v1-0001-WIP-Show-WAL-write-and-fsync-stats-on-pg_stat_io.patch

From eb557114161e865807e39a53a24d03f5f0abe4f5 Mon Sep 17 00:00:00 2001
From: Nazir Bilal Yavuz <byavuz81@gmail.com>
Date: Wed, 28 Jun 2023 12:34:28 +0300
Subject: [PATCH v1] WIP: Show WAL write and fsync stats on pg_stat_io

This patch aims to showing WAL write and fsync stats per backend on
pg_stat_io view.
---
 src/backend/access/transam/xlog.c      | 8 ++++++++
 src/backend/utils/activity/pgstat_io.c | 9 ++++++++-
 src/include/pgstat.h                   | 3 ++-
 3 files changed, 18 insertions(+), 2 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 8b0710abe6..2ee6c21398 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -2207,6 +2207,10 @@ XLogWrite(XLogwrtRqst WriteRqst, TimeLineID tli, bool flexible)
 
 					INSTR_TIME_SET_CURRENT(duration);
 					INSTR_TIME_ACCUM_DIFF(PendingWalStats.wal_write_time, duration, start);
+					pgstat_count_io_op_time(IOOBJECT_WAL, IOCONTEXT_NORMAL, IOOP_WRITE, start, 1);
+				} else
+				{
+					pgstat_count_io_op_n(IOOBJECT_WAL, IOCONTEXT_NORMAL, IOOP_WRITE, 1);
 				}
 
 				PendingWalStats.wal_write++;
@@ -8233,6 +8237,10 @@ issue_xlog_fsync(int fd, XLogSegNo segno, TimeLineID tli)
 
 		INSTR_TIME_SET_CURRENT(duration);
 		INSTR_TIME_ACCUM_DIFF(PendingWalStats.wal_sync_time, duration, start);
+		pgstat_count_io_op_time(IOOBJECT_WAL, IOCONTEXT_NORMAL, IOOP_FSYNC, start, 1);
+	} else
+	{
+		pgstat_count_io_op_n(IOOBJECT_WAL, IOCONTEXT_NORMAL, IOOP_FSYNC, 1);
 	}
 
 	PendingWalStats.wal_sync++;
diff --git a/src/backend/utils/activity/pgstat_io.c b/src/backend/utils/activity/pgstat_io.c
index eb7d35d422..e5cb3c7219 100644
--- a/src/backend/utils/activity/pgstat_io.c
+++ b/src/backend/utils/activity/pgstat_io.c
@@ -231,6 +231,8 @@ pgstat_get_io_object_name(IOObject io_object)
 			return "relation";
 		case IOOBJECT_TEMP_RELATION:
 			return "temp relation";
+		case IOOBJECT_WAL:
+			return "wal";
 	}
 
 	elog(ERROR, "unrecognized IOObject value: %d", io_object);
@@ -313,9 +315,9 @@ pgstat_tracks_io_bktype(BackendType bktype)
 		case B_ARCHIVER:
 		case B_LOGGER:
 		case B_WAL_RECEIVER:
-		case B_WAL_WRITER:
 			return false;
 
+		case B_WAL_WRITER:
 		case B_AUTOVAC_LAUNCHER:
 		case B_AUTOVAC_WORKER:
 		case B_BACKEND:
@@ -350,6 +352,11 @@ pgstat_tracks_io_object(BackendType bktype, IOObject io_object,
 	if (!pgstat_tracks_io_bktype(bktype))
 		return false;
 
+
+	if (io_context != IOCONTEXT_NORMAL &&
+		io_object == IOOBJECT_WAL)
+		return false;
+
 	/*
 	 * Currently, IO on temporary relations can only occur in the
 	 * IOCONTEXT_NORMAL IOContext.
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 57a2c0866a..fb7d3abf22 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -277,9 +277,10 @@ typedef enum IOObject
 {
 	IOOBJECT_RELATION,
 	IOOBJECT_TEMP_RELATION,
+	IOOBJECT_WAL,
 } IOObject;
 
-#define IOOBJECT_NUM_TYPES (IOOBJECT_TEMP_RELATION + 1)
+#define IOOBJECT_NUM_TYPES (IOOBJECT_WAL + 1)
 
 typedef enum IOContext
 {
-- 
2.25.1