Date: Wed, 27 Nov 2024 13:50:29 +0000
To: Nazir Bilal Yavuz <byavuz81@gmail.com>
From: Matheus Alcantara <mths.dev@pm.me>
Cc: PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Subject: Re: Using read stream in autoprewarm
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Hi,

Newer reviewer here, trying to understand more about the read stream API.

On Tuesday, November 26th, 2024 at 11:07 AM, Nazir Bilal Yavuz <byavuz81@gm=
ail.com> wrote:

> Any feedback would be appreciated.

I've executed the same test of 5 databases with each of them having 1 table=
 of
3GB of size and I've got very similar results.

I've also tested using a single database with 4 tables with ~60GB of size a=
nd
the results compared with master was more closer but still an improvement. =
Note
that I've also increased the default shared_buffers to 7GB to see how it wo=
rks
with large buffer pools.
  - patched: 5.4259 s
  - master: 5.53186 s

Not to much to say about the code, I'm currently learning more about the re=
ad
stream API and Postgresql hacking itself. Just some minor points and questi=
ons
about the patches.


v2-0002-Count-free-buffers-at-the-start-of-the-autoprewar.patch
--- a/src/backend/storage/buffer/freelist.c
+/*
+ * get_number_of_free_buffers -- a lockless way to get the number of free
+ *=09=09=09=09=09=09=09=09 buffers in buffer pool.
+ *
+ * Note that result continuosly changes as free buffers are moved out by o=
ther
+ * operations.
+ */
+int
+get_number_of_free_buffers(void)

typo on continuosly -> continuously


v2-0001-Use-read-stream-in-autoprewarm.patch
+=09bool=09   *rs_have_free_buffer =3D per_buffer_data;
+
+
+=09*rs_have_free_buffer =3D true;
+

Not sure if I understand why this variable is needed, it seems that it is o=
nly
written and never read? Just as comparison, the block_range_read_stream_cb
callback used on pg_prewarm seems to not use the per_buffer_data parameter.


--
Matheus Alcantara
EDB: https://www.enterprisedb.com