From 64970b68d2b3ed32b964b0b30b1b98518fde388e Mon Sep 17 00:00:00 2001 From: Alexander van Heukelum Date: Tue, 11 Mar 2008 16:17:19 +0100 Subject: x86, generic: optimize find_next_(zero_)bit for small constant-size bitmaps This moves an optimization for searching constant-sized small bitmaps form x86_64-specific to generic code. On an i386 defconfig (the x86#testing one), the size of vmlinux hardly changes with this applied. I have observed only four places where this optimization avoids a call into find_next_bit: In the functions return_unused_surplus_pages, alloc_fresh_huge_page, and adjust_pool_surplus, this patch avoids a call for a 1-bit bitmap. In __next_cpu a call is avoided for a 32-bit bitmap. That's it. On x86_64, 52 locations are optimized with a minimal increase in code size: Current #testing defconfig: 146 x bsf, 27 x find_next_*bit text data bss dec hex filename 5392637 846592 724424 6963653 6a41c5 vmlinux After removing the x86_64 specific optimization for find_next_*bit: 94 x bsf, 79 x find_next_*bit text data bss dec hex filename 5392358 846592 724424 6963374 6a40ae vmlinux After this patch (making the optimization generic): 146 x bsf, 27 x find_next_*bit text data bss dec hex filename 5392396 846592 724424 6963412 6a40d4 vmlinux [ tglx@linutronix.de: build fixes ] Signed-off-by: Ingo Molnar --- include/asm-generic/bitops/find.h | 2 ++ 1 file changed, 2 insertions(+) (limited to 'include/asm-generic') diff --git a/include/asm-generic/bitops/find.h b/include/asm-generic/bitops/find.h index 72a51e5a12ef..1914e9742512 100644 --- a/include/asm-generic/bitops/find.h +++ b/include/asm-generic/bitops/find.h @@ -1,11 +1,13 @@ #ifndef _ASM_GENERIC_BITOPS_FIND_H_ #define _ASM_GENERIC_BITOPS_FIND_H_ +#ifndef CONFIG_GENERIC_FIND_NEXT_BIT extern unsigned long find_next_bit(const unsigned long *addr, unsigned long size, unsigned long offset); extern unsigned long find_next_zero_bit(const unsigned long *addr, unsigned long size, unsigned long offset); +#endif #define find_first_bit(addr, size) find_next_bit((addr), (size), 0) #define find_first_zero_bit(addr, size) find_next_zero_bit((addr), (size), 0) -- cgit v1.2.3