redonkable/alistair23-linux
redonkable/alistair23-linux
1
0
Fork 0
Code Releases Activity

s390/bitops: optimize set_bit() for constant values

Browse source 
Since zEC12 we have the interlocked-access facility 2 which allows to
use the instructions ni/oi/xi to update a single byte in storage with
compare-and-swap semantics.
So change set_bit(), clear_bit() and change_bit() to generate such code
instead of a compare-and-swap loop (or using the load-and-* instruction
family), if possible.
This reduces the text segment by yet another 8KB (defconfig).

Alternatively the long displacement variants niy/oiy/xiy could have
been used, but the extended displacement field is usually not needed
and therefore would only increase the size of the text segment again.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
This commit is contained in:
Heiko Carstens 2013-09-17 09:48:44 +02:00 committed by Martin Schwidefsky
parent 370b0b5f77
commit 4ae803253e
2 changed files with 37 additions and 1 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

36
arch/s390/include/asm/bitops.h
View file

@ -151,6 +151,18 @@ static inline void set_bit(unsigned long nr, volatile unsigned long *ptr)
unsigned long *addr = __bitops_word(nr, ptr);
unsigned long mask;
#ifdef CONFIG_HAVE_MARCH_ZEC12_FEATURES
if (__builtin_constant_p(nr)) {
unsigned char *caddr = __bitops_byte(nr, ptr);
asm volatile(
"oi %0,%b1\n"
: "+Q" (*caddr)
: "i" (1 << (nr & 7))
: "cc");
return;
}
#endif
mask = 1UL << (nr & (BITS_PER_LONG - 1));
__BITOPS_LOOP(addr, mask, __BITOPS_OR);
}
@ -160,6 +172,18 @@ static inline void clear_bit(unsigned long nr, volatile unsigned long *ptr)
unsigned long *addr = __bitops_word(nr, ptr);
unsigned long mask;
#ifdef CONFIG_HAVE_MARCH_ZEC12_FEATURES
if (__builtin_constant_p(nr)) {
unsigned char *caddr = __bitops_byte(nr, ptr);
asm volatile(
"ni %0,%b1\n"
: "+Q" (*caddr)
: "i" (~(1 << (nr & 7)))
: "cc");
return;
}
#endif
mask = ~(1UL << (nr & (BITS_PER_LONG - 1)));
__BITOPS_LOOP(addr, mask, __BITOPS_AND);
}
@ -169,6 +193,18 @@ static inline void change_bit(unsigned long nr, volatile unsigned long *ptr)
unsigned long *addr = __bitops_word(nr, ptr);
unsigned long mask;
#ifdef CONFIG_HAVE_MARCH_ZEC12_FEATURES
if (__builtin_constant_p(nr)) {
unsigned char *caddr = __bitops_byte(nr, ptr);
asm volatile(
"xi %0,%b1\n"
: "+Q" (*caddr)
: "i" (1 << (nr & 7))
: "cc");
return;
}
#endif
mask = 1UL << (nr & (BITS_PER_LONG - 1));
__BITOPS_LOOP(addr, mask, __BITOPS_XOR);
}

2
arch/s390/kernel/head.S
View file

@ -437,7 +437,7 @@ ENTRY(startup_kdump)
#if defined(CONFIG_64BIT)
#if defined(CONFIG_MARCH_ZEC12)
.long 3, 0xc100efe3, 0xf46ce000, 0x00400000
.long 3, 0xc100efe3, 0xf46ce800, 0x00400000
#elif defined(CONFIG_MARCH_Z196)
.long 2, 0xc100efe3, 0xf46c0000
#elif defined(CONFIG_MARCH_Z10)