FlushRelationBuffers(Relation rel)
 
 				pgstat_count_io_op_time(IOOBJECT_TEMP_RELATION,
 										IOCONTEXT_NORMAL, IOOP_WRITE,
-										io_start, 1);
+										io_start, 1, BLCKSZ);
 
 				buf_state &= ~(BM_DIRTY | BM_JUST_DIRTIED);
 				pg_atomic_unlocked_write_u32(&bufHdr->state, buf_state);
@@ -6037,7 +6037,7 @@ IssuePendingWritebacks(WritebackContext *wb_context, IOContext io_context)
 	 * blocks of permanent relations.
 	 */
 	pgstat_count_io_op_time(IOOBJECT_RELATION, io_context,
-							IOOP_WRITEBACK, io_start, wb_context->nr_pending);
+							IOOP_WRITEBACK, io_start, wb_context->nr_pending, 0);
 
 	wb_context->nr_pending = 0;
 }

src/backend/storage/buffer/localbuf.c

@@ -255,7 +255,7 @@ GetLocalVictimBuffer(void)
 
 		/* Temporary table I/O does not use Buffer Access Strategies */
 		pgstat_count_io_op_time(IOOBJECT_TEMP_RELATION, IOCONTEXT_NORMAL,
-								IOOP_WRITE, io_start, 1);
+								IOOP_WRITE, io_start, 1, BLCKSZ);
 
 		/* Mark not-dirty now in case we error out below */
 		buf_state &= ~BM_DIRTY;
@@ -279,7 +279,8 @@ GetLocalVictimBuffer(void)
 		ClearBufferTag(&bufHdr->tag);
 		buf_state &= ~(BUF_FLAG_MASK | BUF_USAGECOUNT_MASK);
 		pg_atomic_unlocked_write_u32(&bufHdr->state, buf_state);
-		pgstat_count_io_op(IOOBJECT_TEMP_RELATION, IOCONTEXT_NORMAL, IOOP_EVICT, 1);
+
+		pgstat_count_io_op(IOOBJECT_TEMP_RELATION, IOCONTEXT_NORMAL, IOOP_EVICT, 1, 0);
 	}
 
 	return BufferDescriptorGetBuffer(bufHdr);
@@ -419,7 +420,7 @@ ExtendBufferedRelLocal(BufferManagerRelation bmr,
 	smgrzeroextend(bmr.smgr, fork, first_block, extend_by, false);
 
 	pgstat_count_io_op_time(IOOBJECT_TEMP_RELATION, IOCONTEXT_NORMAL, IOOP_EXTEND,
-							io_start, extend_by);
+							io_start, 1, extend_by * BLCKSZ);
 
 	for (uint32 i = 0; i < extend_by; i++)
 	{

src/backend/storage/smgr/md.c

@@ -1401,7 +1401,7 @@ register_dirty_segment(SMgrRelation reln, ForkNumber forknum, MdfdVec *seg)
 		 * backend fsyncs.
 		 */
 		pgstat_count_io_op_time(IOOBJECT_RELATION, IOCONTEXT_NORMAL,
-								IOOP_FSYNC, io_start, 1);
+								IOOP_FSYNC, io_start, 1, 0);
 	}
 }
 
@@ -1796,7 +1796,7 @@ mdsyncfiletag(const FileTag *ftag, char *path)
 		FileClose(file);
 
 	pgstat_count_io_op_time(IOOBJECT_RELATION, IOCONTEXT_NORMAL,
-							IOOP_FSYNC, io_start, 1);
+							IOOP_FSYNC, io_start, 1, 0);
 
 	errno = save_errno;
 	return result;

src/backend/utils/activity/pgstat_backend.c

@@ -65,6 +65,8 @@ pgstat_flush_backend_entry_io(PgStat_EntryRef *entry_ref)
 
 				bktype_shstats->counts[io_object][io_context][io_op] +=
 					pending_io->counts[io_object][io_context][io_op];
+				bktype_shstats->bytes[io_object][io_context][io_op] +=
+					pending_io->bytes[io_object][io_context][io_op];
 
 				time = pending_io->pending_times[io_object][io_context][io_op];
 

src/backend/utils/activity/pgstat_io.c

@@ -23,6 +23,13 @@
 static PgStat_PendingIO PendingIOStats;
 static bool have_iostats = false;
 
