Re: proposal: Set effective_cache_size to greater of .conf value, shared_buffers

From: Bruce Momjian <bruce(at)momjian(dot)us>
To: Amit Langote <amitlangote09(at)gmail(dot)com>
Cc: Simon Riggs <simon(at)2ndquadrant(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, Josh Berkus <josh(at)agliodbs(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Magnus Hagander <magnus(at)hagander(dot)net>, Andrew Dunstan <andrew(at)dunslane(dot)net>, Claudio Freire <klaussfreire(at)gmail(dot)com>, Merlin Moncure <mmoncure(at)gmail(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: proposal: Set effective_cache_size to greater of .conf value, shared_buffers
Date: 2014-05-15 14:24:25
Message-ID: 20140515142425.GB25053@momjian.us
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On Thu, May 15, 2014 at 10:23:19PM +0900, Amit Langote wrote:
> On Thu, May 15, 2014 at 9:06 PM, Bruce Momjian <bruce(at)momjian(dot)us> wrote:
> >
> > This is the same problem we had with auto-tuning work_mem, in that we
> > didn't know what other concurrent activity was happening. Seems we need
> > concurrent activity detection before auto-tuning work_mem and
> > effective_cache_size.
> >
>
> Perhaps I am missing something obvious here, but would mmgr have any
> useful numbers on this? Like any book-keeping info maintained by
> mcxt.c/aset.c? Would extending that interface help?

No, all memory allocat is per-process, except for shared memory. We
probably need a way to record our large local memory allocations in
PGPROC that other backends can see; same for effective cache size
assumptions we make.

--
Bruce Momjian <bruce(at)momjian(dot)us> http://momjian.us
EnterpriseDB http://enterprisedb.com

+ Everyone has their own god. +

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