RELENG_6: Which scheduler for SMP?

Kris Kennaway kris at
Wed Dec 28 20:20:39 PST 2005

Mike Jakubik wrote:

> Mark Ovens wrote:
>> I've never had any success with the ULE scheduler on my dual Athlon 
>> box running RELENG_5; it was so unstable it made Windows 3.1 look 
>> stable. In fact my current build, cvsup'd a couple of days ago, won't 
>> even boot with ULE.
>> From what I remember, ULE was intended to become the default 
>> scheduler during the life of 5.0 but that hasn't happened.
>> I've just cvsup'd the source for RELENG_6 and I'm surprised to find 
>> in the GENERIC config file:
>> #options    SCHED_ULE    # ULE scheduler
>> options     SCHED_4BSD    # 4BSD scheduler
>> so it seems 4BSD is still the default scheduler. Is ULE _still_ 
>> considered to be in development/experimental? Even the SMP config 
>> file doesn't use ULE.
> There have been substantial improvements made to it since 5. However 
> no one will be able to tell you if its 100% ready, you will just have 
> to try it on your system.
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ULE is about 10-20% slower than 4BSD except under minimal load, in my 


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