From: Chao Li <li.evan.chao@gmail.com>
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Subject: bufmgr: pass through I/O stats context in FlushUnlockedBuffer()
Message-Id: <BC97546F-5C15-42F2-AD57-CFACDB9657D0@gmail.com>
Date: Wed, 1 Apr 2026 10:15:09 +0800
Cc: Andres Freund <andres@anarazel.de>,
 Melanie Plageman <melanieplageman@gmail.com>
To: PostgreSQL-development <pgsql-hackers@postgresql.org>
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Hi,

I noticed that FlushUnlockedBuffer() accepts io_object and io_context, =
but then ignores them and hardcodes IOOBJECT_RELATIONand =
IOCONTEXT_NORMAL instead:
```
static void
FlushUnlockedBuffer(BufferDesc *buf, SMgrRelation reln,
					IOObject io_object, IOContext =
io_context)
{
	Buffer		buffer =3D BufferDescriptorGetBuffer(buf);

	BufferLockAcquire(buffer, buf, BUFFER_LOCK_SHARE_EXCLUSIVE);
	FlushBuffer(buf, reln, IOOBJECT_RELATION, IOCONTEXT_NORMAL); // =
<=3D=3D HERE
	BufferLockUnlock(buffer, buf);
}
```

Unless I am missing something, if a function accepts these parameters, =
they should generally be used.

FlushBuffer() seems to have the same issue. It takes both io_object and =
io_context:
```
static void
FlushBuffer(BufferDesc *buf, SMgrRelation reln, IOObject io_object,
         IOContext io_context)
```

but while io_context is used, io_object is ignored:
```
    pgstat_count_io_op_time(IOOBJECT_RELATION, io_context,
          IOOP_WRITE, io_start, 1, BLCKSZ);
```

For comparison, in AsyncReadBuffers(), where io_object is also available =
locally, it is passed through and used directly:
```
    pgstat_count_io_op_time(io_object, io_context, IOOP_READ,
          io_start, 1, io_buffers_len * BLCKSZ);
```

I raised the same point while reviewing patch [1], but that patch has =
not been updated yet.

This tiny patch just makes FlushUnlockedBuffer() and FlushBuffer() use =
the io_object and io_context values passed in by the caller.

[1] Discussion: =
https://postgr.es/m/377BC880-1616-4DEF-B9EF-5E297C358F7D@gmail.com

Best regards,
--
Chao Li (Evan)
HighGo Software Co., Ltd.
https://www.highgo.com/


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=46rom=20118dfb42dfce72ada4e8a1f7ce081bf5da149809=20Mon=20Sep=2017=20=
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Date:=20Wed,=201=20Apr=202026=2009:52:41=20+0800=0ASubject:=20[PATCH=20=
v1]=20bufmgr:=20pass=20through=20I/O=20stats=20context=20in=0A=20=
FlushUnlockedBuffer()=0A=0AFlushUnlockedBuffer()=20accepted=20io_object=20=
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b/src/backend/storage/buffer/bufmgr.c=0A@@=20-4583,7=20+4583,7=20@@=20=
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io_object,=0A=20=09=20*=20When=20a=20strategy=20is=20not=20in=20use,=20=
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pgBufferUsage.shared_blks_written++;=0A@@=20-4614,7=20+4614,7=20@@=20=
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Buffer=09=09buffer=20=3D=20BufferDescriptorGetBuffer(buf);=0A=20=0A=20=09=
BufferLockAcquire(buffer,=20buf,=20BUFFER_LOCK_SHARE_EXCLUSIVE);=0A-=09=
FlushBuffer(buf,=20reln,=20IOOBJECT_RELATION,=20IOCONTEXT_NORMAL);=0A+=09=
FlushBuffer(buf,=20reln,=20io_object,=20io_context);=0A=20=09=
BufferLockUnlock(buffer,=20buf);=0A=20}=0A=20=0A--=20=0A2.50.1=20(Apple=20=
Git-155)=0A=0A=

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