On 2014-09-09 17:54:03 -0400, Robert Haas wrote:
> So, that's committed, then.
Yay, finally.
> I think we should pick something that uses
> spinlocks and is likely to fail spectacularly if we haven't got this
> totally right yet, and de-volatilize it. And then watch to see what
> turns red in the buildfarm and/or which users start screaming.
Good plan.
> I'm inclined to propose lwlock.c as a candidate, since that's very
> widely used and a place where we know there's significant contention.
I suggest, additionally possibly, GetSnapshotData(). It's surely one of
the hottest functions in postgres, and I've seen some performance
increases from de-volatilizing it. IIRC it requires one volatile cast in
one place to enforce that a variable is accessed only once. Not sure if
we want to add such volatile casts or use something like linux'
ACCESS_ONCE macros for some common types. Helps to grep for places
worthy of inspection.
Greetings,
Andres Freund
-- Andres Freund http://www.2ndQuadrant.com/PostgreSQL Development, 24x7 Support, Training &
Services