| From: | Simon Riggs <simon(at)2ndQuadrant(dot)com> |
|---|---|
| To: | Robert Haas <robertmhaas(at)gmail(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>, 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: | 2014-05-06 22:15:17 |
| Message-ID: | CA+U5nMLt4FA_cQ61Wa1X6dNix+zJZTfoNRYUzABq6jVG5_6QWw@mail.gmail.com |
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| Lists: | pgsql-hackers |
On 6 May 2014 22:54, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
> On Tue, May 6, 2014 at 4:38 PM, Simon Riggs <simon(at)2ndquadrant(dot)com> wrote:
>> I read the code, think what to say and then say what I think, not
>> rely on dogma.
>>
>> I tried to help years ago by changing the docs on e_c_s, but that's
>> been mostly ignored down the years, as it is again here.
>
> Well, for what it's worth, I've encountered systems where setting
> effective_cache_size too low resulted in bad query plans, but I've
> never encountered the reverse situation.
I agree with that.
Though that misses my point, which is that you can't know that all of
that memory is truly available on a server with many concurrent users.
Choosing settings that undercost memory intensive plans are not the
best choice for a default strategy in a mixed workload when cache may
be better used elsewhere, even if such settings make sense for some
individual users.
--
Simon Riggs http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
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