On Thu, Jan 13, 2011 at 23:19, Robert Haas <robertmh...@gmail.com> wrote: > On Thu, Jan 6, 2011 at 11:37 PM, Greg Smith <g...@2ndquadrant.com> wrote: >> If it defaulted to 3% of shared_buffers, min 64K & max 16MB for the auto >> setting, it would for the most part become an autotuned parameter. That >> would make it 0.75 to 1MB at the standard anemic Linux default kernel >> parameters. Maybe more than some would like, but dropping shared_buffers >> from 24MB to 23MB to keep this from being ridiculously undersized is >> probably a win. That percentage would reach 16MB by the time shared_buffers >> was increased to 533MB, which also seems about right to me. On a really bad >> setup (brief pause to flip off Apple) with only 4MB to work with total, >> you'd end up with wal_buffers between 64 and 128K, so very close to the >> status quo. >> >> Code that up, and we could probably even remove the parameter as a tunable >> altogether. Very few would see a downside relative to any sensible >> configuration under the current situation, and many people would notice >> better automagic performance with one less parameter to tweak. Given the >> recent investigations about the serious downsides of tiny wal_buffers values >> on new Linux kernels when using open_datasync, a touch more aggression about >> this setting seems particularly appropriate to consider now. That's been >> swapped out as the default, but it's still possible people will switch to >> it. > > Would anyone like to argue vigorously for or against the above proposal? > > I'll start: I think this is a good idea. I don't have a strong > opinion on whether the exact details of Greg proposes above are > precisely optimal, but I think they're in the right ballpark. > Furthermore, we already have other things that are tuned in somewhat > similar ways (e.g. the size of the fsync request queue defaults to the > number of shared buffers) so there's precedent for it. It's one less > parameter that you have to set to make things just work.
+1, I like the idea. Would it still be there to override if necessary? -- 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
