patches for DPDK stable branches
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From: Pavan Nikhilesh Bhagavatula <pbhagavatula@marvell.com>
To: Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>,
	"dev@dpdk.org" <dev@dpdk.org>,
	Jerin Jacob Kollanukkaran <jerinj@marvell.com>,
	"hemant.agrawal@nxp.com" <hemant.agrawal@nxp.com>,
	"akhil.goyal@nxp.com" <akhil.goyal@nxp.com>,
	"ogerlitz@mellanox.com" <ogerlitz@mellanox.com>,
	"ajit.khaparde@broadcom.com" <ajit.khaparde@broadcom.com>
Cc: "ruigeng.wang@arm.com" <ruigeng.wang@arm.com>,
	"dharmik.thakkar@arm.com" <dharmik.thakkar@arm.com>,
	"phil.yang@arm.com" <phil.yang@arm.com>,
	"stable@dpdk.org" <stable@dpdk.org>
Subject: Re: [dpdk-stable] [dpdk-dev] [PATCH] eal: generic counter based loop for CPU freq	calculation
Date: Wed, 24 Jun 2020 15:09:24 +0000
Message-ID: <BN6PR18MB11401E50F1D39BA36262A246DE950@BN6PR18MB1140.namprd18.prod.outlook.com> (raw)
In-Reply-To: <20200608213417.9764-1-honnappa.nagarahalli@arm.com>

>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


  parent reply	other threads:[~2020-06-24 15:09 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-08 21:34 [dpdk-stable] " Honnappa Nagarahalli
2020-06-24 12:50 ` [dpdk-stable] [dpdk-dev] " Jerin Jacob
2020-06-26 20:46   ` Honnappa Nagarahalli
2020-06-24 15:09 ` Pavan Nikhilesh Bhagavatula [this message]
2020-06-26 20:35 ` [dpdk-stable] [PATCH v2 1/2] eal/arm: " Honnappa Nagarahalli
2020-07-07 11:16   ` [dpdk-stable] [dpdk-dev] " David Marchand

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