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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: Peter 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: Ingo Molnar <mingo@kernel.org>
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@ -26,6 +26,7 @@ config X86
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select HAVE_AOUT if X86_32
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select HAVE_UNSTABLE_SCHED_CLOCK
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select ARCH_SUPPORTS_NUMA_BALANCING
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select ARCH_SUPPORTS_INT128 if X86_64
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select ARCH_WANTS_PROT_NUMA_PROT_NONE
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select HAVE_IDE
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select HAVE_OPROFILE
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@ -133,4 +133,34 @@ __iter_div_u64_rem(u64 dividend, u32 divisor, u64 *remainder)
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return ret;
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}
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#if defined(CONFIG_ARCH_SUPPORTS_INT128) && defined(__SIZEOF_INT128__)
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#ifndef mul_u64_u32_shr
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static inline u64 mul_u64_u32_shr(u64 a, u32 mul, unsigned int shift)
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{
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return (u64)(((unsigned __int128)a * mul) >> shift);
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}
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#endif /* mul_u64_u32_shr */
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#else
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#ifndef mul_u64_u32_shr
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static inline u64 mul_u64_u32_shr(u64 a, u32 mul, unsigned int shift)
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{
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u32 ah, al;
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u64 ret;
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al = a;
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ah = a >> 32;
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ret = ((u64)al * mul) >> shift;
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if (ah)
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ret += ((u64)ah * mul) << (32 - shift);
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return ret;
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}
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#endif /* mul_u64_u32_shr */
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#endif
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#endif /* _LINUX_MATH64_H */
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@ -809,6 +809,12 @@ config GENERIC_SCHED_CLOCK
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config ARCH_SUPPORTS_NUMA_BALANCING
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bool
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#
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# For architectures that know their GCC __int128 support is sound
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#
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config ARCH_SUPPORTS_INT128
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bool
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# For architectures that (ab)use NUMA to represent different memory regions
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# all cpu-local but of different latencies, such as SuperH.
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#
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