cvs commit: src/sys/kern sched_ule.c
jroberson at chesapeake.net
Mon Oct 1 02:11:25 PDT 2007
On Mon, 1 Oct 2007, Bruce Evans wrote:
> 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.
Given that the overwhelming amount of feedback by qualified poeple, I
think it's fair to say that ULE gives a more responsive system under load.
>> 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.
I meant no significant difference in performance. I'm sure there are
corner case workloads in favor of one or the other.
>> 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.
There is a significant enough class of problems that benefit from the
improved interactive priorities that people notice it. I have heard
reports from a number of laptop users who can run at lower power levels
using ULE. I am trivially able to create workloads where 4bsd falls over
well before ULE. It is true that io behavior dominates in many cases but
that's really a seperate issue.
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