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

The patch contains a small typo in config.sgml. Probably just drop the
"is" from "is can".

+ results if this database cluster is can utilize most of the memory

Kevin.

On 8 October 2013 10:13, Bruce Momjian <bruce(at)momjian(dot)us> wrote:

> On Thu, Sep 5, 2013 at 05:14:37PM -0400, Bruce Momjian wrote:
> > On Thu, Sep 5, 2013 at 06:14:33PM +0200, Magnus Hagander wrote:
> > > > 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.
> >
> > That "auto-tuning" text came from the wal_buffer documentation, which
> > does exactly this based on shared_buffers:
> >
> > The contents of the WAL buffers are written out to disk at every
> > transaction commit, so extremely large values are unlikely to
> > provide a significant benefit. However, setting this value to at
> > least a few megabytes can improve write performance on a busy
> > --> server where many clients are committing at once. The
> auto-tuning
> >
> -----------
> > selected by the default setting of -1 should give reasonable
> > results in most cases.
> >
> > I am fine with rewording and not using -1, but we should change the
> > wal_buffer default and documentation too then. I am not sure what other
> > value than -1 to use? 0? I figure if we ever get better auto-tuning,
> > we would just remove this functionality and make it better.
>
> Patch applied with a default of 4x shared buffers. I have added a 9.4
> TODO that we might want to revisit this.
>
> --
> Bruce Momjian <bruce(at)momjian(dot)us> http://momjian.us
> EnterpriseDB http://enterprisedb.com
>
> + It's impossible for everything to be true. +
>
>
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