On 20 February 2017 at 17:32, Robert Haas <robertmh...@gmail.com> wrote:
>>> Have you checked whether this >>> patch makes any noticeable performance difference? >> >> No, but then we're reducing the number of calls to PgXact directly; >> there is no heuristic involved, its just a pure saving. > > Well, it's adding a branch where there wasn't one. A branch that is avoided in almost all cases, so easy to predict. > Maybe that costs > essentially nothing and the saved write to shared memory saves > something noticeable, but for all I know it's the reverse. If I had > to guess, it would be that neither the costs nor the savings from this > are in the slightest way noticeable on a macrobenchmark, and therefore > there's not much point in changing it, but that could be 100% wrong. Given Andres' earlier measurements, it seems worth testing to me. Hopefully someone can recheck. Thanks in advance. -- Simon Riggs 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
