HEADS UP: ULE is the default scheduler now

Jeff Roberson jroberson at chesapeake.net
Sat Jan 24 19:12:42 PST 2004

On Sat, 24 Jan 2004, Jeff Roberson wrote:

> ULE has entered into its probationary period as the default scheduler.
> This is intended to give it wider exposure to work out the last few kinks.
> If all goes well it will remain the default through the rest of the 5.x
> series.  If you aren't running it now, please switch over.
> I have been out of town or very busy over the last few months.  I should
> be more available to address things as they come up now.  If anyone is
> aware of any current issues, please contact me with any details you may
> have.

I was asked to follow up with a summary of why you might want to use ULE.
For the average user, interactivity is reported to be better in many
cases.  This means less skipping, jerking, etc. in interactive
applications while the machine is very busy.  This will not prevent
problems due to overload disk subsystems, but it does help with overloaded

On SMP machines ULE has per cpu run queues which allow for CPU
affinity, CPU binding, advanced HyperThreading support, as well as
providing a framework for more optimizations in the future.  This means
that as our kernel is locked better the scheduler will be able to make
more efficient use of the available parallel resources.

ULE has been stable for some time.  The only problems that are likely to
remain are corner cases where interactivity is not as good or where
performance is not as good as with the old scheduler.


> Thanks,
> Jeff

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