On Tue, Sep 20, 2011 at 10:03 AM, Heikki Linnakangas <heikki.linnakan...@enterprisedb.com> wrote: > On 20.09.2011 11:18, Simon Riggs wrote: >> >> The bgwriter avoids I/O, if it is operating correctly. This patch >> ensures it continues to operate even during heavy checkpoints. So it >> helps avoid extra I/O during a period of very high I/O activity. > > I don't see what difference it makes which process does the I/O. If a > write() by checkpointer process blocks, any write()s by the separate > bgwriter process at that time will block too. If the I/O is not saturated, > and the checkpoint write()s don't block, then even without this patch, the > bgwriter process can handle its usual bgwriter duties during checkpoint just > fine. (And if the I/O is not saturated, it's not an I/O bound system > anyway.)
Whatever value you assign to the bgwriter, then this patch makes sure that happens during heavy fsyncs. -- Simon Riggs http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training & Services -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
