| From: | Peter Geoghegan <pg(at)heroku(dot)com> |
|---|---|
| To: | Simon Riggs <simon(at)2ndquadrant(dot)com> |
| Cc: | Josh Berkus <josh(at)agliodbs(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Bruce Momjian <bruce(at)momjian(dot)us>, Magnus Hagander <magnus(at)hagander(dot)net>, Andrew Dunstan <andrew(at)dunslane(dot)net>, Robert Haas <robertmhaas(at)gmail(dot)com>, 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 05:35:50 |
| Message-ID: | CAM3SWZSjUbNQrrB5fStD7vza=uEe-7TO0myonbX02z3q7NirwA@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Tue, May 6, 2014 at 10:20 PM, Simon Riggs <simon(at)2ndquadrant(dot)com> wrote:
> On 6 May 2014 23:47, Josh Berkus <josh(at)agliodbs(dot)com> wrote:
>
>> If you're going to make
>> an argument in favor of different tuning advice, then do it based on
>> something in which you actually believe, based on hard evidence.
>
> The proposed default setting of 4x shared_buffers is unprincipled
> *and* lacks hard evidence from you and everybody else.
+1. In my view, we probably should have set it to a much higher
absolute default value. The main problem with setting it to any
multiple of shared_buffers that I can see is that shared_buffers is a
very poor proxy for what effective_cache_size is supposed to
represent. In general, the folk wisdom around sizing shared_buffers
has past its sell-by date.
--
Peter Geoghegan
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