On Thu, Sep 5, 2013 at 3:01 AM, Bruce Momjian <br...@momjian.us> wrote: > On Tue, Jan 8, 2013 at 08:40:44PM -0500, Andrew Dunstan wrote: >> >> On 01/08/2013 08:08 PM, Tom Lane wrote: >> >Robert Haas <robertmh...@gmail.com> writes: >> >>On Tue, Jan 8, 2013 at 7:17 PM, Tom Lane <t...@sss.pgh.pa.us> wrote: >> >>>... And I don't especially like the idea of trying to >> >>>make it depend directly on the box's physical RAM, for the same >> >>>practical reasons Robert mentioned. >> >>For the record, I don't believe those problems would be particularly >> >>hard to solve. >> >Well, the problem of "find out the box's physical RAM" is doubtless >> >solvable if we're willing to put enough sweat and tears into it, but >> >I'm dubious that it's worth the trouble. The harder part is how to know >> >if the box is supposed to be dedicated to the database. Bear in mind >> >that the starting point of this debate was the idea that we're talking >> >about an inexperienced DBA who doesn't know about any configuration knob >> >we might provide for the purpose. >> > >> >I'd prefer to go with a default that's predictable and not totally >> >foolish --- and some multiple of shared_buffers seems like it'd fit the >> >bill. >> >> +1. That seems to be by far the biggest bang for the buck. Anything >> else will surely involve a lot more code for not much more benefit. > > I have developed the attached patch which implements an auto-tuned > effective_cache_size which is 4x the size of shared buffers. I had to > set effective_cache_size to its old 128MB default so the EXPLAIN > regression tests would pass unchanged.
That's not really autotuning though. ISTM that making the *default* 4 x shared_buffers might make perfect sense, but do we really need to hijack the value of "-1" for that? That might be useful for some time when we have actual autotuning, that somehow inspects the system and tunes it from there. I also don't think it should be called autotuning, when it's just a "smarter default value". I like the feature, though, just not the packaging. -- Magnus Hagander Me: http://www.hagander.net/ Work: http://www.redpill-linpro.com/ -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
