From: Imseih (AWS), Sami <simseih@amazon.com>
To: Nathan Bossart <nathandbossart@gmail.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Justin Pryzby <pryzby@telsasoft.com>
Cc: pgsql-hackers@postgresql.org <pgsql-hackers@postgresql.org>
Subject: Re: problems with "Shared Memory and Semaphores" section of docs
Date: Fri, 17 May 2024 18:30:08 +0000
Message-ID: <B22D8E61-490D-4B89-9C62-41C36098011F@amazon.com> (raw)
In-Reply-To: <20240517174837.GB1918496@nathanxps13>
References: <20240517164452.GA1914161@nathanxps13>
<2463906.1715965795@sss.pgh.pa.us>
<20240517174837.GB1918496@nathanxps13>
>>> If the exact values
>>> are important, maybe we could introduce more GUCs like
>>> shared_memory_size_in_huge_pages that can be consulted (instead of
>>> requiring users to break out their calculators).
>>
>> I don't especially like shared_memory_size_in_huge_pages, and I don't
>> want to introduce more of those. GUCs are not the right way to expose
>> values that you can't actually set. (Yeah, I'm guilty of some of the
>> existing ones like that, but it's still not a good thing.) Maybe it's
>> time to introduce a system view for such things? It could be really
>> simple, with name and value, or we could try to steal some additional
>> ideas such as units from pg_settings.
I always found some of the preset GUCs [1] to be useful for writing SQLs used by
DBAs, particularly block_size, wal_block_size, server_version and server_version_num.
> The advantage of the GUC is that its value could be seen before trying to
> actually start the server.
Only if they have a sample in postgresql.conf file, right?
A GUC like shared_memory_size_in_huge_pages will not be.
[1] https://www.postgresql.org/docs/current/runtime-config-preset.html
Regards,
Sami
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To: pgsql-hackers@postgresql.org
Cc: simseih@amazon.com, nathandbossart@gmail.com, tgl@sss.pgh.pa.us, pryzby@telsasoft.com
Subject: Re: problems with "Shared Memory and Semaphores" section of docs
In-Reply-To: <B22D8E61-490D-4B89-9C62-41C36098011F@amazon.com>
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