cvs commit: src/sys/kern sched_ule.c

Bruce Evans brde at
Mon Oct 1 00:37:47 PDT 2007

On Sun, 30 Sep 2007, Jeff Roberson wrote:

> On Sat, 29 Sep 2007, Kevin Oberman wrote:

>> YMMV, but ULE seems to generally work better then 4BSD for interactive
>> uniprocessor systems. The preferred scheduler for uniprocessor servers
>> is less clear, but many test have shown ULE does better for those
>> systems in the majority of cases.
> I feel it's safe to say desktop behavior on UP is definitely superior.

This is unsafe to say.

> I 
> think there is no significant difference on UP between 4BSD and ULE

This may be safe to say, but is inconsistent with the above.

> except 
> perhaps in context switching microbenchmarks where ULE falls behind.

It is safe to say that interactive users cannot notice insignificant
differences.  It takes a micro-benchmark to notice possibly-significant
differences of hundreds or even thousands of nanonseconds for context

ULE may give higher priority to interactive processes, but most loss of
interactivity is caused by blocking on I/O, and there is nothing nothing
a scheduler can do to speed up slow or overloaded devices.


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