[rfc] bind per-cpu timeout threads to each CPU

[Alexander Motin]

On 19.02.2014 21:51, Adrian Chadd wrote:
> On 19 February 2014 11:40, Alexander Motin <mav at freebsd.org> wrote:
>> Clock interrupt threads, same as other ones are only softly bound to
>> specific CPUs by scheduler preferring to run them on CPUs where they are
>> scheduled. So far that was enough to balance load, but allowed threads to
>> migrate, if needed. Is it too flexible for some use case?
>
> I saw it migrate under enough CPU load / pressure, right smack bang in
> the middle of doing TCP processing.
>
> So if we're moving towards supporting (among others) a pcbgroup / RSS
> hash style work load distribution across CPUs to minimise
> per-connection lock contention, we really don't want the scheduler to
> decide it can schedule things on other CPUs under enough pressure.
> That'll just make things worse.

True, though it is also not obvious that putting second thread on CPU 
run queue is better then executing it right now on another core.

-- 
Alexander Motin