1) For ease of creating a massive amount of test ad hoc tasks install this admin tool https://github.com/catalyst/moodle-tool_testtasks   2) For easy of visibility into seeing what tasks are running, install this admin tool: https://github.com/catalyst/moodle-tool_lockstats Then configure it: $CFG->lock_factory = "\\tool_lockstats\\proxy_lock_factory" ; $CFG->proxied_lock_factory = "\\core\\lock\\postgres_lock_factory" ;   3) Remove the scaling throttle: $CFG->task_adhoc_concurrency_limit = 1000 ; $CFG->task_adhoc_max_runtime = 1000 ;   3) Queue up a very large number of small ad hoc tasks, eg 1000 tasks which each take 1 second to run. /admin/tool/testtasks/cli $ php queue_adhoc_tasks.php -n=1000 -d=1   4) Now fire up a single ad hoc task processor in the background: $ php admin/tool/task/cli/adhoc_task.php --execute &   5) Note in the lock stats tool (/admin/tool/lockstats/) that there is usually 1 current task lock at any given time, reload the report a few times   6) Repeat steps 4 & 5 adding more and more background processes. Without the patch in place you will naturally hit a limit of around 3-4 concurrent processors with an actual task lock. ie with 20 processes around 16-17 will be idle doing nothing in usleep. With the patch applied you should be able to scale up linearly as much as you want.   7) Rinse and repeat with the 3 different lock implementations