Can I speed up the running of functional tests? I am running the Bitcoin Core functional tests using the test runner and it is taking a long time to get through all the tests. Is there a way to speed it up?
test/functional/test_runner.py --extended
The Bitcoin Core test README states:

By default, up to 4 tests will be run in parallel by test_runner. To
specify how many jobs to run, append --jobs=n
The individual tests and the test_runner harness have many
command-line options. Run test/functional/test_runner.py -h to see
them all.

Pieter Wuille also explained how he gets the total time down below 4 minutes on GitHub:

You can run them in parallel; if you have sufficient RAM pretty extremely even. test_runner.py -j60 works fine on my 4-core 32 GiB RAM system, taking 3m46s. A lot of the time consists of processes waiting for each other, so it's not actually CPU bound.