Messages in this thread Patch in this message | | | Date | Tue, 1 Apr 2008 11:46:19 +0200 | From | Alexander van Heukelum <> | Subject | Re: [PATCH] x86: generic versions of find_first_(zero_)bit, convert i386 |
| |
x86: generic versions of find_first_(zero_)bit, convert i386
Generic versions of __find_first_bit and __find_first_zero_bit are introduced as simplified versions of __find_next_bit and __find_next_zero_bit. Their compilation and use are guarded by a new config variable GENERIC_FIND_FIRST_BIT.
The generic versions of find_first_bit and find_first_zero_bit are implemented in terms of the newly introduced __find_first_bit and __find_first_zero_bit.
This patch does not remove the i386-specific implementation, but it does switch i386 to use the generic functions by setting GENERIC_FIND_FIRST_BIT=y for X86_32.
Signed-off-by: Alexander van Heukelum <heukelum@fastmail.fm>
arch/x86/Kconfig | 3 ++ include/asm-x86/bitops_32.h | 2 + include/linux/bitops.h | 34 +++++++++++++++++++++++++ lib/Makefile | 1 + lib/find_next_bit.c | 58 +++++++++++++++++++++++++++++++++++++++++++ 5 files changed, 98 insertions(+), 0 deletions(-)
---
> I guess we should keep the bitops.h portions alive for the moment > though (surrounded by #ifndef GENERIC_FIND_FIRST_BIT), to make it > easy for anyone to flip the Kconfig bit around via a oneliner patch > and do some benchmarking? At least initially - i'm convinced that > we want the generic versions in the long run. (especially if, as > your patches do it, the generic code picks up the easy constant > tests and optimizes them at build time) > > Ingo
Keeping the old version alive for the moment is fine with me. Here is a replacement patch that does exactly that. Runs on i386 with this patch and also with GENERIC_FIND_FIRST_BIT=n.
I'll finish the patches for X86_64 and the constant-size bitmap optimizations after work.
Greetings, Alexander
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index 6b3626d..fa7d16d 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -80,6 +80,9 @@ config GENERIC_BUG def_bool y depends on BUG +config GENERIC_FIND_FIRST_BIT + def_bool X86_32 + config GENERIC_FIND_NEXT_BIT def_bool y diff --git a/include/asm-x86/bitops_32.h b/include/asm-x86/bitops_32.h index 3ed64b2..ba2c0de 100644 --- a/include/asm-x86/bitops_32.h +++ b/include/asm-x86/bitops_32.h @@ -5,6 +5,7 @@ * Copyright 1992, Linus Torvalds. */ +#ifndef CONFIG_GENERIC_FIND_FIRST_BIT /** * find_first_zero_bit - find the first zero bit in a memory region * @addr: The address to start the search at @@ -59,6 +60,7 @@ static inline unsigned find_first_bit(const unsigned long *addr, unsigned size) } return x; } +#endif #ifdef __KERNEL__ diff --git a/include/linux/bitops.h b/include/linux/bitops.h index 3865f2c..355d67b 100644 --- a/include/linux/bitops.h +++ b/include/linux/bitops.h @@ -113,6 +113,40 @@ static inline unsigned fls_long(unsigned long l) } #ifdef __KERNEL__ +#ifdef CONFIG_GENERIC_FIND_FIRST_BIT +extern unsigned long __find_first_bit(const unsigned long *addr, + unsigned long size); + +/** + * find_first_bit - find the first set bit in a memory region + * @addr: The address to start the search at + * @size: The maximum size to search + * + * Returns the bit number of the first set bit. + */ +static __always_inline unsigned long +find_first_bit(const unsigned long *addr, unsigned long size) +{ + return __find_first_bit(addr, size); +} + +extern unsigned long __find_first_zero_bit(const unsigned long *addr, + unsigned long size); + +/** + * find_first_zero_bit - find the first cleared bit in a memory region + * @addr: The address to start the search at + * @size: The maximum size to search + * + * Returns the bit number of the first cleared bit. + */ +static __always_inline unsigned long +find_first_zero_bit(const unsigned long *addr, unsigned long size) +{ + return __find_first_zero_bit(addr, size); +} +#endif /* CONFIG_GENERIC_FIND_FIRST_BIT */ + #ifdef CONFIG_GENERIC_FIND_NEXT_BIT extern unsigned long __find_next_bit(const unsigned long *addr, unsigned long size, unsigned long offset); diff --git a/lib/Makefile b/lib/Makefile index 23de261..14c93e1 100644 --- a/lib/Makefile +++ b/lib/Makefile @@ -30,6 +30,7 @@ obj-$(CONFIG_DEBUG_SPINLOCK) += spinlock_debug.o lib-$(CONFIG_RWSEM_GENERIC_SPINLOCK) += rwsem-spinlock.o lib-$(CONFIG_RWSEM_XCHGADD_ALGORITHM) += rwsem.o lib-$(CONFIG_SEMAPHORE_SLEEPERS) += semaphore-sleepers.o +lib-$(CONFIG_GENERIC_FIND_FIRST_BIT) += find_next_bit.o lib-$(CONFIG_GENERIC_FIND_NEXT_BIT) += find_next_bit.o obj-$(CONFIG_GENERIC_HWEIGHT) += hweight.o obj-$(CONFIG_LOCK_KERNEL) += kernel_lock.o diff --git a/lib/find_next_bit.c b/lib/find_next_bit.c index ce94c4c..d3f5784 100644 --- a/lib/find_next_bit.c +++ b/lib/find_next_bit.c @@ -16,6 +16,7 @@ #define BITOP_WORD(nr) ((nr) / BITS_PER_LONG) +#ifdef CONFIG_GENERIC_FIND_NEXT_BIT /* * Find the next set bit in a memory region. */ @@ -102,6 +103,63 @@ found_middle: return result + ffz(tmp); } EXPORT_SYMBOL(__find_next_zero_bit); +#endif /* CONFIG_GENERIC_FIND_NEXT_BIT */ + +#ifdef CONFIG_GENERIC_FIND_FIRST_BIT +/* + * Find the first set bit in a memory region. + */ +unsigned long __find_first_bit(const unsigned long *addr, + unsigned long size) +{ + const unsigned long *p = addr; + unsigned long result = 0; + unsigned long tmp; + + while (size & ~(BITS_PER_LONG-1)) { + if ((tmp = *(p++))) + goto found; + result += BITS_PER_LONG; + size -= BITS_PER_LONG; + } + if (!size) + return result; + + tmp = (*p) & (~0UL >> (BITS_PER_LONG - size)); + if (tmp == 0UL) /* Are any bits set? */ + return result + size; /* Nope. */ +found: + return result + __ffs(tmp); +} +EXPORT_SYMBOL(__find_first_bit); + +/* + * Find the first cleared bit in a memory region. + */ +unsigned long __find_first_zero_bit(const unsigned long *addr, + unsigned long size) +{ + const unsigned long *p = addr; + unsigned long result = 0; + unsigned long tmp; + + while (size & ~(BITS_PER_LONG-1)) { + if (~(tmp = *(p++))) + goto found; + result += BITS_PER_LONG; + size -= BITS_PER_LONG; + } + if (!size) + return result; + + tmp = (*p) | (~0UL << size); + if (tmp == ~0UL) /* Are any bits zero? */ + return result + size; /* Nope. */ +found: + return result + ffz(tmp); +} +EXPORT_SYMBOL(__find_first_zero_bit); +#endif /* CONFIG_GENERIC_FIND_FIRST_BIT */ #ifdef __BIG_ENDIAN
| |