[dpdk-users] Link Status App

De Lara Guarch, Pablo pablo.de.lara.guarch at intel.com
Wed Apr 27 16:24:20 CEST 2016


> -----Original Message-----
> From: users [mailto:users-bounces at dpdk.org] On Behalf Of Gadre Nayan
> Sent: Wednesday, April 27, 2016 3:08 PM
> To: users at dpdk.org
> Subject: [dpdk-users] Link Status App
> Dear All,
> I have started with DPDK library. I have some terminology related questions.
> 1. What are "lcores":
>    My system has 2 sockets and 6 cores per socket. Are these internal
> cores --> lcores?
>    So then my system will have 12 lcores?

If your system has Hyperthreading (considering it is Intel), your CPU will have two logical cores per physical core
(so you can run two threads simultaneously per physical core).
In your case, you have logical 24 cores (2 sockets x 6 cores/socket x 2 logical cores/physical core).

> 2. I am trying to work on the Link status change application.
> I am confused with the terminology, having not much experience, So
> here is the confusion.
> I have the compiled application: link_status.
> ./link_status -c f -n 4-- -q 8 -p 0x0f
> Here I am setting the portmask as 0x0F as I am going to use 4 ports.
> Next -q NQ: A number of queues (=ports) per lcore (default is 1)

As stated in the help, "q" parameter sets the number of queues that will be handled by a single core.
So, if using -q 1 with 4 ports, you will need 4 cores. If you want to use only 1 core, then you should use -q 4.
From your command line, -q 8 is too high, as you will have only 4 ports (therefore, only 4 queues, see below).
> So I donot get the ( number of queues = ports ) statement here.

Basically, this app configures only 1 queue per port, so the number of queues are equal to the number of ports.
> Network cards have RX and TX queues, I have a card which has 7 RX and
> TX queues. Also my NIC has 4 ports. So each port will have 7 RX and TX
> queues.

Wow, odd number of queues :P Anyway, usually number of queues are per port,
so yes, each port will have 7 RX/TX queues. Just mind that the link_status app only configures the first queue per port.

> So how is this statement (number of queues = ports) per lcore (default
> is 1) valid. What should be the argument in my case.
> Please explain.
> Thanks

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