Kevin Grittner wrote: > Robert Haas <robertmh...@gmail.com> wrote: > > > I also think Bruce's idea of calling fsync() on each relation just > > *before* we start writing the pages from that relation might have > > some merit. > > What bothers me about that is that you may have a lot of the same > dirty pages in the OS cache as the PostgreSQL cache, and you've just > ensured that the OS will write those *twice*. I'm pretty sure that > the reason the aggressive background writer settings we use have not > caused any noticeable increase in OS disk writes is that many > PostgreSQL writes of the same buffer keep an OS buffer page from > becoming stale enough to get flushed until PostgreSQL writes to it > taper off. Calling fsync() right before doing "one last push" of > the data could be really pessimal for some workloads.
OK, maybe my idea needs to be adjusted and we should trigger an early fsync if non-fsync writes are coming in for blocks _other_ than the ones we already wrote for that checkpoint. -- 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
