On 25 April 2017 at 22:07, Tom Lane <t...@sss.pgh.pa.us> wrote: > Craig Ringer <cr...@2ndquadrant.com> writes: >> On 25 Apr. 2017 13:37, "Heikki Linnakangas" <hlinn...@iki.fi> wrote: >>> For some data shared memory structures, that store no pointers, we wouldn't >>> need to insist that they are mapped to the same address in every backend, >>> though. In particular, shared_buffers. It wouldn't eliminate the problem, >>> though, only make it less likely, so we'd still need to retry when it does >>> happen. > >> Good point. Simply splitting out shared_buffers into a moveable segment >> would make a massive difference. Much less chance of losing the dice roll >> for mapping the fixed segment. > >> Should look at what else could be made cheaply relocatable too. > > I don't think it's worth spending any effort on. We need the retry > code anyway, and making it near impossible to hit that would only mean > that it's very poorly tested. The results upthread say that it isn't > going to be hit often enough to be a performance problem, so why worry?
Good point. Deal with it if it becomes an issue. That said, I didn't see if any of those tests covered really big shared_buffers. That could become an issue down the track at least. -- Craig Ringer 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
