[PATCH 5/6] powerpc/mm: Optimize detection of thread local mm's

[Nicholas Piggin]

On Mon, 24 Jul 2017 23:46:44 +1000
Michael Ellerman <mpe at ellerman.id.au> wrote:

> Nicholas Piggin <npiggin at gmail.com> writes:
> 
> > On Mon, 24 Jul 2017 14:28:02 +1000
> > Benjamin Herrenschmidt <benh at kernel.crashing.org> wrote:
> >  
> >> Instead of comparing the whole CPU mask every time, let's
> >> keep a counter of how many bits are set in the mask. Thus
> >> testing for a local mm only requires testing if that counter
> >> is 1 and the current CPU bit is set in the mask.  
> ...
> >
> > 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?  
> 
> Do we make a machine with that few CPUs? ;)
> 
> I don't think it's worth special casing, all the distros run with much
> much larger NR_CPUs than that.

Not further special-casing, but just casing it based on NR_CPUS
rather than BOOK3S.

Thanks,
Nick