As I was resuscitating my buildfarm animal lousyjack, which runs tests under valgrind, I neglected to turn off force_parallel=regress in the configuration settings. The results were fairly disastrous. The runs took about 4 times as long, and some steps failed. I'm not sure if this is a known result, so I thought I'd memorialize it in case someone else runs into the same issue. When I disabled this setting the animal turned to being happy once more.
cheers andrew -- Andrew Dunstan https://www.2ndQuadrant.com PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services