Commit 4ae80325 authored by Heiko Carstens's avatar Heiko Carstens Committed by Martin Schwidefsky
Browse files

s390/bitops: optimize set_bit() for constant values 



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: default avatarHeiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: default avatarMartin Schwidefsky <schwidefsky@de.ibm.com>
parent 370b0b5f

arch/s390/include/asm/bitops.h

+36 −0
Original line number Diff line number Diff line
@@ -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);

}

arch/s390/kernel/head.S

+1 −1
Original line number Diff line number Diff line
@@ -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)

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