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

[Stephen Hemminger]

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!