sched_ule: roundrobin_callout replacement ?

John Baldwin jhb at
Thu Mar 6 13:33:57 UTC 2008

On Monday 18 February 2008 10:25:13 am Andriy Gapon wrote:
> I see that sched_4bsd has a NOP callout with a purpose of forcing a
> context switch (via softclock), so that something like a preemption
> could happen (e.g. for threads in a tight calculation loop).
> What serves the similar purpose for sched_ule?
> Or, how sched_ule deals with the issue without needing softclock's help?

It's gone in newer versions of 4BSD in HEAD actually.  ULE does it by checking 
in sched_clock() to see if the current thread has used up its quantum.  If so 

John Baldwin

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