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| author | Alexander van Heukelum <heukelum@mailshack.com> | 2008-03-11 16:17:19 +0100 |
|---|---|---|
| committer | Ingo Molnar <mingo@elte.hu> | 2008-04-26 19:21:16 +0200 |
| commit | 64970b68d2b3ed32b964b0b30b1b98518fde388e (patch) | |
| tree | 7d8eb5ea3ab1a841afa0f7ae1c65e7be4a9ca690 /include/asm-generic/bitops | |
| parent | 60b6783a044a55273b637983f52965c2808a6b86 (diff) | |
| download | linux-64970b68d2b3ed32b964b0b30b1b98518fde388e.tar.bz2 | |
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 <mingo@elte.hu>
Diffstat (limited to 'include/asm-generic/bitops')
| -rw-r--r-- | include/asm-generic/bitops/find.h | 2 |
1 files changed, 2 insertions, 0 deletions
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) |