SCHED_ULE should not be the default

[George Mitchell]

On 12/12/11 11:18, Bruce Cran wrote:
> On 12/12/2011 15:51, Steve Kargl wrote:
>> This comes up every 9 months or so, and must be approaching FAQ
>> status. In a HPC environment, I recommend 4BSD. Depending on the
>> workload, ULE can cause a severe increase in turn around time when
>> doing already long computations. If you have an MPI application,
>> simply launching greater than ncpu+1 jobs can show the problem. PS:
>> search the list archives for "kargl and ULE".
>
> This isn't something that can be fixed by tuning ULE? For example for
> desktop applications kern.sched.preempt_thresh should be set to 224 from
> its default. I'm wondering if the installer should ask people what the
> typical use will be, and tune the scheduler appropriately.
>

I tried my "make buildkernel" test with "dnetc" running after setting
kern.sched.preempt_thresh set to 224.  It did far worse than before,
getting only as far as compiling bxe overnight (compared to getting
to netgragh with the default kern.sched.preempt_thresh setting).
-- George Mitchell