On 2016-05-14 18:49:27 +0200, Fabien COELHO wrote: > > Hello, > > > Please find the results for the following 3 scenarios with unpatched master: > > > > 1. Default settings for *_flush_after : TPS = *10677.662356* > > 2. backend_flush_after=0, rest defaults : TPS = *18452.655936* > > 3. backend_flush_after=0, bgwriter_flush_after=0, > > wal_writer_flush_after=0, checkpoint_flush_after=0 : TPS = *18614.479962* > > Thanks for these runs.
Yes! > These raw tps suggest that {backend,bgwriter}_flush_after should better be > zero for this kind of load.Whether it should be the default is unclear yet, > because as Andres pointed out this is one kind of load. FWIW, I don't think {backend,bgwriter} are the same here. It's primarily backend that matters. This is treating the os page cache as an extension of postgres' buffer cache. That really primarily matters for backend_, because otherwise backends spend time waiting for IO. Andres -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers