Old BufferDesc refcount in PrintBufferDescs and PrintPinnedBufs

Since this patch takes out a lock to read the BufferDesc state, I also need
to release the lock, which I've added to this patch.

On Fri, Jan 17, 2025 at 2:11 PM Jacob Brazeal <jacob.brazeal@gmail.com>
wrote:

Jacob Brazeal <jacob.brazeal@gmail.com> writes:

In bufmgr.c we have the debugging functions PrintBufferDescs
and PrintPinnedBufs, which are typically hidden behind the flag
#ifdef NOT_USED. These functions reference the old buf->refcount and
buf->flags fields, and so they no longer compile. I attached a patch to
use BUF_STATE_GET_REFCOUNT instead and removed the reference to buf->flags.

Hmm. So those functions have not compiled since 48354581a of
2016-04-10, and nobody's noticed. Moreover, whatever use-case
they do have would be reduced a good deal by taking a buffer
lock (which might not be available, or our own process might
hold it already).

I'd vote for just removing them...

regards, tom lane

On Fri, Jan 17, 2025 at 9:53 PM Tom Lane <tgl@sss.pgh.pa.us> wrote:

Jacob Brazeal <jacob.brazeal@gmail.com> writes:

In bufmgr.c we have the debugging functions PrintBufferDescs
and PrintPinnedBufs, which are typically hidden behind the flag
#ifdef NOT_USED. These functions reference the old buf->refcount and
buf->flags fields, and so they no longer compile. I attached a patch to
use BUF_STATE_GET_REFCOUNT instead and removed the reference to

buf->flags.

Hmm. So those functions have not compiled since 48354581a of
2016-04-10, and nobody's noticed. Moreover, whatever use-case
they do have would be reduced a good deal by taking a buffer
lock (which might not be available, or our own process might
hold it already).

I'd vote for just removing them...

regards, tom lane

Sounds good! v3 attached.

On Fri, Jan 17, 2025 at 11:14:02PM -0800, Jacob Brazeal wrote:

Sounds good! v3 attached.

Removal sounds good to me. Any objections from anybody?

Andres, perhaps you have some experience using that and would prefer
keep them and make them work?
--
Michael

Hi,

On 2025-01-19 09:37:54 +0900, Michael Paquier wrote:

On Fri, Jan 17, 2025 at 11:14:02PM -0800, Jacob Brazeal wrote:

Sounds good! v3 attached.

Removal sounds good to me. Any objections from anybody?

Andres, perhaps you have some experience using that and would prefer
keep them and make them work?

I think they're pretty useless, tbh. There's too many buffers that just
printing them out is helpful - pg_buffercache is going to be a better
bet. When debugging issues where pg_buffercache isn't an option (e.g. because
it's a hang that doesn't allow running pg_buffercache), using
DebugPrintBufferRefcount() is much more targeted.

Greetings,

Andres Freund

Andres Freund <andres@anarazel.de> writes:

On 2025-01-19 09:37:54 +0900, Michael Paquier wrote:

Removal sounds good to me. Any objections from anybody?
Andres, perhaps you have some experience using that and would prefer
keep them and make them work?

I think they're pretty useless, tbh. There's too many buffers that just
printing them out is helpful - pg_buffercache is going to be a better
bet. When debugging issues where pg_buffercache isn't an option (e.g. because
it's a hang that doesn't allow running pg_buffercache), using
DebugPrintBufferRefcount() is much more targeted.

Sounds like we're in agreement. I'll push Jacob's second patch.

regards, tom lane