| From: | Jeff Janes <jeff(dot)janes(at)gmail(dot)com> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | Simon Riggs <simon(at)2ndquadrant(dot)com>, 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: | 2014-05-06 19:41:29 |
| Message-ID: | CAMkU=1x0FStYSCEke5tu95qtjwvf7k_K53TAR90B3gb3LMNcZA@mail.gmail.com |
| Views: | Raw Message | Whole Thread | Download mbox | Resend email |
| Thread: | |
| Lists: | pgsql-hackers |
On Tue, May 6, 2014 at 7:18 AM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Simon Riggs <simon(at)2ndQuadrant(dot)com> writes:
> > Lets fix e_c_s at 25% of shared_buffers and remove the parameter
> > completely, just as we do with so many other performance parameters.
>
> Apparently, you don't even understand what this parameter is for.
> Setting it smaller than shared_buffers is insane.
>
The e_c_s is assumed to be usable for each backend trying to run queries
sensitive to it. If you have dozens of such queries running simultaneously
(not something I personally witness, but also not insane) and each of these
queries has its own peculiar working set, then having e_c_s smaller than
s_b makes sense.
I have a hard time believe that this is at all common, however. Certainly
not common enough so to justify cranking the setting all the way the other
direction and then removing the crank handle.
Cheers,
Jeff
| From | Date | Subject | |
|---|---|---|---|
| Next Message | Tom Lane | 2014-05-06 19:44:35 | Re: pg_shmem_allocations view |
| Previous Message | Bruce Momjian | 2014-05-06 19:40:52 | Re: [COMMITTERS] pgsql: pgindent run for 9.4 |