Re: [PATCH] all: remove GENERIC_FIND_FIRST_BIT

[Yury Norov]

On Mon, Jun 07, 2021 at 06:39:38PM +0300, Andy Shevchenko wrote:
> 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.
> 
> Subject like s/all:/arch:/.

Ok, thanks. I will resend shortly as part of series, to fix m68k
issue.
 
> > 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.
> 
> This is rather comment (should be below cutter '---' line).
> 
> Anyway, seems good to my by the code:
> Reviewed-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
> 
> > 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(-)
> > 
> > diff --git a/arch/arc/Kconfig b/arch/arc/Kconfig
> > index bc8d6aecfbbd..9c991ba50db3 100644
> > --- a/arch/arc/Kconfig
> > +++ b/arch/arc/Kconfig
> > @@ -19,7 +19,6 @@ config ARC
> >  	select COMMON_CLK
> >  	select DMA_DIRECT_REMAP
> >  	select GENERIC_ATOMIC64 if !ISA_ARCV2 || !(ARC_HAS_LL64 && ARC_HAS_LLSC)
> > -	select GENERIC_FIND_FIRST_BIT
> >  	# for now, we don't need GENERIC_IRQ_PROBE, CONFIG_GENERIC_IRQ_CHIP
> >  	select GENERIC_IRQ_SHOW
> >  	select GENERIC_PCI_IOMAP
> > diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> > index e09a9591af45..9d5b36f7d981 100644
> > --- a/arch/arm64/Kconfig
> > +++ b/arch/arm64/Kconfig
> > @@ -108,7 +108,6 @@ config ARM64
> >  	select GENERIC_CPU_AUTOPROBE
> >  	select GENERIC_CPU_VULNERABILITIES
> >  	select GENERIC_EARLY_IOREMAP
> > -	select GENERIC_FIND_FIRST_BIT
> >  	select GENERIC_IDLE_POLL_SETUP
> >  	select GENERIC_IRQ_IPI
> >  	select GENERIC_IRQ_PROBE
> > diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
> > index b72458215d20..3ddae7918386 100644
> > --- a/arch/mips/Kconfig
> > +++ b/arch/mips/Kconfig
> > @@ -27,7 +27,6 @@ config MIPS
> >  	select GENERIC_ATOMIC64 if !64BIT
> >  	select GENERIC_CMOS_UPDATE
> >  	select GENERIC_CPU_AUTOPROBE
> > -	select GENERIC_FIND_FIRST_BIT
> >  	select GENERIC_GETTIMEOFDAY
> >  	select GENERIC_IOMAP
> >  	select GENERIC_IRQ_PROBE
> > diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
> > index c1ff874e6c2e..3a10ceb8a097 100644
> > --- a/arch/s390/Kconfig
> > +++ b/arch/s390/Kconfig
> > @@ -125,7 +125,6 @@ config S390
> >  	select GENERIC_CPU_AUTOPROBE
> >  	select GENERIC_CPU_VULNERABILITIES
> >  	select GENERIC_ENTRY
> > -	select GENERIC_FIND_FIRST_BIT
> >  	select GENERIC_GETTIMEOFDAY
> >  	select GENERIC_PTDUMP
> >  	select GENERIC_SMP_IDLE_THREAD
> > diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> > index b83364a15d34..6a7d8305365e 100644
> > --- a/arch/x86/Kconfig
> > +++ b/arch/x86/Kconfig
> > @@ -123,7 +123,6 @@ config X86
> >  	select GENERIC_CPU_VULNERABILITIES
> >  	select GENERIC_EARLY_IOREMAP
> >  	select GENERIC_ENTRY
> > -	select GENERIC_FIND_FIRST_BIT
> >  	select GENERIC_IOMAP
> >  	select GENERIC_IRQ_EFFECTIVE_AFF_MASK	if SMP
> >  	select GENERIC_IRQ_MATRIX_ALLOCATOR	if X86_LOCAL_APIC
> > diff --git a/arch/x86/um/Kconfig b/arch/x86/um/Kconfig
> > index 95d26a69088b..40d6a06e41c8 100644
> > --- a/arch/x86/um/Kconfig
> > +++ b/arch/x86/um/Kconfig
> > @@ -8,7 +8,6 @@ endmenu
> >  
> >  config UML_X86
> >  	def_bool y
> > -	select GENERIC_FIND_FIRST_BIT
> >  
> >  config 64BIT
> >  	bool "64-bit kernel" if "$(SUBARCH)" = "x86"
> > diff --git a/include/asm-generic/bitops/find.h b/include/asm-generic/bitops/find.h
> > index 0d132ee2a291..8a7b70c79e15 100644
> > --- a/include/asm-generic/bitops/find.h
> > +++ b/include/asm-generic/bitops/find.h
> > @@ -95,8 +95,6 @@ unsigned long find_next_zero_bit(const unsigned long *addr, unsigned long size,
> >  }
> >  #endif
> >  
> > -#ifdef CONFIG_GENERIC_FIND_FIRST_BIT
> > -
> >  /**
> >   * find_first_bit - find the first set bit in a memory region
> >   * @addr: The address to start the search at
> > @@ -136,16 +134,6 @@ unsigned long find_first_zero_bit(const unsigned long *addr, unsigned long size)
> >  
> >  	return _find_first_zero_bit(addr, size);
> >  }
> > -#else /* CONFIG_GENERIC_FIND_FIRST_BIT */
> > -
> > -#ifndef find_first_bit
> > -#define find_first_bit(addr, size) find_next_bit((addr), (size), 0)
> > -#endif
> > -#ifndef find_first_zero_bit
> > -#define find_first_zero_bit(addr, size) find_next_zero_bit((addr), (size), 0)
> > -#endif
> > -
> > -#endif /* CONFIG_GENERIC_FIND_FIRST_BIT */
> >  
> >  #ifndef find_last_bit
> >  /**
> > diff --git a/lib/Kconfig b/lib/Kconfig
> > index a38cc61256f1..8346b3181214 100644
> > --- a/lib/Kconfig
> > +++ b/lib/Kconfig
> > @@ -59,9 +59,6 @@ config GENERIC_STRNLEN_USER
> >  config GENERIC_NET_UTILS
> >  	bool
> >  
> > -config GENERIC_FIND_FIRST_BIT
> > -	bool
> > -
> >  source "lib/math/Kconfig"
> >  
> >  config NO_GENERIC_PCI_IOPORT_MAP
> > -- 
> > 2.25.1
> > 
> 
> -- 
> With Best Regards,
> Andy Shevchenko
>