Horton

Re: Estimating HugePages Requirements?

Michael Paquier <michael@paquier.xyz>

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From: Michael Paquier <michael@paquier.xyz>
To: "Bossart, Nathan" <bossartn@amazon.com>
Cc: Kyotaro Horiguchi <horikyota.ntt@gmail.com>, "tgl@sss.pgh.pa.us" <tgl@sss.pgh.pa.us>, "robertmhaas@gmail.com" <robertmhaas@gmail.com>, "masao.fujii@oss.nttdata.com" <masao.fujii@oss.nttdata.com>, "pryzby@telsasoft.com" <pryzby@telsasoft.com>, "andres@anarazel.de" <andres@anarazel.de>, "magnus@hagander.net" <magnus@hagander.net>, "mark.dilger@enterprisedb.com" <mark.dilger@enterprisedb.com>, "don@seiler.us" <don@seiler.us>, "pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>
Date: 2021-09-15T03:05:21Z
Lists: pgsql-hackers

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On Tue, Sep 14, 2021 at 06:00:44PM +0000, Bossart, Nathan wrote:
> I think I see more support for shared_memory_size_in_huge_pages than
> for huge_pages_needed_for_shared_memory at the moment.  I'll update
> the patch set in the next day or two to use
> shared_memory_size_in_huge_pages unless something changes in the
> meantime.

I have been looking at the patch to add the new GUC flag and the new
sequence for postgres -C, and we could have some TAP tests.  There
were two places that made sense to me: pg_checksums/t/002_actions.pl
and recovery/t/017_shm.pl.  I have chosen the former as it has
coverage across more platforms, and used data_checksums for this
purpose, with an extra positive test to check for the case where a GUC
can be queried while the server is running.

There are four parameters that are updated here:
- shared_memory_size
- wal_segment_size
- data_checksums
- data_directory_mode
That looks sensible, after looking at the full set of GUCs.

Attached is a refreshed patch (commit message is the same as v9 for
now), with some minor tweaks and the tests.

Thoughts?
--
Michael

Commits

  1. Silence extra logging when using "postgres -C" on runtime-computed GUCs

  2. doc: Improve postgres command for shared_memory_size_in_huge_pages

  3. Introduce GUC shared_memory_size_in_huge_pages

  4. Support "postgres -C" with runtime-computed GUCs

  5. Make shared_memory_size a preset option

  6. Introduce GUC shared_memory_size

  7. Move the shared memory size calculation to its own function

  8. Add new GUC, max_worker_processes, limiting number of bgworkers.