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x86: change x86 to use generic find_next_bit
The versions with inline assembly are in fact slower on the machines I
tested them on (in userspace) (Athlon XP 2800+, p4-like Xeon 2.8GHz, AMD
Opteron 270). The i386-version needed a fix similar to 06024f21 to avoid
crashing the benchmark.
Benchmark using: gcc -fomit-frame-pointer -Os. For each bitmap size
1...512, for each possible bitmap with one bit set, for each possible
offset: find the position of the first bit starting at offset. If you
follow ;). Times include setup of the bitmap and checking of the
results.
Athlon Xeon Opteron 32/64bit
x86-specific: 0m3.692s 0m2.820s 0m3.196s / 0m2.480s
generic: 0m2.622s 0m1.662s 0m2.100s / 0m1.572s
If the bitmap size is not a multiple of BITS_PER_LONG, and no set
(cleared) bit is found, find_next_bit (find_next_zero_bit) returns a
value outside of the range [0, size]. The generic version always returns
exactly size. The generic version also uses unsigned long everywhere,
while the x86 versions use a mishmash of int, unsigned (int), long and
unsigned long.
Using the generic version does give a slightly bigger kernel, though.
defconfig: text data bss dec hex filename
x86-specific: 4738555 481232 626688 5846475 5935cb vmlinux (32 bit)
generic: 4738621 481232 626688 5846541 59360d vmlinux (32 bit)
x86-specific: 5392395 846568 724424 6963387 6a40bb vmlinux (64 bit)
generic: 5392458 846568 724424 6963450 6a40fa vmlinux (64 bit)
Signed-off-by: Alexander van Heukelum <heukelum@fastmail.fm>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Alexander van Heukelum
Ingo Molnar
parent
18e413f719
commit
6fd92b63d0
8 changed files with 12 additions and 157 deletions
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@ -77,6 +77,9 @@ config GENERIC_BUG
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def_bool y
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depends on BUG
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config GENERIC_FIND_NEXT_BIT
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def_bool y
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config GENERIC_HWEIGHT
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def_bool y
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@ -11,7 +11,7 @@ lib-y += memcpy_$(BITS).o
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ifeq ($(CONFIG_X86_32),y)
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lib-y += checksum_32.o
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lib-y += strstr_32.o
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lib-y += bitops_32.o semaphore_32.o string_32.o
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lib-y += semaphore_32.o string_32.o
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lib-$(CONFIG_X86_USE_3DNOW) += mmx_32.o
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else
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@ -1,70 +0,0 @@
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#include <linux/bitops.h>
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#include <linux/module.h>
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/**
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* find_next_bit - find the next set bit in a memory region
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* @addr: The address to base the search on
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* @offset: The bitnumber to start searching at
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* @size: The maximum size to search
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*/
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int find_next_bit(const unsigned long *addr, int size, int offset)
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{
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const unsigned long *p = addr + (offset >> 5);
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int set = 0, bit = offset & 31, res;
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if (bit) {
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/*
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* Look for nonzero in the first 32 bits:
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*/
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__asm__("bsfl %1,%0\n\t"
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"jne 1f\n\t"
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"movl $32, %0\n"
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"1:"
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: "=r" (set)
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: "r" (*p >> bit));
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if (set < (32 - bit))
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return set + offset;
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set = 32 - bit;
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p++;
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}
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/*
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* No set bit yet, search remaining full words for a bit
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*/
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res = find_first_bit (p, size - 32 * (p - addr));
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return (offset + set + res);
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}
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EXPORT_SYMBOL(find_next_bit);
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/**
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* find_next_zero_bit - find the first zero bit in a memory region
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* @addr: The address to base the search on
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* @offset: The bitnumber to start searching at
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* @size: The maximum size to search
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*/
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int find_next_zero_bit(const unsigned long *addr, int size, int offset)
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{
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const unsigned long *p = addr + (offset >> 5);
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int set = 0, bit = offset & 31, res;
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if (bit) {
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/*
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* Look for zero in the first 32 bits.