+/*
+ * Check if an IOOp is tracked in bytes.  This relies on the ordering of IOOp
+ * defined in pgstat.h, so make sure to update this check when changing its
+ * elements.
+ */
+#define pgstat_is_ioop_tracked_in_bytes(io_op) \
+	((io_op) < IOOP_NUM_TYPES && (io_op) >= IOOP_EXTEND)
 
 /*
  * Check that stats have not been counted for any combination of IOObject,
@@ -66,11 +73,13 @@ pgstat_bktype_io_stats_valid(PgStat_BktypeIO *backend_io,
 }
 
 void
-pgstat_count_io_op(IOObject io_object, IOContext io_context, IOOp io_op, uint32 cnt)
+pgstat_count_io_op(IOObject io_object, IOContext io_context, IOOp io_op,
+				   uint32 cnt, uint64 bytes)
 {
 	Assert((unsigned int) io_object < IOOBJECT_NUM_TYPES);
 	Assert((unsigned int) io_context < IOCONTEXT_NUM_TYPES);
 	Assert((unsigned int) io_op < IOOP_NUM_TYPES);
+	Assert(pgstat_is_ioop_tracked_in_bytes(io_op) || bytes == 0);
 	Assert(pgstat_tracks_io_op(MyBackendType, io_object, io_context, io_op));
 
 	if (pgstat_tracks_backend_bktype(MyBackendType))
@@ -79,9 +88,11 @@ pgstat_count_io_op(IOObject io_object, IOContext io_context, IOOp io_op, uint32
 
 		entry_ref = pgstat_prep_backend_pending(MyProcNumber);
 		entry_ref->pending_io.counts[io_object][io_context][io_op] += cnt;
+		entry_ref->pending_io.bytes[io_object][io_context][io_op] += bytes;
 	}
 
 	PendingIOStats.counts[io_object][io_context][io_op] += cnt;
+	PendingIOStats.bytes[io_object][io_context][io_op] += bytes;
 
 	have_iostats = true;
 }
@@ -114,7 +125,7 @@ pgstat_prepare_io_time(bool track_io_guc)
  */
 void
 pgstat_count_io_op_time(IOObject io_object, IOContext io_context, IOOp io_op,
-						instr_time start_time, uint32 cnt)
+						instr_time start_time, uint32 cnt, uint64 bytes)
 {
 	if (track_io_timing)
 	{
@@ -153,7 +164,7 @@ pgstat_count_io_op_time(IOObject io_object, IOContext io_context, IOOp io_op,
 		}
 	}
 
-	pgstat_count_io_op(io_object, io_context, io_op, cnt);
+	pgstat_count_io_op(io_object, io_context, io_op, cnt, bytes);
 }
 
 PgStat_IO *
@@ -219,6 +230,9 @@ pgstat_io_flush_cb(bool nowait)
 				bktype_shstats->counts[io_object][io_context][io_op] +=
 					PendingIOStats.counts[io_object][io_context][io_op];
 
+				bktype_shstats->bytes[io_object][io_context][io_op] +=
+					PendingIOStats.bytes[io_object][io_context][io_op];
+
 				time = PendingIOStats.pending_times[io_object][io_context][io_op];
 
 				bktype_shstats->times[io_object][io_context][io_op] +=

src/backend/utils/adt/pgstatfuncs.c

@@ -1285,14 +1285,16 @@ typedef enum io_stat_col
 	IO_COL_OBJECT,
 	IO_COL_CONTEXT,
 	IO_COL_READS,
+	IO_COL_READ_BYTES,
 	IO_COL_READ_TIME,
 	IO_COL_WRITES,
+	IO_COL_WRITE_BYTES,
 	IO_COL_WRITE_TIME,
 	IO_COL_WRITEBACKS,
 	IO_COL_WRITEBACK_TIME,
 	IO_COL_EXTENDS,
+	IO_COL_EXTEND_BYTES,
 	IO_COL_EXTEND_TIME,
-	IO_COL_CONVERSION,
 	IO_COL_HITS,
 	IO_COL_EVICTIONS,
 	IO_COL_REUSES,
@@ -1333,11 +1335,36 @@ pgstat_get_io_op_index(IOOp io_op)
 	pg_unreachable();
 }
 
