On Tue, Sep 20, 2011 at 9:06 AM, Heikki Linnakangas <heikki.linnakan...@enterprisedb.com> wrote: > On 20.09.2011 10:48, Simon Riggs wrote: >> >> On Fri, Sep 16, 2011 at 2:38 AM, Fujii Masao<masao.fu...@gmail.com> >> wrote: >>> >>> On Fri, Sep 16, 2011 at 7:53 AM, Simon Riggs<si...@2ndquadrant.com> >>> wrote: >>>> >>>> This patch splits bgwriter into 2 processes: checkpointer and >>>> bgwriter, seeking to avoid contentious changes. Additional changes are >>>> expected in this release to build upon these changes for both new >>>> processes, though this patch stands on its own as both a performance >>>> vehicle and in some ways a refcatoring to simplify the code. >>> >>> I like this idea to simplify the code. How much performance gain can we >>> expect by this patch? >> >> On heavily I/O bound systems, this is likely to make a noticeable >> difference, since bgwriter reduces I/O in user processes. > > Hmm. If the system is I/O bound, it doesn't matter which process performs > the I/O. It's still the same amount of I/O in total, and in an I/O bound > system, that's what determines the overall throughput.
That's true, but not relevant. 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. -- 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