From c32ffce0f66e5d1d4856254516e24f5ef275cd00 Mon Sep 17 00:00:00 2001 From: Will Deacon Date: Fri, 21 Feb 2014 17:01:48 +0100 Subject: ARM: 7984/1: prefetch: add prefetchw invocations for barriered atomics After a bunch of benchmarking on the interaction between dmb and pldw, it turns out that issuing the pldw *after* the dmb instruction can give modest performance gains (~3% atomic_add_return improvement on a dual A15). This patch adds prefetchw invocations to our barriered atomic operations including cmpxchg, test_and_xxx and futexes. Signed-off-by: Will Deacon Signed-off-by: Russell King --- arch/arm/include/asm/atomic.h | 9 +++++++++ arch/arm/include/asm/cmpxchg.h | 6 ++++++ arch/arm/include/asm/futex.h | 3 +++ arch/arm/lib/bitops.h | 5 +++++ 4 files changed, 23 insertions(+) (limited to 'arch/arm') diff --git a/arch/arm/include/asm/atomic.h b/arch/arm/include/asm/atomic.h index 62d2cb53b069..6e410090896e 100644 --- a/arch/arm/include/asm/atomic.h +++ b/arch/arm/include/asm/atomic.h @@ -60,6 +60,7 @@ static inline int atomic_add_return(int i, atomic_t *v) int result; smp_mb(); + prefetchw(&v->counter); __asm__ __volatile__("@ atomic_add_return\n" "1: ldrex %0, [%3]\n" @@ -99,6 +100,7 @@ static inline int atomic_sub_return(int i, atomic_t *v) int result; smp_mb(); + prefetchw(&v->counter); __asm__ __volatile__("@ atomic_sub_return\n" "1: ldrex %0, [%3]\n" @@ -121,6 +123,7 @@ static inline int atomic_cmpxchg(atomic_t *ptr, int old, int new) unsigned long res; smp_mb(); + prefetchw(&ptr->counter); do { __asm__ __volatile__("@ atomic_cmpxchg\n" @@ -299,6 +302,7 @@ static inline long long atomic64_add_return(long long i, atomic64_t *v) unsigned long tmp; smp_mb(); + prefetchw(&v->counter); __asm__ __volatile__("@ atomic64_add_return\n" "1: ldrexd %0, %H0, [%3]\n" @@ -340,6 +344,7 @@ static inline long long atomic64_sub_return(long long i, atomic64_t *v) unsigned long tmp; smp_mb(); + prefetchw(&v->counter); __asm__ __volatile__("@ atomic64_sub_return\n" "1: ldrexd %0, %H0, [%3]\n" @@ -364,6 +369,7 @@ static inline long long atomic64_cmpxchg(atomic64_t *ptr, long long old, unsigned long res; smp_mb(); + prefetchw(&ptr->counter); do { __asm__ __volatile__("@ atomic64_cmpxchg\n" @@ -388,6 +394,7 @@ static inline long long atomic64_xchg(atomic64_t *ptr, long long new) unsigned long tmp; smp_mb(); + prefetchw(&ptr->counter); __asm__ __volatile__("@ atomic64_xchg\n" "1: ldrexd %0, %H0, [%3]\n" @@ -409,6 +416,7 @@ static inline long long atomic64_dec_if_positive(atomic64_t *v) unsigned long tmp; smp_mb(); + prefetchw(&v->counter); __asm__ __volatile__("@ atomic64_dec_if_positive\n" "1: ldrexd %0, %H0, [%3]\n" @@ -436,6 +444,7 @@ static inline int atomic64_add_unless(atomic64_t *v, long long a, long long u) int ret = 1; smp_mb(); + prefetchw(&v->counter); __asm__ __volatile__("@ atomic64_add_unless\n" "1: ldrexd %0, %H0, [%4]\n" diff --git a/arch/arm/include/asm/cmpxchg.h b/arch/arm/include/asm/cmpxchg.h index df2fbba7efc8..abb2c3769b01 100644 --- a/arch/arm/include/asm/cmpxchg.h +++ b/arch/arm/include/asm/cmpxchg.h @@ -2,6 +2,7 @@ #define __ASM_ARM_CMPXCHG_H #include +#include #include #if defined(CONFIG_CPU_SA1100) || defined(CONFIG_CPU_SA110) @@ -35,6 +36,7 @@ static inline unsigned long __xchg(unsigned long x, volatile void *ptr, int size #endif smp_mb(); + prefetchw((const void *)ptr); switch (size) { #if __LINUX_ARM_ARCH__ >= 6 @@ -138,6 +140,8 @@ static inline unsigned long __cmpxchg(volatile void *ptr, unsigned long old, { unsigned long oldval, res; + prefetchw((const void *)ptr); + switch (size) { #ifndef CONFIG_CPU_V6 /* min ARCH >= ARMv6K */ case 1: @@ -230,6 +234,8 @@ static inline unsigned long long __cmpxchg64(unsigned long long *ptr, unsigned long long oldval; unsigned long res; + prefetchw(ptr); + __asm__ __volatile__( "1: ldrexd %1, %H1, [%3]\n" " teq %1, %4\n" diff --git a/arch/arm/include/asm/futex.h b/arch/arm/include/asm/futex.h index 2aff798fbef4..53e69dae796f 100644 --- a/arch/arm/include/asm/futex.h +++ b/arch/arm/include/asm/futex.h @@ -23,6 +23,7 @@ #define __futex_atomic_op(insn, ret, oldval, tmp, uaddr, oparg) \ smp_mb(); \ + prefetchw(uaddr); \ __asm__ __volatile__( \ "1: ldrex %1, [%3]\n" \ " " insn "\n" \ @@ -46,6 +47,8 @@ futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr, return -EFAULT; smp_mb(); + /* Prefetching cannot fault */ + prefetchw(uaddr); __asm__ __volatile__("@futex_atomic_cmpxchg_inatomic\n" "1: ldrex %1, [%4]\n" " teq %1, %2\n" diff --git a/arch/arm/lib/bitops.h b/arch/arm/lib/bitops.h index 52886b89706c..9f12ed1eea86 100644 --- a/arch/arm/lib/bitops.h +++ b/arch/arm/lib/bitops.h @@ -37,6 +37,11 @@ UNWIND( .fnstart ) add r1, r1, r0, lsl #2 @ Get word offset mov r3, r2, lsl r3 @ create mask smp_dmb +#if __LINUX_ARM_ARCH__ >= 7 && defined(CONFIG_SMP) + .arch_extension mp + ALT_SMP(W(pldw) [r1]) + ALT_UP(W(nop)) +#endif 1: ldrex r2, [r1] ands r0, r2, r3 @ save old value of bit \instr r2, r2, r3 @ toggle bit -- cgit v1.2.3-59-g8ed1b