[dpdk-dev] [PATCH] ring: guarantee ordering of cons/prod loading when doing enqueue/dequeue
hejianet at gmail.com
Fri Nov 3 03:55:40 CET 2017
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?
>> + *old_head = __atomic_load_n(&r->cons.head, __ATOMIC_ACQUIRE);
>> + const uint32_t prod_tail = __atomic_load_n(&r->prod.tail,
>> It would be nice to see how much overhead it gives.ie back to back
> 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.
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)
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?
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.
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