+/*
+ * Get the number of the column containing IO bytes for the specified IOOp.
+ * If an IOOp is not tracked in bytes, IO_COL_INVALID is returned.
+ */
+static io_stat_col
+pgstat_get_io_byte_index(IOOp io_op)
+{
+	switch (io_op)
+	{
+		case IOOP_EXTEND:
+			return IO_COL_EXTEND_BYTES;
+		case IOOP_READ:
+			return IO_COL_READ_BYTES;
+		case IOOP_WRITE:
+			return IO_COL_WRITE_BYTES;
+		case IOOP_EVICT:
+		case IOOP_FSYNC:
+		case IOOP_HIT:
+		case IOOP_REUSE:
+		case IOOP_WRITEBACK:
+			return IO_COL_INVALID;
+	}
+
+	elog(ERROR, "unrecognized IOOp value: %d", io_op);
+	pg_unreachable();
+}
+
 /*
  * Get the number of the column containing IO times for the specified IOOp.
- * This function encodes our assumption that IO time for an IOOp is displayed
- * in the view in the column directly after the IOOp counts. If an op has no
- * associated time, IO_COL_INVALID is returned.
+ * If an op has no associated time, IO_COL_INVALID is returned.
  */
 static io_stat_col
 pgstat_get_io_time_index(IOOp io_op)
@@ -1345,11 +1372,15 @@ pgstat_get_io_time_index(IOOp io_op)
 	switch (io_op)
 	{
 		case IOOP_READ:
+			return IO_COL_READ_TIME;
 		case IOOP_WRITE:
+			return IO_COL_WRITE_TIME;
 		case IOOP_WRITEBACK:
+			return IO_COL_WRITEBACK_TIME;
 		case IOOP_EXTEND:
+			return IO_COL_EXTEND_TIME;
 		case IOOP_FSYNC:
-			return pgstat_get_io_op_index(io_op) + 1;
+			return IO_COL_FSYNC_TIME;
 		case IOOP_EVICT:
 		case IOOP_HIT:
 		case IOOP_REUSE:
@@ -1408,18 +1439,11 @@ pg_stat_io_build_tuples(ReturnSetInfo *rsinfo,
 			else
 				nulls[IO_COL_RESET_TIME] = true;
 
-			/*
-			 * Hard-code this to the value of BLCKSZ for now. Future values
-			 * could include XLOG_BLCKSZ, once WAL IO is tracked, and constant
-			 * multipliers, once non-block-oriented IO (e.g. temporary file
-			 * IO) is tracked.
-			 */
-			values[IO_COL_CONVERSION] = Int64GetDatum(BLCKSZ);
-
 			for (int io_op = 0; io_op < IOOP_NUM_TYPES; io_op++)
 			{
 				int			op_idx = pgstat_get_io_op_index(io_op);
 				int			time_idx = pgstat_get_io_time_index(io_op);
+				int			byte_idx = pgstat_get_io_byte_index(io_op);
 
 				/*
 				 * Some combinations of BackendType and IOOp, of IOContext and
@@ -1436,19 +1460,39 @@ pg_stat_io_build_tuples(ReturnSetInfo *rsinfo,
 				else
 					nulls[op_idx] = true;
 
-				/* not every operation is timed */
-				if (time_idx == IO_COL_INVALID)
-					continue;
-
 				if (!nulls[op_idx])
 				{
-					PgStat_Counter time =
-						bktype_stats->times[io_obj][io_context][io_op];
+					/* not every operation is timed */
+					if (time_idx != IO_COL_INVALID)
+					{
+						PgStat_Counter time =
+							bktype_stats->times[io_obj][io_context][io_op];
+
+						values[time_idx] = Float8GetDatum(pg_stat_us_to_ms(time));
+					}
 
