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>

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 2fadf79..5639de4 100644 (file)
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -77,6 +77,9 @@ config GENERIC_BUG
        def_bool y
        depends on BUG
 
+config GENERIC_FIND_NEXT_BIT
+       def_bool y
+
 config GENERIC_HWEIGHT
        def_bool y
 

diff --git a/arch/x86/lib/Makefile b/arch/x86/lib/Makefile
index 25df1c1..4360932 100644 (file)
--- a/arch/x86/lib/Makefile
+++ b/arch/x86/lib/Makefile
@@ -11,7 +11,7 @@ lib-y += memcpy_$(BITS).o
 ifeq ($(CONFIG_X86_32),y)
         lib-y += checksum_32.o
         lib-y += strstr_32.o
-        lib-y += bitops_32.o semaphore_32.o string_32.o
+        lib-y += semaphore_32.o string_32.o
 
         lib-$(CONFIG_X86_USE_3DNOW) += mmx_32.o
 else

diff --git a/arch/x86/lib/bitops_32.c b/arch/x86/lib/bitops_32.c
deleted file mode 100644 (file)
index b654404..0000000
--- a/arch/x86/lib/bitops_32.c
+++ /dev/null
@@ -1,70 +0,0 @@
-#include <linux/bitops.h>
-#include <linux/module.h>
-
-/**
- * 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
- */
-int find_next_bit(const unsigned long *addr, int size, int offset)
-{
-       const unsigned long *p = addr + (offset >> 5);
-       int set = 0, bit = offset & 31, res;
-
-       if (bit) {
-               /*
-                * Look for nonzero in the first 32 bits:
-                */
-               __asm__("bsfl %1,%0\n\t"
-                       "jne 1f\n\t"
-                       "movl $32, %0\n"
-                       "1:"
-                       : "=r" (set)
-                       : "r" (*p >> bit));
-               if (set < (32 - bit))
-                       return set + offset;
-               set = 32 - bit;
-               p++;
-       }
-       /*
-        * No set bit yet, search remaining full words for a bit
-        */
-       res = find_first_bit (p, size - 32 * (p - addr));
-       return (offset + set + res);
-}
-EXPORT_SYMBOL(find_next_bit);
-
-/**
- * find_next_zero_bit - find the first zero 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
- */
-int find_next_zero_bit(const unsigned long *addr, int size, int offset)
-{
-       const unsigned long *p = addr + (offset >> 5);
-       int set = 0, bit = offset & 31, res;
-
-       if (bit) {
-               /*
-                * Look for zero in the first 32 bits.
-                */
-               __asm__("bsfl %1,%0\n\t"
-                       "jne 1f\n\t"
-                       "movl $32, %0\n"
-                       "1:"
-                       : "=r" (set)
-                       : "r" (~(*p >> bit)));
-               if (set < (32 - bit))
-                       return set + offset;
-               set = 32 - bit;
-               p++;
-       }
-       /*
-        * No zero yet, search remaining full bytes for a zero
-        */
-       res = find_first_zero_bit(p, size - 32 * (p - addr));
-       return (offset + set + res);
-}
-EXPORT_SYMBOL(find_next_zero_bit);

diff --git a/arch/x86/lib/bitops_64.c b/arch/x86/lib/bitops_64.c
index 0e8f491..0eeb704 100644 (file)
--- a/arch/x86/lib/bitops_64.c
+++ b/arch/x86/lib/bitops_64.c
@@ -1,9 +1,7 @@
 #include <linux/bitops.h>
 
 #undef find_first_zero_bit
-#undef find_next_zero_bit
 #undef find_first_bit
-#undef find_next_bit
 
 static inline long
 __find_first_zero_bit(const unsigned long * addr, unsigned long size)
@@ -57,39 +55,6 @@ long find_first_zero_bit(const unsigned long * addr, unsigned long size)
        return __find_first_zero_bit (addr, size);
 }
 
