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Re: Adding locks statistics

Bertrand Drouvot <bertranddrouvot.pg@gmail.com>

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From: Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
To: Andres Freund <andres@anarazel.de>
Cc: Michael Paquier <michael@paquier.xyz>, Jeff Davis <pgsql@j-davis.com>, Greg Sabino Mullane <htamfids@gmail.com>, pgsql-hackers@lists.postgresql.org
Date: 2026-02-20T17:26:37Z
Lists: pgsql-hackers 
Hi,

On Fri, Feb 20, 2026 at 11:02:49AM -0500, Andres Freund wrote:
> Hi,
> 
> On 2026-02-20 06:38:07 +0000, Bertrand Drouvot wrote:
> > > If the delay is very
> > > short it's probably also not that interesting to track, but I guess that's
> > > debatable.
> > 
> > v6 was introducing timed_waits so that we have:
> > 
> > waits
> > timed_waits
> > wait_time
> > fastpath_exceeded
> > 
> > timed_waits and wait_time were incremented together and waits was incremented
> > unconditionally. I like the idea of being able to track the numbers of waits
> > whatever the value of log_lock_waits (or the new track_lock_timing) is. Also
> > one could compare waits vs timed_waits.
> 
> How could a user benefit from that split? To me this is pointless number
> gathering that wastes resources and confuses users.

I was thinking that could be useful to know the distribution between "long" waits
(greater than the deadlock timeout) among all the waits.

If the vast majority are long waits that may indicate that the application is
misbehaving (as opposed to a tiny percentage of long waits).

I was also thinking to bring those stats per-backend (as a next step) and that
could also probably be more useful (distribution per host for example, thanks to
joining with pg_stat_activity).

Regards,

-- 
Bertrand Drouvot
PostgreSQL Contributors Team
RDS Open Source Databases
Amazon Web Services: https://aws.amazon.com

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Fix injection point detach timing problem in TAP test for lock stats

  2. Use single LWLock for lock statistics in pgstats

  3. Add tests for lock statistics, take two

  4. Remove isolation test lock-stats

  5. Avoid including clog.h in proc.h

  6. Don't include storage/lock.h in so many headers

  7. Add support for lock statistics in pgstats

  8. Move some code blocks in lock.c and proc.c

  9. Move declarations related to locktags from lock.h to new locktag.h