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From: Jia He <hejianet@gmail.com>
To: Jerin Jacob <jerin.jacob@caviumnetworks.com>
Cc: "Ananyev, Konstantin" <konstantin.ananyev@intel.com>,
"Zhao, Bing" <ilovethull@163.com>, Olivier MATZ <olivier.matz@6wind.com>,
"dev@dpdk.org" <dev@dpdk.org>,
"jia.he@hxt-semitech.com" <jia.he@hxt-semitech.com>,
"jie2.liu@hxt-semitech.com" <jie2.liu@hxt-semitech.com>,
"bing.zhao@hxt-semitech.com" <bing.zhao@hxt-semitech.com>,
"Richardson, Bruce" <bruce.richardson@intel.com>, jianbo.liu@arm.com,
hemant.agrawal@nxp.com
References: <2601191342CEEE43887BDE71AB9772585FAAB570@IRSMSX103.ger.corp.intel.com>
<3e580cd7-2854-d855-be9c-7c4ce06e3ed5@gmail.com>
<20171020054319.GA4249@jerin>
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<20171025132642.GA13977@jerin>
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<69adfb00-4582-b362-0540-d1d9d6bcf6aa@gmail.com>
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Date: Fri, 3 Nov 2017 10:55:40 +0800
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Subject: Re: [dpdk-dev] [PATCH] ring: guarantee ordering of cons/prod
loading when doing enqueue/dequeue
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Hi Jerin
On 11/2/2017 4:57 PM, Jia He Wrote:
>
> Hi， Jerin
> please see my performance test below
> On 11/2/2017 3:04 AM, Jerin Jacob Wrote:
> [...]
>> Should it be like instead?
>>
>> +#else
>> + *old_head = __atomic_load_n(&r->cons.head, __ATOMIC_ACQUIRE);
>> + const uint32_t prod_tail = __atomic_load_n(&r->prod.tail,
>> __ATOMIC_ACQUIRE);
>> It would be nice to see how much overhead it gives.ie back to back
>> __ATOMIC_ACQUIRE.
> I can NOT test ring_perf_autotest in our server because of the
> something wrong in PMU counter.
> All the return value of rte_rdtsc is 0 with and without your provided
> ko module. I am still
> investigating the reason.
>
Hi Jerin
As for the root cause of rte_rdtsc issue, it might be due to the pmu
counter frequency is too low
in our arm64 server("Amberwing" from qualcom)
[586990.057779] arch_timer_get_cntfrq()=20000000
Only 20MHz instead of 100M/200MHz, and CNTFRQ_EL0 is not even writable
in kernel space.
Maybe the code in ring_perf_autotest needs to be changed?
e.g.
printf("SC empty dequeue: %.2F\n",
(double)(sc_end-sc_start) / iterations);
printf("MC empty dequeue: %.2F\n",
(double)(mc_end-mc_start) / iterations);
Otherwise it is always 0 if the time difference divides by iterations.
--
Cheers,
Jia