Horton

Re: Estimating HugePages Requirements?

Nathan Bossart <bossartn@amazon.com>

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From: "Bossart, Nathan" <bossartn@amazon.com>
To: Michael Paquier <michael@paquier.xyz>
Cc: Justin Pryzby <pryzby@telsasoft.com>, Andres Freund <andres@anarazel.de>, Magnus Hagander <magnus@hagander.net>, Mark Dilger <mark.dilger@enterprisedb.com>, Don Seiler <don@seiler.us>, "pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>
Date: 2021-09-02T16:46:56Z
Lists: pgsql-hackers 
On 9/2/21, 12:54 AM, "Michael Paquier" <michael@paquier.xyz> wrote:
> Thanks.  Anyway, we don't really need huge_pages_required on Windows,
> do we?  The following docs of Windows tell what do to when using large
> pages:
> https://docs.microsoft.com/en-us/windows/win32/memory/large-page-support
>
> The backend code does that as in PGSharedMemoryCreate(), now that I
> look at it.  And there is no way to change the minimum large page size
> there as far as I can see because that's decided by the processor, no?
> There is a case for shared_memory_size on Windows to be able to adjust
> the sizing of the memory of the host, though.

Yeah, huge_pages_required might not serve much purpose for Windows.
We could always set it to -1 for Windows if it seems like it'll do
more harm than good.

> At the end it would be nice to not finish with two GUCs.  Both depend
> on the reordering of the actions done by the postmaster, so I'd be
> curious to hear the thoughts of others on this particular point.

Of course.  It'd be great to hear others' thoughts on this stuff.

Nathan

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.