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 <br...@momjian.us> http://momjian.us EnterpriseDB http://enterprisedb.com + It's impossible for everything to be true. + -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
