Re: Estimating HugePages Requirements?

From: Michael Paquier <michael(at)paquier(dot)xyz>
To: "Bossart, Nathan" <bossartn(at)amazon(dot)com>
Cc: Kyotaro Horiguchi <horikyota(dot)ntt(at)gmail(dot)com>, "tgl(at)sss(dot)pgh(dot)pa(dot)us" <tgl(at)sss(dot)pgh(dot)pa(dot)us>, "robertmhaas(at)gmail(dot)com" <robertmhaas(at)gmail(dot)com>, "masao(dot)fujii(at)oss(dot)nttdata(dot)com" <masao(dot)fujii(at)oss(dot)nttdata(dot)com>, "pryzby(at)telsasoft(dot)com" <pryzby(at)telsasoft(dot)com>, "andres(at)anarazel(dot)de" <andres(at)anarazel(dot)de>, "magnus(at)hagander(dot)net" <magnus(at)hagander(dot)net>, "mark(dot)dilger(at)enterprisedb(dot)com" <mark(dot)dilger(at)enterprisedb(dot)com>, "don(at)seiler(dot)us" <don(at)seiler(dot)us>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Estimating HugePages Requirements?
Date: 2021-09-15 03:05:21
Message-ID: YUFi8ekig9VRVCb8@paquier.xyz
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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

Attachment Content-Type Size
v10-0001-Provide-useful-values-for-postgres-C-with-runtim.patch text/plain 9.1 KB

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