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From: Tom Lane <[email protected]>
To: Magnus Hagander <[email protected]>
Cc: Julien Rouhaud <[email protected]>
Cc: Don Seiler <[email protected]>
Cc: pgsql-admin <[email protected]>
Subject: Re: Estimating HugePages Requirements?
Date: Wed, 09 Jun 2021 15:15:37 -0400
Message-ID: <[email protected]> (raw)
In-Reply-To: <CABUevExXvoPvLN70CznmQfbjwxnrdXo9gXxZwGpBoUhjtFi3Ng@mail.gmail.com>
References: <CAHJZqBBLHFNs6it-fcJ6LEUXeC5t73soR3h50zUSFpg7894qfQ@mail.gmail.com>
	<CAOBaU_ZHtRhG+MvoT6=HpbMoK=JnsJHBMmxQ-XLSVoh6fFqJHQ@mail.gmail.com>
	<CABUevExXvoPvLN70CznmQfbjwxnrdXo9gXxZwGpBoUhjtFi3Ng@mail.gmail.com>

Magnus Hagander <[email protected]> writes:
> I wonder how hard it would be to for example expose that through a
> commandline switch or tool.

Just try to start the server and see if it complains.
For instance, with shared_buffers=10000000 I get

2021-06-09 15:08:56.821 EDT [1428121] FATAL:  could not map anonymous shared memory: Cannot allocate memory
2021-06-09 15:08:56.821 EDT [1428121] HINT:  This error usually means that PostgreSQL's request for a shared memory segment exceeded available memory, swap space, or huge pages. To reduce the request size (currently 83720568832 bytes), reduce PostgreSQL's shared memory usage, perhaps by reducing shared_buffers or max_connections.

Of course, if it *does* start, you can do the other thing.

Admittedly, we could make that easier somehow; but if it took
25 years for somebody to ask for this, I'm not sure it's
worth creating a feature to make it a shade easier.

			regards, tom lane





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