From: Jerin Jacob <jerinjacobk@gmail.com> To: Honnappa Nagarahalli <honnappa.nagarahalli@arm.com> Cc: dpdk-dev <dev@dpdk.org>, Jerin Jacob <jerinj@marvell.com>, Hemant Agrawal <hemant.agrawal@nxp.com>, Akhil Goyal <akhil.goyal@nxp.com>, ogerlitz@mellanox.com, Ajit Khaparde <ajit.khaparde@broadcom.com>, ruigeng.wang@arm.com, Dharmik Thakkar <dharmik.thakkar@arm.com>, Phil Yang <phil.yang@arm.com>, dpdk stable <stable@dpdk.org> Subject: Re: [dpdk-dev] [PATCH] eal: generic counter based loop for CPU freq calculation Date: Wed, 24 Jun 2020 18:20:54 +0530 Message-ID: <CALBAE1PmPiDf+54NkNSfs7sztANdxnU+1M3a1YaZHMGZe27thg@mail.gmail.com> (raw) In-Reply-To: <20200608213417.9764-1-honnappa.nagarahalli@arm.com> On Tue, Jun 9, 2020 at 3:04 AM Honnappa Nagarahalli <honnappa.nagarahalli@arm.com> wrote: > > get_tsc_freq uses 'nanosleep' system call to calculate the CPU > frequency. However, 'nanosleep' results in the process getting > un-scheduled. The kernel saves and restores the PMU state. This > ensures that the PMU cycles are not counted towards a sleeping > process. When RTE_ARM_EAL_RDTSC_USE_PMU is defined, this results > in incorrect CPU frequency calculation. This logic is replaced > with generic counter based loop. > > Bugzilla ID: 450 > Fixes: af75078fece3 ("first public release") The Fix looks good to me. The Fixes is not correct. It should be the patch where RTE_ARM_EAL_RDTSC_USE_PMU got introduced. > Cc: stable@dpdk.org > > Signed-off-by: Honnappa Nagarahalli <honnappa.nagarahalli@arm.com> > Reviewed-by: Ruifeng Wang <ruifeng.wang@arm.com> > Reviewed-by: Dharmik Thakkar <dharmik.thakkar@arm.com> > Reviewed-by: Phil Yang <phil.yang@arm.com> > > --- > lib/librte_eal/arm/include/rte_cycles_64.h | 45 +++++++++++++++++++--- > lib/librte_eal/arm/rte_cycles.c | 24 ++++++++++-- > 2 files changed, 61 insertions(+), 8 deletions(-) > > diff --git a/lib/librte_eal/arm/include/rte_cycles_64.h b/lib/librte_eal/arm/include/rte_cycles_64.h > index da557b6a1..6fc352036 100644 > --- a/lib/librte_eal/arm/include/rte_cycles_64.h > +++ b/lib/librte_eal/arm/include/rte_cycles_64.h > @@ -11,6 +11,36 @@ extern "C" { > > #include "generic/rte_cycles.h" > > +/** Read generic counter frequency */ > +static inline uint64_t I prefer to have __rte_allways_inline > +__rte_rd_generic_cntr_freq(void) I think, the generic counter is confusing, I think, since the symbol is exposed due to placed in header file, it is better to change, __rte_arm64_cntfrq() > +{ > + uint64_t freq; > + > + asm volatile("mrs %0, cntfrq_el0" : "=r" (freq)); > + return freq; > +} > + > +/** Read generic counter */ > +static inline uint64_t Likewise, __rte_arm64_cntvct() > +__rte_rd_generic_cntr(void) > +{ > + uint64_t tsc; > + > + asm volatile("mrs %0, cntvct_el0" : "=r" (tsc)); > + return tsc; > +} > + > +static inline uint64_t > +__rte_rd_generic_cntr_precise(void) __rte_arm64_cntfrq_precise() > +{ > + uint64_t tsc; > + > + asm volatile("isb" : : : "memory"); > + asm volatile("mrs %0, cntvct_el0" : "=r" (tsc)); > + return tsc; > +} > + > /** > * Read the time base register. > * > @@ -25,10 +55,7 @@ extern "C" { > static inline uint64_t > rte_rdtsc(void) > { > - uint64_t tsc; > - > - asm volatile("mrs %0, cntvct_el0" : "=r" (tsc)); > - return tsc; > + return __rte_rd_generic_cntr(); > } > #else > /** > @@ -49,14 +76,22 @@ rte_rdtsc(void) > * asm volatile("msr pmcr_el0, %0" : : "r" (val)); > * > */ > + > +/** Read PMU cycle counter */ > static inline uint64_t > -rte_rdtsc(void) > +__rte_rd_pmu_cycle_cntr(void) > { > uint64_t tsc; > > asm volatile("mrs %0, pmccntr_el0" : "=r"(tsc)); > return tsc; > } > + > +static inline uint64_t > +rte_rdtsc(void) > +{ > + return __rte_rd_pmu_cycle_cntr(); > +} > #endif > > static inline uint64_t > diff --git a/lib/librte_eal/arm/rte_cycles.c b/lib/librte_eal/arm/rte_cycles.c > index 3500d523e..92c87a8a4 100644 > --- a/lib/librte_eal/arm/rte_cycles.c > +++ b/lib/librte_eal/arm/rte_cycles.c > @@ -3,14 +3,32 @@ > */ > > #include "eal_private.h" > +#include "rte_cycles.h" > > uint64_t > get_tsc_freq_arch(void) > { > #if defined RTE_ARCH_ARM64 && !defined RTE_ARM_EAL_RDTSC_USE_PMU > - uint64_t freq; > - asm volatile("mrs %0, cntfrq_el0" : "=r" (freq)); > - return freq; > + return __rte_rd_generic_cntr_freq(); > +#elif defined RTE_ARCH_ARM64 && defined RTE_ARM_EAL_RDTSC_USE_PMU > + /* Use the generic counter ticks to calculate the PMU > + * cycle frequency. > + */ > + uint64_t gcnt_ticks; > + uint64_t start_ticks, cur_ticks; > + uint64_t start_pmu_cycles, end_pmu_cycles; > + > + /* Number of ticks for 1/10 second */ > + gcnt_ticks = __rte_rd_generic_cntr_freq() / 10; > + > + start_ticks = __rte_rd_generic_cntr_precise(); > + start_pmu_cycles = rte_rdtsc_precise(); > + do { > + cur_ticks = __rte_rd_generic_cntr(); > + } while ((cur_ticks - start_ticks) < gcnt_ticks); > + end_pmu_cycles = rte_rdtsc_precise(); > + > + return ((end_pmu_cycles - start_pmu_cycles) * 10); Good thought. On the plus side, it will reduce the boot time by .9 sec. > #else > return 0; With above changes: Acked-by: Jerin Jacob <jerinj@marvell.com> > #endif > -- > 2.17.1 >
next prev parent reply other threads:[~2020-06-24 12:51 UTC|newest] Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-06-08 21:34 Honnappa Nagarahalli 2020-06-24 12:50 ` Jerin Jacob [this message] 2020-06-26 20:46 ` Honnappa Nagarahalli 2020-06-24 15:09 ` Pavan Nikhilesh Bhagavatula 2020-06-26 20:35 ` [dpdk-dev] [PATCH v2 1/2] eal/arm: " Honnappa Nagarahalli 2020-06-26 20:35 ` [dpdk-dev] [PATCH v2 2/2] eal/arm: change inline functions to always inline Honnappa Nagarahalli 2020-07-07 2:05 ` Jerin Jacob 2020-07-07 11:16 ` [dpdk-dev] [PATCH v2 1/2] eal/arm: generic counter based loop for CPU freq calculation David Marchand
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