LinuxLists.cc - [PATCH] all: remove GENERIC_FIND_FIRST

2021-05-10 23:35:27

Subject: [PATCH] all: remove GENERIC_FIND_FIRST_BIT

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/[email protected]/

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 <[email protected]>
---
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

2021-05-11 13:55:41

by Alexander Lobakin

[permalink] [raw]

Subject: Re: [PATCH] all: remove GENERIC_FIND_FIRST_BIT

From: Yury Norov <[email protected]>
Date: Mon, 10 May 2021 16:34:21 -0700

> 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/[email protected]/
>
> 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 <[email protected]>
> ---
> arch/arc/Kconfig | 1 -
> arch/arm64/Kconfig | 1 -
> arch/mips/Kconfig | 1 -

MIPS bit:

Reviewed-by: Alexander Lobakin <[email protected]>
Tested-by: Alexander Lobakin <[email protected]>

> 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(-)

Thanks,
Al

2021-05-27 00:10:05

by Will Deacon

[permalink] [raw]

Subject: Re: [PATCH] all: remove GENERIC_FIND_FIRST_BIT

2021-06-07 15:43:32

by Andy Shevchenko

[permalink] [raw]

Subject: Re: [PATCH] all: remove GENERIC_FIND_FIRST_BIT

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/[email protected]/
>
> 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:/.

> 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 <[email protected]>

> Signed-off-by: Yury Norov <[email protected]>
> ---
> 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

2021-06-09 18:15:53

by Yury Norov

[permalink] [raw]

Subject: Re: [PATCH] all: remove GENERIC_FIND_FIRST_BIT

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/[email protected]/
> >
> > 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 <[email protected]>
>
> > Signed-off-by: Yury Norov <[email protected]>
> > ---
> > 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
>