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: 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: 2021-09-07T04:00:08Z
Lists: pgsql-hackers 
On Mon, Sep 06, 2021 at 11:55:42PM +0000, Bossart, Nathan wrote:
> Attached is a new patch set.  The first two patches just add the new
> GUCs, and the third is an attempt at providing useful values for those
> GUCs via -C.

+   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.

+#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?
--
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.