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: 2021-09-07T17:08:43Z
Lists: pgsql-hackers

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On 9/6/21, 9:00 PM, "Michael Paquier" <michael@paquier.xyz> wrote:
> +   sprintf(buf, "%lu MB", size_mb);
> +   SetConfigOption("shared_memory_size", buf, PGC_INTERNAL, PGC_S_OVERRIDE);
> One small-ish comment about 0002: there is no need to add the unit
> into the buffer set as GUC_UNIT_MB would take care of that.  The patch
> looks fine.

I fixed this in v7.

> +#ifndef WIN32
> +#include <sys/mman.h>
> +#endif
> So, this is needed in ipci.c to check for MAP_HUGETLB.  I am not much
> a fan of moving around platform-specific checks when these have
> remained local to each shmem implementation.  Could it be cleaner to
> add GetHugePageSize() to win32_shmem.c and make it always declared in
> the SysV implementation?

I don't know if it's really all that much cleaner, but I did it this
way in v7.  IMO it's a little weird that GetHugePageSize() doesn't
return the value from GetLargePageMinimum(), but that's what we'd need
to do to avoid setting huge_pages_required for Windows without any
platform-specific checks.

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.