-					values[time_idx] = Float8GetDatum(pg_stat_us_to_ms(time));
+					/* not every IO is tracked in bytes */
+					if (byte_idx != IO_COL_INVALID)
+					{
+						char		buf[256];
+						PgStat_Counter byte =
+							bktype_stats->bytes[io_obj][io_context][io_op];
+
+						/* Convert to numeric */
+						snprintf(buf, sizeof buf, UINT64_FORMAT, byte);
+						values[byte_idx] = DirectFunctionCall3(numeric_in,
+															   CStringGetDatum(buf),
+															   ObjectIdGetDatum(0),
+															   Int32GetDatum(-1));
+					}
 				}
 				else
-					nulls[time_idx] = true;
+				{
+					if (time_idx != IO_COL_INVALID)
+						nulls[time_idx] = true;
+					if (byte_idx != IO_COL_INVALID)
+						nulls[byte_idx] = true;
+				}
 			}
 
 			tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc,

src/include/catalog/catversion.h

@@ -57,6 +57,6 @@
  */
 
 /*							yyyymmddN */
-#define CATALOG_VERSION_NO	202501101
+#define CATALOG_VERSION_NO	202501401
 
 #endif

src/include/catalog/pg_proc.dat

@@ -5908,18 +5908,18 @@
   proname => 'pg_stat_get_io', prorows => '30', proretset => 't',
   provolatile => 'v', proparallel => 'r', prorettype => 'record',
   proargtypes => '',
-  proallargtypes => '{text,text,text,int8,float8,int8,float8,int8,float8,int8,float8,int8,int8,int8,int8,int8,float8,timestamptz}',
-  proargmodes => '{o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o}',
-  proargnames => '{backend_type,object,context,reads,read_time,writes,write_time,writebacks,writeback_time,extends,extend_time,op_bytes,hits,evictions,reuses,fsyncs,fsync_time,stats_reset}',
+  proallargtypes => '{text,text,text,int8,numeric,float8,int8,numeric,float8,int8,float8,int8,numeric,float8,int8,int8,int8,int8,float8,timestamptz}',
+  proargmodes => '{o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o}',
+  proargnames => '{backend_type,object,context,reads,read_bytes,read_time,writes,write_bytes,write_time,writebacks,writeback_time,extends,extend_bytes,extend_time,hits,evictions,reuses,fsyncs,fsync_time,stats_reset}',
   prosrc => 'pg_stat_get_io' },
 
 { oid => '8806', descr => 'statistics: backend IO statistics',
   proname => 'pg_stat_get_backend_io', prorows => '5', proretset => 't',
   provolatile => 'v', proparallel => 'r', prorettype => 'record',
   proargtypes => 'int4',
-  proallargtypes => '{int4,text,text,text,int8,float8,int8,float8,int8,float8,int8,float8,int8,int8,int8,int8,int8,float8,timestamptz}',
-  proargmodes => '{i,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o}',
-  proargnames => '{backend_pid,backend_type,object,context,reads,read_time,writes,write_time,writebacks,writeback_time,extends,extend_time,op_bytes,hits,evictions,reuses,fsyncs,fsync_time,stats_reset}',
+  proallargtypes => '{int4,text,text,text,int8,numeric,float8,int8,numeric,float8,int8,float8,int8,numeric,float8,int8,int8,int8,int8,float8,timestamptz}',
+  proargmodes => '{i,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o}',
+  proargnames => '{backend_pid,backend_type,object,context,reads,read_bytes,read_time,writes,write_bytes,write_time,writebacks,writeback_time,extends,extend_bytes,extend_time,hits,evictions,reuses,fsyncs,fsync_time,stats_reset}',
   prosrc => 'pg_stat_get_backend_io' },
 
 { oid => '1136', descr => 'statistics: information about WAL activity',

src/include/pgstat.h

@@ -343,28 +343,42 @@ typedef enum IOContext
 
 #define IOCONTEXT_NUM_TYPES (IOCONTEXT_VACUUM + 1)
 
