Re: Estimating HugePages Requirements? - Mailing list pgsql-hackers

From Michael Paquier
Subject Re: Estimating HugePages Requirements?
Date
Msg-id YS8jgN37QvlrKnzQ@paquier.xyz
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In response to Re: Estimating HugePages Requirements?  ("Bossart, Nathan" <bossartn@amazon.com>)
Responses Re: Estimating HugePages Requirements?  ("Bossart, Nathan" <bossartn@amazon.com>)
Re: Estimating HugePages Requirements?  (Andres Freund <andres@anarazel.de>)
List pgsql-hackers
On Tue, Aug 31, 2021 at 05:37:52AM +0000, Bossart, Nathan wrote:
> I moved the GUC calculation to ipci.c, adjusted the docs, and added a
> huge_pages_required GUC.  It's still a little rough around the edges,
> and I haven't tested it on Windows, but this seems like the direction
> the patch is headed.

Hmm.  I am not sure about the addition of huge_pages_required, knowing
that we would have shared_memory_size.  I'd rather let the calculation
part to the user with a scan of /proc/meminfo.

+#elif defined(WIN32)
+   hp_size = GetLargePageMinimum();
+#endif
+
+#if defined(MAP_HUGETLB) || defined(WIN32)
+   hp_required = (size_b / hp_size) + 1;
As of [1], there is the following description:
"If the processor does not support large pages, the return value is
zero."
So there is a problem here.

[1]: https://docs.microsoft.com/en-us/windows/win32/api/memoryapi/nf-memoryapi-getlargepageminimum
--
Michael

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