Re: [PATCH] all: remove GENERIC_FIND_FIRST_BIT

[Will Deacon]

On Mon, May 10, 2021 at 04:34:21PM -0700, Yury Norov wrote:
> In the 5.12 cycle we enabled the GENERIC_FIND_FIRST_BIT config option
> for ARM64 and MIPS. It increased performance and shrunk .text size; and
> so far I didn't receive any negative feedback on the change.
> 
> https://lore.kernel.org/linux-arch/20210225135700.1381396-1-yury.norov@xxxxxxxxx/
> 
> I think it's time to make all architectures use find_{first,last}_bit()
> unconditionally and remove the corresponding config option.
> 
> This patch doesn't introduce functional changes for arc, arm64, mips,
> s390 and x86 because they already enable GENERIC_FIND_FIRST_BIT. There
> will be no changes for arm because it implements find_{first,last}_bit
> in arch code. For other architectures I expect improvement both in
> performance and .text size.
> 
> It would be great if people with an access to real hardware would share
> the output of bloat-o-meter and lib/find_bit_benchmark.
> 
> Signed-off-by: Yury Norov <yury.norov@xxxxxxxxx>
> ---
>  arch/arc/Kconfig                  |  1 -
>  arch/arm64/Kconfig                |  1 -
>  arch/mips/Kconfig                 |  1 -
>  arch/s390/Kconfig                 |  1 -
>  arch/x86/Kconfig                  |  1 -
>  arch/x86/um/Kconfig               |  1 -
>  include/asm-generic/bitops/find.h | 12 ------------
>  lib/Kconfig                       |  3 ---
>  8 files changed, 21 deletions(-)

Acked-by: Will Deacon <will@xxxxxxxxxx>

Will