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 --- lib/find_next_bit.c | 25 +++++++++---------------- 1 file changed, 9 insertions(+), 16 deletions(-) (limited to 'lib') diff --git a/lib/find_next_bit.c b/lib/find_next_bit.c index 5820e072b890..ce94c4c92d10 100644 --- a/lib/find_next_bit.c +++ b/lib/find_next_bit.c @@ -15,17 +15,12 @@ #include #define BITOP_WORD(nr) ((nr) / BITS_PER_LONG) -#undef find_next_bit -#undef find_next_zero_bit - -/** - * find_next_bit - find the next set bit in a memory region - * @addr: The address to base the search on - * @offset: The bitnumber to start searching at - * @size: The maximum size to search + +/* + * Find the next set bit in a memory region. */ -unsigned long find_next_bit(const unsigned long *addr, unsigned long size, - unsigned long offset) +unsigned long __find_next_bit(const unsigned long *addr, + unsigned long size, unsigned long offset) { const unsigned long *p = addr + BITOP_WORD(offset); unsigned long result = offset & ~(BITS_PER_LONG-1); @@ -62,15 +57,14 @@ found_first: found_middle: return result + __ffs(tmp); } - -EXPORT_SYMBOL(find_next_bit); +EXPORT_SYMBOL(__find_next_bit); /* * This implementation of find_{first,next}_zero_bit was stolen from * Linus' asm-alpha/bitops.h. */ -unsigned long find_next_zero_bit(const unsigned long *addr, unsigned long size, - unsigned long offset) +unsigned long __find_next_zero_bit(const unsigned long *addr, + unsigned long size, unsigned long offset) { const unsigned long *p = addr + BITOP_WORD(offset); unsigned long result = offset & ~(BITS_PER_LONG-1); @@ -107,8 +101,7 @@ found_first: found_middle: return result + ffz(tmp); } - -EXPORT_SYMBOL(find_next_zero_bit); +EXPORT_SYMBOL(__find_next_zero_bit); #ifdef __BIG_ENDIAN -- cgit v1.2.1