Re: Fix CheckpointStartLock starvation

Heikki Linnakangas <heikki(at)enterprisedb(dot)com> writes:
> On a busy system, checkpoint could be starved while queuing for the
> CheckpointStartLock. To avoid that, get rid of CheckpointStartLock and
> instead set a flag in PGPROC struct when a commit starts. After
> computing the REDO ptr, checkpoint waits for all backends that had that
> flag set to finish their commits. This eliminates the same race
> condition the CheckpointStartLock was there for, without the risk of
> starvation.

Applied with some revisions --- I did not see the point of forcing
checkpoint to wait till the transaction was fully out of its commit;
we only need it to wait till clog is updated. The procarray code
seemed overly complicated too.

regards, tom lane