Subject: Re: MultiXact\SLRU buffers configuration
To: Andrey Borodin <x4mmm@yandex-team.ru>, Gilles Darold <gilles@darold.net>
Cc: Tomas Vondra <tomas.vondra@enterprisedb.com>,
 Tomas Vondra <tomas.vondra@2ndquadrant.com>,
 Alexander Korotkov <aekorotkov@gmail.com>,
 Anastasia Lubennikova <a.lubennikova@postgrespro.ru>,
 Daniel Gustafsson <daniel@yesql.se>,
 Kyotaro Horiguchi <horikyota.ntt@gmail.com>,
 pgsql-hackers <pgsql-hackers@postgresql.org>
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 <43F3DE92-F236-4EA5-B4D6-39BEF6BD849D@yandex-team.ru>
 <20201029134933.xd4mh2cofuf6tdfz@development>
 <65C1B4BA-D16F-4939-978B-AC8F370F5A5E@yandex-team.ru>
 <9b4d17df-b811-8323-16be-3cab913216d1@enterprisedb.com>
 <A64B924A-B08E-417D-BD3D-D396D722053B@yandex-team.ru>
 <35862787-8b4d-a290-789e-6e12dc6527e8@enterprisedb.com>
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From: Gilles Darold <gilles@darold.net>
Message-ID: <18b35f55-6b35-043a-daec-2f0e610ecc6a@darold.net>
Date: Mon, 15 Mar 2021 16:41:04 +0100
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Le 12/03/2021 à 13:44, Andrey Borodin a écrit :
>
>> 11 марта 2021 г., в 20:50, Gilles Darold <gilles@darold.net> написал(а):
>>
>>
>> The patch doesn't apply anymore in master cause of error: patch failed: src/backend/utils/init/globals.c:150
>>
>>
>>
>> An other remark about this patch is that it should be mentionned in the documentation (doc/src/sgml/config.sgml) that the new configuration variables need a server restart, for example by adding "This parameter can only be set at server start." like for shared_buffers. Patch on postgresql.conf mention it.
>>
>> And some typo to be fixed:
>>
>>
>>
>> s/Tipically/Typically/
>>
>> s/asincronous/asyncronous/
>>
>> s/confugured/configured/
>>
>> s/substrnsactions/substransactions/
>>
>>
> Thanks, Gilles! Fixed.
>
> Best regards, Andrey Borodin.
>

Hi Andrey,

I found two problems in this patch, first in src/include/miscadmin.h
multixact_members_slru_buffers is declared twice:


 extern PGDLLIMPORT int max_parallel_workers;
+extern PGDLLIMPORT int multixact_offsets_slru_buffers;
+extern PGDLLIMPORT int multixact_members_slru_buffers;
+extern PGDLLIMPORT int multixact_members_slru_buffers;  <---------
+extern PGDLLIMPORT int subtrans_slru_buffers;


In file src/backend/access/transam/multixact.c the second variable
should be multixact_buffers_slru_buffers and not
multixact_offsets_slru_buffers.


@@ -1848,13 +1848,13 @@ MultiXactShmemInit(void)
        MultiXactMemberCtl->PagePrecedes = MultiXactMemberPagePrecedes;

        SimpleLruInit(MultiXactOffsetCtl,
-                                 "MultiXactOffset",
NUM_MULTIXACTOFFSET_BUFFERS, 0,
+                                 "MultiXactOffset",
multixact_offsets_slru_buffers, 0,
                                  MultiXactOffsetSLRULock,
"pg_multixact/offsets",
                                  LWTRANCHE_MULTIXACTOFFSET_BUFFER,
                                  SYNC_HANDLER_MULTIXACT_OFFSET);
        SlruPagePrecedesUnitTests(MultiXactOffsetCtl,
MULTIXACT_OFFSETS_PER_PAGE);
        SimpleLruInit(MultiXactMemberCtl,
-                                 "MultiXactMember",
NUM_MULTIXACTMEMBER_BUFFERS, 0,
+                                 "MultiXactMember",
multixact_offsets_slru_buffers, 0,    <------------------
                                  MultiXactMemberSLRULock,
"pg_multixact/members",
                                  LWTRANCHE_MULTIXACTMEMBER_BUFFER,
                                  SYNC_HANDLER_MULTIXACT_MEMBER);


Please fix them so that I can end the review.


-- 
Gilles Darold
LzLabs GmbH
http://www.lzlabs.com/