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(-) 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
