HEADS UP: Scheduler change

Scott Long scottl at samsco.org
Tue Sep 7 14:01:29 PDT 2004


In the interest of getting RELENG_5 stable and ready for 5.3, we are
going to switch the scheduler in 6-CURRENT from SCHED_ULE to SCHED_4BSD.
Tests are showing that the 4BSD is a bit more stable under load than
ULE, and is a LOT morestable than ULE with PREEMPTION enabled.  This
does not mean that ULE is being removed or that we have lost confidence
in the direction and features of ULE.  By changing this we can focus on
stability for the rest of the RELENG_5 cycle.  I'd encourage anyone who
is interested in the ULE scheduler to talk to Julian Elischer and Jeff
Roberson about what needs to be done with it.  Once 5.3 is released we
can look at switching 6-CURRENT back to ULE if it makes sense.


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