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

[John Baldwin]

On Friday, May 09, 2014 3:50:28 pm Peter Grehan wrote:
> > How about i instead do the comprimise:
> >
> > * i'll pin all other swi's
> > * default swi isn't pinned by default, but one can flip on a sysctl at
> > boot time to pin it
> >
> > How's that sound?
> 
>   And also please a sysctl that disables any swi pinning.
> 
>   It is sometimes useful to change the default cpuset, for instance to 
> allocate a subset of CPUs to some particular applications and not 
> FreeBSD. Having kernel threads pinned prevents this from happening since 
> they are in the default set.
> 
>   (Note that some network drivers are also culprits here, though 
> disabling MSI-x in them is a workaround).

I'd actually like a way to exempt certain kernel threads that are inherently
per-CPU (such as queues for NIC drivers or per-CPU swi threads) from the
default cpuset so that they don't break 'cpuset -l 0 -s 1'.  Providing some
sort of way to disable the pinning for now should be good, but I think I'd
eventually prefer the former suggestion.

-- 
John Baldwin