In order to get more accurate the cntvct_el0 reading, SW must invoke isb and arch_counter_enforce_ordering.
Reference of linux kernel: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/arm64/include/asm/arch_timer.h?h=v5.5#n220 Signed-off-by: Haifeng Lin <haifeng....@huawei.com> --- .../common/include/arch/arm/rte_atomic_64.h | 3 +++ .../common/include/arch/arm/rte_cycles_64.h | 20 +++++++++++++++++-- 2 files changed, 21 insertions(+), 2 deletions(-) diff --git a/lib/librte_eal/common/include/arch/arm/rte_atomic_64.h b/lib/librte_eal/common/include/arch/arm/rte_atomic_64.h index 859ae129d..2587f98a2 100644 --- a/lib/librte_eal/common/include/arch/arm/rte_atomic_64.h +++ b/lib/librte_eal/common/include/arch/arm/rte_atomic_64.h @@ -21,6 +21,7 @@ extern "C" { #define dsb(opt) asm volatile("dsb " #opt : : : "memory") #define dmb(opt) asm volatile("dmb " #opt : : : "memory") +#define isb() (asm volatile("isb" : : : "memory")) #define rte_mb() dsb(sy) @@ -44,6 +45,8 @@ extern "C" { #define rte_cio_rmb() dmb(oshld) +#define rte_isb() isb() + /*------------------------ 128 bit atomic operations -------------------------*/ #if defined(__ARM_FEATURE_ATOMICS) || defined(RTE_ARM_FEATURE_ATOMICS) diff --git a/lib/librte_eal/common/include/arch/arm/rte_cycles_64.h b/lib/librte_eal/common/include/arch/arm/rte_cycles_64.h index 68e7c7338..bc4e3f8e6 100644 --- a/lib/librte_eal/common/include/arch/arm/rte_cycles_64.h +++ b/lib/librte_eal/common/include/arch/arm/rte_cycles_64.h @@ -18,6 +18,7 @@ extern "C" { * The time base for this lcore. */ #ifndef RTE_ARM_EAL_RDTSC_USE_PMU + /** * This call is portable to any ARMv8 architecture, however, typically * cntvct_el0 runs at <= 100MHz and it may be imprecise for some tasks. @@ -59,11 +60,26 @@ rte_rdtsc(void) } #endif +#define arch_counter_enforce_ordering(val) do { \ + uint64_t tmp, _val = (val); \ + \ + asm volatile( \ + " eor %0, %1, %1\n" \ + " add %0, sp, %0\n" \ + " ldr xzr, [%0]" \ + : "=r" (tmp) : "r" (_val)); \ +} while (0) + + static inline uint64_t rte_rdtsc_precise(void) { - rte_mb(); - return rte_rdtsc(); + uint64_t tsc; + + rte_isb(); + tsc = rte_rdtsc(); + arch_counter_enforce_ordering(tsc); + return tsc; } static inline uint64_t -- 2.24.1.windows.2
