Nicholas Piggin [off-list ref] writes:

On Mon, 24 Jul 2017 14:28:02 +1000
Benjamin Herrenschmidt [off-list ref] wrote:

quoted

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.

cheers