On Mon, 2017-07-24 at 21:25 +1000, Nicholas Piggin wrote:
> > +#ifdef CONFIG_PPC_BOOK3S_64
> > +static inline void inc_mm_active_cpus(struct mm_struct *mm)
> > +{
> > + atomic_inc(&mm->context.active_cpus);
> > +}
> > +#else
> > +static inline void inc_mm_active_cpus(struct mm_struct *mm) { }
> > +#endif
>
> This is a bit awkward. Can we just move the entire function to test
> cpumask and set / increment into helper functions and define them
> together with mm_is_thread_local, so it's all in one place?
I thought about it but then we have 2 variants, unless I start moving
the active_cpus into mm_context_t on all the 32-bit subarchs too, etc..
It gets messy either way.
> The extra atomic does not need to be defined when it's not used either.
>
> Also does it make sense to define it based on NR_CPUS > BITS_PER_LONG?
> If it's <= then it should be similar load and compare, no?
Right, we could.
> Looks like a good optimisation though.
Thx. It's a pre-req for further optimizations such as flushing the PID
when a single threaded process moves, so we don't have to constantly
scan the mask.
Cheers,
Ben.
