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Commit be5e610c authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
Browse files

math64: Add mul_u64_u32_shr() 



Introduce mul_u64_u32_shr() as proposed by Andy a while back; it
allows using 64x64->128 muls on 64bit archs and recent GCC
which defines __SIZEOF_INT128__ and __int128.

(This new method will be used by the scheduler.)

Signed-off-by: default avatarPeter Zijlstra <peterz@infradead.org>
Cc: fweisbec@gmail.com
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/n/tip-hxjoeuzmrcaumR0uZwjpe2pv@git.kernel.org


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent ba1f14fb

arch/x86/Kconfig

+1 −0
Original line number Diff line number Diff line
@@ -26,6 +26,7 @@ config X86 
	select HAVE_AOUT if X86_32

	select HAVE_UNSTABLE_SCHED_CLOCK

	select ARCH_SUPPORTS_NUMA_BALANCING

	select ARCH_SUPPORTS_INT128 if X86_64

	select ARCH_WANTS_PROT_NUMA_PROT_NONE

	select HAVE_IDE

	select HAVE_OPROFILE

include/linux/math64.h

+30 −0
Original line number Diff line number Diff line
@@ -133,4 +133,34 @@ __iter_div_u64_rem(u64 dividend, u32 divisor, u64 *remainder) 
	return ret;

}



#if defined(CONFIG_ARCH_SUPPORTS_INT128) && defined(__SIZEOF_INT128__)



#ifndef mul_u64_u32_shr

static inline u64 mul_u64_u32_shr(u64 a, u32 mul, unsigned int shift)

{

	return (u64)(((unsigned __int128)a * mul) >> shift);

}

#endif /* mul_u64_u32_shr */



#else



#ifndef mul_u64_u32_shr

static inline u64 mul_u64_u32_shr(u64 a, u32 mul, unsigned int shift)

{

	u32 ah, al;

	u64 ret;



	al = a;

	ah = a >> 32;



	ret = ((u64)al * mul) >> shift;

	if (ah)

		ret += ((u64)ah * mul) << (32 - shift);



	return ret;

}

#endif /* mul_u64_u32_shr */



#endif



#endif /* _LINUX_MATH64_H */

init/Kconfig

+6 −0
Original line number Diff line number Diff line
@@ -809,6 +809,12 @@ config GENERIC_SCHED_CLOCK 
config ARCH_SUPPORTS_NUMA_BALANCING

	bool



#

# For architectures that know their GCC __int128 support is sound

#

config ARCH_SUPPORTS_INT128

	bool



# For architectures that (ab)use NUMA to represent different memory regions

# all cpu-local but of different latencies, such as SuperH.

#