Periodic rant about SCHED_ULE

From: George Mitchell <>
Date: Tue, 21 Mar 2023 22:52:16 UTC
Yes, you've all heard it before, but I've just reverified on FreeBSD
13.1-RELEASE-p7 that SCHED_ULE gives terrible performance for "make
buildworld" in the presence of a totally compute-bound job (misc/dnetc
from ports) running at nice 20.  World builds in:
15597 seconds with SCHED_4BSD without dnetc
20477 seconds with SCHED_4BSD with dnetc
16006 seconds with SCHED_ULE without dnetc
50290 seconds with SCHED_ULE with dnetc.
When I ask why SCHED_ULE is the default scheduler, I have been told more
than once that there is some circumstance in which it gives superior
performance.  But no one seems to know what circumstance that is.  Guess
what!  I propose that SCHED_4BSD be the default scheduler.     -- George