On Mon, Dec 14, 2015 at 7:22 PM, Peter Geoghegan <pg@heroku.com> wrote:
> Thanks for taking the time to benchmark the patch!
Also, I should point out that you didn't add work_mem past the point
where the master branch will get slower, while the patch continues to
get faster. This seems to happen fairly reliably, certainly if
work_mem is sized at about 1GB, and often at lower settings. With the
POWER7 "Hydra" server, external sorting for a CREATE INDEX operation
could put any possible maintenance_work_mem setting to good use -- my
test case got faster with a 15GB maintenance_work_mem setting (the
server has 64GB of ram). I think I tried 25GB as a
maintenance_work_mem setting next, but started to get OOM errors at
that point.
Again, I point this out because I want to account for why my numbers
were better (for the benefit of other people -- I think you get this,
and are being fair).
--
Peter Geoghegan