trace_lwlocks — PostgreSQL configuration parameter

If on, emit information about lightweight lock usage.

At a glance

What it does

If on, emit information about lightweight lock usage. Lightweight locks are intended primarily to provide mutual exclusion of access to shared-memory data structures.

This parameter is only available if the LOCK_DEBUG macro was defined when PostgreSQL was compiled.

(Description quoted from the official PostgreSQL documentation.)

How to apply a change

Can be set per session with SET, per role/database with ALTER ROLE/DATABASE ... SET, or globally in postgresql.conf.

Inspect the current value and source with SHOW trace_lwlocks; or SELECT name, setting, unit, context, source FROM pg_settings WHERE name = 'trace_lwlocks';.

Tuning guidance

This is a developer and debugging aid, not a performance knob. Leave it at the default in production; enable it only temporarily, on a non-production or carefully controlled system, while diagnosing a specific problem. Several options in this group add overhead, generate large volumes of log output, or can damage data if misused — turn them off again as soon as the investigation is done.

Reference

PostgreSQL documentation — trace_lwlocks.