| Message ID | 20200608213417.9764-1-honnappa.nagarahalli@arm.com |
|---|---|
| State | New |
| Headers | show |
| Series | eal: generic counter based loop for CPU freq calculation | expand |
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 >
>Subject: [dpdk-dev] [PATCH] eal: generic counter based loop for CPU >freq calculation > >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") >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(-) > <Snip> > > 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); I think we need to round this of to the next multiple of 10. Sometimes it is off by one EAL: TSC frequency is ~2399999 KHz Similar to http://git.dpdk.org/dpdk/tree/lib/librte_eal/common/eal_common_timer.c#n54 Pavan. > #else > return 0; > #endif >-- >2.17.1
Hi Jerin, Thanks for the comments. > -----Original Message----- > From: Jerin Jacob <jerinjacobk@gmail.com> > Sent: Wednesday, June 24, 2020 7:51 AM > To: Honnappa Nagarahalli <Honnappa.Nagarahalli@arm.com> > Cc: dpdk-dev <dev@dpdk.org>; jerinj@marvell.com; > hemant.agrawal@nxp.com; Akhil.goyal@nxp.com; ogerlitz@mellanox.com; > Ajit Khaparde (ajit.khaparde@broadcom.com) > <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 > > 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. Ok, will dig that out. > > > > 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() Ok, makes sense. > > > +{ > > + 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) I will change this to __rte_arm64_pmccntr > > { > > 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 > >
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 +__rte_rd_generic_cntr_freq(void) +{ + uint64_t freq; + + asm volatile("mrs %0, cntfrq_el0" : "=r" (freq)); + return freq; +} + +/** Read generic counter */ +static inline uint64_t +__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) +{ + 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); #else return 0; #endif
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") 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(-) -- 2.17.1