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*/
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__asm__("bsfl %1,%0\n\t"
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"jne 1f\n\t"
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"movl $32, %0\n"
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"1:"
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: "=r" (set)
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: "r" (~(*p >> bit)));
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if (set < (32 - bit))
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return set + offset;
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set = 32 - bit;
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p++;
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}
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/*
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* No zero yet, search remaining full bytes for a zero
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*/
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res = find_first_zero_bit(p, size - 32 * (p - addr));
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return (offset + set + res);
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}
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EXPORT_SYMBOL(find_next_zero_bit);
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@ -1,9 +1,7 @@
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#include <linux/bitops.h>
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#undef find_first_zero_bit
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#undef find_next_zero_bit
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#undef find_first_bit
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#undef find_next_bit
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static inline long
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__find_first_zero_bit(const unsigned long * addr, unsigned long size)
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@ -57,39 +55,6 @@ long find_first_zero_bit(const unsigned long * addr, unsigned long size)
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return __find_first_zero_bit (addr, size);
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}
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/**
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* find_next_zero_bit - find the next zero bit in a memory region
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* @addr: The address to base the search on
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* @offset: The bitnumber to start searching at
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* @size: The maximum size to search
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*/
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long find_next_zero_bit (const unsigned long * addr, long size, long offset)
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{
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const unsigned long * p = addr + (offset >> 6);
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unsigned long set = 0;
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unsigned long res, bit = offset&63;
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if (bit) {
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/*
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* Look for zero in first word
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*/
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asm("bsfq %1,%0\n\t"
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"cmoveq %2,%0"
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: "=r" (set)
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: "r" (~(*p >> bit)), "r"(64L));
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if (set < (64 - bit))
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return set + offset;
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set = 64 - bit;
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p++;
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}
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/*
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* No zero yet, search remaining full words for a zero
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*/
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res = __find_first_zero_bit (p, size - 64 * (p - addr));
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return (offset + set + res);
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}
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static inline long
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__find_first_bit(const unsigned long * addr, unsigned long size)
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{
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@ -136,40 +101,7 @@ long find_first_bit(const unsigned long * addr, unsigned long size)
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return __find_first_bit(addr,size);
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}
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/**
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* find_next_bit - find the first set bit in a memory region
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* @addr: The address to base the search on
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* @offset: The bitnumber to start searching at
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* @size: The maximum size to search
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*/
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long find_next_bit(const unsigned long * addr, long size, long offset)
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{
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const unsigned long * p = addr + (offset >> 6);
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unsigned long set = 0, bit = offset & 63, res;
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if (bit) {
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/*
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* Look for nonzero in the first 64 bits:
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*/
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asm("bsfq %1,%0\n\t"
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"cmoveq %2,%0\n\t"
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: "=r" (set)
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: "r" (*p >> bit), "r" (64L));
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if (set < (64 - bit))
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return set + offset;
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set = 64 - bit;
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p++;
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}
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/*
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* No set bit yet, search remaining full words for a bit
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*/
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res = __find_first_bit (p, size - 64 * (p - addr));
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return (offset + set + res);
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}
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#include <linux/module.h>
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EXPORT_SYMBOL(find_next_bit);
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EXPORT_SYMBOL(find_first_bit);
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EXPORT_SYMBOL(find_first_zero_bit);
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EXPORT_SYMBOL(find_next_zero_bit);
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@ -306,6 +306,12 @@ static int test_bit(int nr, const volatile unsigned long *addr);
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#undef BIT_ADDR
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#undef ADDR
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unsigned long find_next_bit(const unsigned long *addr,
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unsigned long size, unsigned long offset);
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unsigned long find_next_zero_bit(const unsigned long *addr,
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unsigned long size, unsigned long offset);
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#ifdef CONFIG_X86_32
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# include "bitops_32.h"
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#else
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@ -39,14 +39,6 @@ static inline int find_first_zero_bit(const unsigned long *addr, unsigned size)
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return res;
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}
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/**
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* find_next_zero_bit - find the first zero bit in a memory region
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* @addr: The address to base the search on
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* @offset: The bit number to start searching at
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* @size: The maximum size to search
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*/
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int find_next_zero_bit(const unsigned long *addr, int size, int offset);
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/**
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* __ffs - find first bit in word.
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* @word: The word to search
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@ -82,14 +74,6 @@ static inline unsigned find_first_bit(const unsigned long *addr, unsigned size)
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return x;
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}
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/**
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* find_next_bit - find the first set bit in a memory region
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* @addr: The address to base the search on
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* @offset: The bit number to start searching at
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* @size: The maximum size to search
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*/
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int find_next_bit(const unsigned long *addr, int size, int offset);
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/**
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* ffz - find first zero in word.
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* @word: The word to search
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@ -6,9 +6,7 @@
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*/
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extern long find_first_zero_bit(const unsigned long *addr, unsigned long size);
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extern long find_next_zero_bit(const unsigned long *addr, long size, long offset);
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extern long find_first_bit(const unsigned long *addr, unsigned long size);
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extern long find_next_bit(const unsigned long *addr, long size, long offset);
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/* return index of first bet set in val or max when no bit is set */
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static inline long __scanbit(unsigned long val, unsigned long max)
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@ -15,6 +15,8 @@
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#include <asm/byteorder.h>
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#define BITOP_WORD(nr) ((nr) / BITS_PER_LONG)
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#undef find_next_bit
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#undef find_next_zero_bit
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/**
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* find_next_bit - find the next set bit in a memory region
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