Re: Multiple Xids in PGPROC?

Alvaro Herrera <alvherre@dcc.uchile.cl> writes:
> I think if we want to do nontrivial manipulations in PGPROC we should
> make sure it's properly locked.  Maybe it's a good time to implement the
> locking suggested here?  With a LWLock instead of a spinlock, of course;
> we would need MaxBackends extra LWLocks.

Given the performance issues we're currently seeing with spinlocks
on SMP machines, I'm not sure I want to turn GetSnapshot from a
get-one-lock operation into a get-one-lock-per-backend operation :-(
The comment you were looking at was written on the assumption that
grabbing a spinlock is cheap, but it seems it isn't ...
        regards, tom lane