On 17 January 2013 15:14, Heikki Linnakangas <hlinnakan...@vmware.com> wrote: > On 17.01.2013 16:53, Robert Haas wrote: >> >> On Thu, Jan 17, 2013 at 3:49 AM, Pavan Deolasee >> <pavan.deola...@gmail.com> wrote: >>> >>> May be you've already addressed that concern with the proven >>> performance numbers, but I'm not sure. >> >> >> It would be nice to hear what Heikki's reasons were for adding >> PD_ALL_VISIBLE in the first place. > > > The idea was to avoid clearing the bit in the VM page on every update, when > the bit is known to not be set, ie. when the PD_ALL_VISIBLE flag is not set. > I assumed the traffic and contention on the VM page would be a killer > otherwise. I don't remember if I ever actually tested that though. Maybe I > was worrying about nothing and hitting the VM page on every update is ok.
Presumably we remember the state of the VM so we can skip the re-visit after every write? -- 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
