On Fri, Sep 29, 2017 at 09:38:53PM +1000, Nicholas Piggin wrote:

Not really. There is some ability to hold onto a line for a time, but
there is no way to starve them, let alone starve hundreds of other
CPUs. They will request the cacheline exclusive and eventually get it.

OK, hardware fairness there is nice.

I would really prefer to go this way on powerpc first. We could add the
the registration APIs as basically no-ops, but which would allow the
locking approach to be changed if we find it causes issues. I'll try to
find some time and a big system when I can.

Fair enough I suppose.

quoted

A semi related issue; I suppose we can do a arch upcall to flush_tlb_mm
and reset the mm_cpumask when we change cpuset groups.

For powerpc we have been looking at how mm_cpumask can be improved.
It has real drawbacks even when you don't consider this new syscall.

What else do you use mm_cpumask for?