On 13 December 2012 22:37, Andres Freund <and...@2ndquadrant.com> wrote: > On 2012-12-13 17:29:06 -0500, Robert Haas wrote: >> On Thu, Dec 13, 2012 at 3:03 PM, Andres Freund <and...@2ndquadrant.com> >> wrote: >> > It moves a computation of the sort of: >> > >> > result -= vacuum_defer_cleanup_age; >> > if (!TransactionIdIsNormal(result)) >> > result = FirstNormalTransactionId; >> > >> > inside ProcArrayLock. But I can't really imagine that to be relevant... >> >> I can. Go look at some of the 9.2 optimizations around >> GetSnapshotData(). Those made a BIG difference under heavy >> concurrency and they were definitely micro-optimization. For example, >> the introduction of NormalTransactionIdPrecedes() was shockingly >> effective. > > But GetOldestXmin() should be called less frequently than > GetSnapshotData() by several orders of magnitudes. I don't really see > it being used in any really hot code paths?
Maybe, but that calculation doesn't *need* to be inside the lock, that is just a consequence of the current coding. -- 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
