Re: [PATCH 0/6] lib/find_bit: fast path for small bitmaps

[Yury Norov]

On Fri, Jan 29, 2021 at 12:45 PM Yury Norov <yury.norov@xxxxxxxxx> wrote:
>
> Bitmap operations are much simpler and faster in case of small bitmaps, whicn
> fit into a single word. In linux/bitmap.h we have a machinery that allows
> compiler to replace actual function call with a few instructions if bitmaps
> passed into the function is small and its size is known at compile time.
>
> find_*_bit() API lacks this functionality; despite users will benefit from it
> a lot. One important example is cpumask subsystem, when NR_CPUS <= BITS_PER_LONG.
> In the very best case, the compiler may replace a find_*_bit() call for such a
> bitmap with a single ffs or ffz instruction.
>
> Tools is synchronized with new implementation where needed.

Sorry for the broken enumeration . If it's too confusing, please let me know
and I'll resend.