[dpdk-dev] IXGBE throughput loss with 4+ cores

[Saber Rezvani]

On 08/28/2018 08:31 PM, Stephen Hemminger wrote:
> On Tue, 28 Aug 2018 17:34:27 +0430
> Saber Rezvani <irsaber at zoho.com> wrote:
>
>> Hi,
>>
>>
>> I have run multi_process/symmetric_mp example in DPDK example directory.
>> For a one process its throughput is line rate but as I increase the
>> number of cores I see decrease in throughput. For example, If the number
>> of queues set to 4 and each queue assigns to a single core, then the
>> throughput will be something about 9.4. if 8 queues, then throughput
>> will be 8.5.
>>
>> I have read the following, but it was not convincing.
>>
>> http://mails.dpdk.org/archives/dev/2015-October/024960.html
>>
>>
>> I am eagerly looking forward to hearing from you, all.
>>
>>
>> Best wishes,
>>
>> Saber
>>
>>
> Not completely surprising. If you have more cores than packet line rate
> then the number of packets returned for each call to rx_burst will be less.
> With large number of cores, most of the time will be spent doing reads of
> PCI registers for no packets!
Indeed pktgen says it is generating traffic at line rate, but receiving 
less than 10 Gb/s. So, it that case there should be something that 
causes the reduction in throughput :(