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

From: Simon Riggs <simon(at)2ndQuadrant(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Robert Haas <robertmhaas(at)gmail(dot)com>, Josh Berkus <josh(at)agliodbs(dot)com>, Bruce Momjian <bruce(at)momjian(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: 2014-05-07 05:23:43
Message-ID: CA+U5nMKeUQGPvTHs_cxbdLbBLTejDf_+CsnD1AkeizSho6TAzA@mail.gmail.com
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On 6 May 2014 23:28, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Robert Haas <robertmhaas(at)gmail(dot)com> writes:
>> I basically think the auto-tuning we've installed for
>> effective_cache_size is stupid. Most people are going to run with
>> only a few GB of shared_buffers, so setting effective_cache_size to a
>> small multiple of that isn't going to make many more people happy than
>> just raising the value - say from the current default of 128MB to, oh,
>> 4GB - especially because in my experience queries aren't very
>> sensitive to the exact value; it just has to not be way too small. I
>> bet the number of PostgreSQL users who would be made happy by a much
>> higher hard-coded default is not too different from the number that
>> will be made happy by the (completely unprincipled) auto-tuning.
>
> There is a lot to be said for that argument, especially considering
> that we're not even really happy with the auto-tuning mechanism,
> never mind the behavior it's trying to implement.

+1

--
Simon Riggs http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services

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