+/*
+ * Enumeration of IO operations.
+ *
+ * This enum categorizes IO operations into two groups, depending on if
+ * byte operations are supported.
+ *
+ * Ensure IOOP_EXTEND is the first and IOOP_WRITE is the last ones in the
+ * tracked in bytes group and that the groups stay in that order.
+ */
 typedef enum IOOp
 {
+	/* IOs not tracked in bytes */
 	IOOP_EVICT,
-	IOOP_EXTEND,
 	IOOP_FSYNC,
 	IOOP_HIT,
-	IOOP_READ,
 	IOOP_REUSE,
-	IOOP_WRITE,
 	IOOP_WRITEBACK,
+
+	/* IOs tracked in bytes */
+	IOOP_EXTEND,
+	IOOP_READ,
+	IOOP_WRITE,
 } IOOp;
 
-#define IOOP_NUM_TYPES (IOOP_WRITEBACK + 1)
+#define IOOP_NUM_TYPES (IOOP_WRITE + 1)
 
 typedef struct PgStat_BktypeIO
 {
+	uint64		bytes[IOOBJECT_NUM_TYPES][IOCONTEXT_NUM_TYPES][IOOP_NUM_TYPES];
 	PgStat_Counter counts[IOOBJECT_NUM_TYPES][IOCONTEXT_NUM_TYPES][IOOP_NUM_TYPES];
 	PgStat_Counter times[IOOBJECT_NUM_TYPES][IOCONTEXT_NUM_TYPES][IOOP_NUM_TYPES];
 } PgStat_BktypeIO;
 
 typedef struct PgStat_PendingIO
 {
+	uint64		bytes[IOOBJECT_NUM_TYPES][IOCONTEXT_NUM_TYPES][IOOP_NUM_TYPES];
 	PgStat_Counter counts[IOOBJECT_NUM_TYPES][IOCONTEXT_NUM_TYPES][IOOP_NUM_TYPES];
 	instr_time	pending_times[IOOBJECT_NUM_TYPES][IOCONTEXT_NUM_TYPES][IOOP_NUM_TYPES];
 } PgStat_PendingIO;
@@ -604,10 +618,11 @@ extern PgStat_CheckpointerStats *pgstat_fetch_stat_checkpointer(void);
 extern bool pgstat_bktype_io_stats_valid(PgStat_BktypeIO *backend_io,
 										 BackendType bktype);
 extern void pgstat_count_io_op(IOObject io_object, IOContext io_context,
-							   IOOp io_op, uint32 cnt);
+							   IOOp io_op, uint32 cnt, uint64 bytes);
 extern instr_time pgstat_prepare_io_time(bool track_io_guc);
 extern void pgstat_count_io_op_time(IOObject io_object, IOContext io_context,
-									IOOp io_op, instr_time start_time, uint32 cnt);
+									IOOp io_op, instr_time start_time,
+									uint32 cnt, uint64 bytes);
 
 extern PgStat_IO *pgstat_fetch_stat_io(void);
 extern const char *pgstat_get_io_context_name(IOContext io_context);

src/test/regress/expected/rules.out

@@ -1892,21 +1892,23 @@ pg_stat_io| SELECT backend_type,
     object,
     context,
     reads,
+    read_bytes,
     read_time,
     writes,
+    write_bytes,
     write_time,
     writebacks,
     writeback_time,
     extends,
+    extend_bytes,
     extend_time,
-    op_bytes,
     hits,
     evictions,
     reuses,
     fsyncs,
     fsync_time,
     stats_reset
-   FROM pg_stat_get_io() b(backend_type, object, context, reads, read_time, writes, write_time, writebacks, writeback_time, extends, extend_time, op_bytes, hits, evictions, reuses, fsyncs, fsync_time, stats_reset);
+   FROM pg_stat_get_io() b(backend_type, object, context, reads, read_bytes, read_time, writes, write_bytes, write_time, writebacks, writeback_time, extends, extend_bytes, extend_time, hits, evictions, reuses, fsyncs, fsync_time, stats_reset);
 pg_stat_progress_analyze| SELECT s.pid,
     s.datid,
     d.datname,