On Thu, May 14, 2009 at 1:55 PM, Tom Lane <t...@sss.pgh.pa.us> wrote: > Robert Haas <robertmh...@gmail.com> writes: >> On Thu, May 14, 2009 at 1:28 PM, Tom Lane <t...@sss.pgh.pa.us> wrote: >>> GetSnapshotData doesn't take an exclusive lock. Neither does start or >>> end of a read-only transaction. AFAIK there is no reason, and certainly >>> no shred of experimental evidence, to think that ProcArrayLock >>> contention is the bottleneck for read-only scenarios. > >> I think Simon's point was that it is O(n) rather than O(1), not that >> it took an exclusive lock. > > I think my point was that there's no evidence that GetSnapshotData > is where the scalability issue is. Without some evidence there's no > point in kluging it up.
Sure. I don't think anyone was proposing to commit something without first testing it. Supposing that the patch can be shown to improve performance for all-read-only workloads, and supposing further that the patch can be shown to have no material negative impact on write-heavy workloads, it would also be interesting to throw in a bit of scattered write traffic and see whether that completely negates the benefit or not. ...Robert -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
