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

Michael Ellerman mpe at ellerman.id.au
Mon Jul 24 23:46:44 AEST 2017

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.


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