-/**
- * find_next_zero_bit - find the next zero 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
- */
-long find_next_zero_bit (const unsigned long * addr, long size, long offset)
-{
-       const unsigned long * p = addr + (offset >> 6);
-       unsigned long set = 0;
-       unsigned long res, bit = offset&63;
-
-       if (bit) {
-               /*
-                * Look for zero in first word
-                */
-               asm("bsfq %1,%0\n\t"
-                   "cmoveq %2,%0"
-                   : "=r" (set)
-                   : "r" (~(*p >> bit)), "r"(64L));
-               if (set < (64 - bit))
-                       return set + offset;
-               set = 64 - bit;
-               p++;
-       }
-       /*
-        * No zero yet, search remaining full words for a zero
-        */
-       res = __find_first_zero_bit (p, size - 64 * (p - addr));
-
-       return (offset + set + res);
-}
-
 static inline long
 __find_first_bit(const unsigned long * addr, unsigned long size)
 {
@@ -136,40 +101,7 @@ long find_first_bit(const unsigned long * addr, unsigned long size)
        return __find_first_bit(addr,size);
 }
 
-/**
- * find_next_bit - find the first 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
- */
-long find_next_bit(const unsigned long * addr, long size, long offset)
-{
-       const unsigned long * p = addr + (offset >> 6);
-       unsigned long set = 0, bit = offset & 63, res;
-
-       if (bit) {
-               /*
-                * Look for nonzero in the first 64 bits:
-                */
-               asm("bsfq %1,%0\n\t"
-                   "cmoveq %2,%0\n\t"
-                   : "=r" (set)
-                   : "r" (*p >> bit), "r" (64L));
-               if (set < (64 - bit))
-                       return set + offset;
-               set = 64 - bit;
-               p++;
-       }
-       /*
-        * No set bit yet, search remaining full words for a bit
-        */
-       res = __find_first_bit (p, size - 64 * (p - addr));
-       return (offset + set + res);
-}
-
 #include <linux/module.h>
 
-EXPORT_SYMBOL(find_next_bit);
 EXPORT_SYMBOL(find_first_bit);
 EXPORT_SYMBOL(find_first_zero_bit);
-EXPORT_SYMBOL(find_next_zero_bit);

diff --git a/include/asm-x86/bitops.h b/include/asm-x86/bitops.h
index 1ae7b27..31e408d 100644 (file)
--- a/include/asm-x86/bitops.h
+++ b/include/asm-x86/bitops.h
@@ -306,6 +306,12 @@ static int test_bit(int nr, const volatile unsigned long *addr);
 #undef BIT_ADDR
 #undef ADDR
 
+unsigned long find_next_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);
+
+
 #ifdef CONFIG_X86_32
 # include "bitops_32.h"
 #else

diff --git a/include/asm-x86/bitops_32.h b/include/asm-x86/bitops_32.h
index 2513a81..7c9ed75 100644 (file)
--- a/include/asm-x86/bitops_32.h
+++ b/include/asm-x86/bitops_32.h
@@ -40,14 +40,6 @@ static inline int find_first_zero_bit(const unsigned long *addr, unsigned size)
 }
 
 /**
- * find_next_zero_bit - find the first zero bit in a memory region
- * @addr: The address to base the search on
- * @offset: The bit number to start searching at
- * @size: The maximum size to search
- */
-int find_next_zero_bit(const unsigned long *addr, int size, int offset);
-
-/**
  * __ffs - find first bit in word.
  * @word: The word to search
  *
@@ -83,14 +75,6 @@ static inline unsigned find_first_bit(const unsigned long *addr, unsigned size)
 }
 
 /**
- * find_next_bit - find the first set bit in a memory region
- * @addr: The address to base the search on
- * @offset: The bit number to start searching at
- * @size: The maximum size to search
- */
-int find_next_bit(const unsigned long *addr, int size, int offset);
-
-/**
  * ffz - find first zero in word.
  * @word: The word to search
  *

diff --git a/include/asm-x86/bitops_64.h b/include/asm-x86/bitops_64.h
index 365f820..65b20fb 100644 (file)
--- a/include/asm-x86/bitops_64.h
+++ b/include/asm-x86/bitops_64.h
@@ -6,9 +6,7 @@
  */
 
 extern long find_first_zero_bit(const unsigned long *addr, unsigned long size);
-extern long find_next_zero_bit(const unsigned long *addr, long size, long offset);
 extern long find_first_bit(const unsigned long *addr, unsigned long size);
-extern long find_next_bit(const unsigned long *addr, long size, long offset);
 
 /* return index of first bet set in val or max when no bit is set */
 static inline long __scanbit(unsigned long val, unsigned long max)

diff --git a/lib/find_next_bit.c b/lib/find_next_bit.c
index 78ccd73..5820e07 100644 (file)
--- a/lib/find_next_bit.c
+++ b/lib/find_next_bit.c
@@ -15,6 +15,8 @@
 #include <asm/byteorder.h>
 
 #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