Hi,
On Fri, Feb 13, 2026 at 04:13:39PM -0500, Andres Freund wrote:
> Hi,
>
> On 2026-02-13 10:24:52 +0000, Bertrand Drouvot wrote:
> >
> > That's fine by me. We could still add the others in the future if we feel the
> > need. Done that way in the attached.
>
> I'm not sure that it's unproblematic to add multiple pgstat count calls to
> every lock acquisition, particularly if it's a fastpath acquisition or a
> virtualxid lock. Notably these are external function calls, not just
> increments of a counter in an inline function.
Yeah, we could create inline functions instead.
> I also don't really know what one would do with some of the information?
>
> What does the number of virtualxid lock acquisitions tell you that the numbers
> of transactions doesn't already tell you in a more understandable way?
I agree not that much, except being able to compute a transactions/virtualxid
ratio or such. Also the idea was to report the same as pg_locks so that one
could start sampling pg_locks if he needs more details.
> What does it tell you that the deadlock checker ran N times? It notably
> doesn't count deadlocks, it counts how often we checked for deadlocks.
>
> The percentage of fastpath locks also seems not really informative, because
> that could be because we ran out of space for fastpath locks, or because a
> lock mode that's ineligible for fastpath locks was used.
Right, maybe we could add an "exceed fastpath slots" or such counter?
> What I would actually count is the amount of time waiting for locks, that
> seems vastly more useful than the number of acquisitions. We already do a
> GetCurrentTimestamp() inside the timer activations for deadlock timeout, we
> probably can figure out a way to reuse that to reduce the increase in overhead
> due to timing. We could also just count the wait time after the deadlock
> check has run.
Yeah, providing the wait_time would be great. Just to be sure, are you suggesting
to remove all the fields (i.e requests, timeouts, deadlock_timeouts and fastpath)
and just add a wait_time field instead? I think that keeping requests would make
sense to be able to get the average wait time per request.
Regards,
--
Bertrand Drouvot
PostgreSQL Contributors Team
RDS Open Source Databases
Amazon Web Services: https://aws.amazon.com
