Tom Lane wrote: > Bruce Momjian <br...@momjian.us> writes: > > My trivial idea was: let's assume we checkpoint every 10 minutes, and > > it takes 5 minutes for us to write the data to the kernel. If no one > > else is writing to those files, we can safely wait maybe 5 more minutes > > before issuing the fsync. If, however, hundreds of writes are coming in > > for the same files in those final 5 minutes, we should fsync right away. > > Huh? I would surely hope we could assume that nobody but Postgres is > writing the database files? Or are you considering that the bgwriter > doesn't know exactly what the backends are doing? That's true, but > I still maintain that we should design the bgwriter's behavior on the > assumption that writes from backends are negligible. Certainly the > backends aren't issuing fsyncs.
Right, no one else is writing but us. When I said "no one else" I meant no other bgwrites writes are going to the files we wrote as part of the checkpoint, but have not fsync'ed yet. I assume we have two write streams --- the checkpoint writes, which we know at the start of the checkpoint, and the bgwriter writes that are happening in an unpredictable way based on database activity. -- 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
