SCHED_ULE should not be the default

[Tom Evans]

On Thu, Dec 15, 2011 at 12:42 AM, Jeremy Chadwick
<freebsd at jdc.parodius.com> wrote:
> On Thu, Dec 15, 2011 at 12:39:50AM +0100, O. Hartmann wrote:
>> On 12/14/11 18:54, Tom Evans wrote:
>> > I believe the correct thing to do is to put some extra documentation
>> > into the handbook about scheduler choice, noting the potential issues
>> > with loading NCPU+1 CPU bound processes. Perhaps making it easier to
>> > switch scheduler would also help?
>
> Replying to Tom's comment here:
>
> It is already easy to switch schedulers.  You change the option in your
> kernel config, rebuild kernel (world isn't necessary as long as you
> haven't csup'd between your last rebuild and now), make installkernel,
> shutdown -r now, done.

Your definition of 'easy' differs wildly from mine. How is that in any
way 'easy' to do across 200 servers?

>
> If what you're proposing is to make the scheduler changeable in
> real-time?  I think that would require a **lot** of work for something
> that very few people would benefit from (please stop for a moment and
> think about the majority of the userbase, not just niche environments; I
> say this politely, not with any condescension BTW).  Sure, it'd be
> "nice to have", but should be extremely low on the priority list (IMO).

Real time scheduler changing would be insane! I was thinking that
both/any/all schedulers could be compiled into the kernel, and the
choice of which one to use becomes a boot time configuration. You
don't have to recompile the kernel to change timecounter.

Cheers

Tom