Kevin Grittner wrote: > Avoid extra locks in GetSnapshotData if old_snapshot_threshold < 0 > > On a big NUMA machine with 1000 connections in saturation load > there was a performance regression due to spinlock contention, for > acquiring values which were never used. Just fill with dummy > values if we're not going to use them.
old_snapshot_threshold is PGC_POSTMASTER, so this is okay AFAICS, but perhaps it'd be a good idea to add a oneline comment to guc.c indicating to verify this code if there's an intention to lift that limitation -- snapshots taken before the reload would have invalid lsn/timestamp, so the current check would simply skip the check, which would be the wrong thing to do. I think it's reasonable to want to enable this feature with a simple reload, so if we ever do that it'd be good to have a pointer about that gotcha. (I'm not proposing you do that, only add the comment for a future hacker.) -- Álvaro Herrera http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Remote DBA, 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
