On 11/30/2015 07:53 PM, Richardson, Bruce wrote:

quoted

-----Original Message-----
From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Alexey Bogdanenko
Sent: Monday, November 30, 2015 4:17 PM
To: dev@dpdk.org
Subject: [dpdk-dev] Unable to configure ethdev in secondary process using
ring PMD

Hello,

I would like to setup communication between two existing DPDK applications
and run them on the same host.

"Connecting their ports" in some way in order not to rewrite the
applications would be very desirable. Specifically, I would like one
process to send packets and the second process to receive the packets
using rte_eth_tx_burst() and rte_eth_rx_burst() respectively.

The most straightforward way to accomplish this seems to be by using ring
based PMD API as described in the documentation [1] and email [2].
To adapt the example from the documentation to multi-process scenario, I
call rte_ring_create() and rte_eth_from_rings() in the primary process,
rte_ring_lookup() and rte_eth_from_rings() in the secondary process.
After that each process calls rte_eth_dev_configure().

Unfortunately, the function returns -1001 in the secondary process, which
is explained in debug log:

PMD: rte_eth_dev_configure: Cannot run in secondary processes

Is it possible to connect the applications as described above? Any advice
would be appreciated.

References:

1. Network Interface Controller Drivers. Chapter 8.
Libpcap and Ring Based Poll Mode Drivers.

2. DPDK ML. Fri Dec 6 07:22:06 CET 2013. How to know corresponding device
from port number. Tetsuya.Mukawa

Thanks,

Alexey Bogdanenko

Hi Alexey,

The ring PMDs returned from eth_from_rings should be all ready to be used without having to explicitly configure it or set up the queues.

/Bruce

Thanks for the quick reply,

I updated dpdk from v2.1.0 to a more recent version (near v2.2.0-rc2), 
removed calls to rte_eth_dev_configure(), rte_eth_rx_queue_setup(). It 
solved the problem.

Your advice was very helpful.

However, I encountered a rather minor but similar issue, which is that
rte_eth_dev_start() returns -1001 in the secondary processes. The 
message I get is:

rte_eth_dev_start: Cannot run in secondary processes

Now, I could avoid calling the function altogether, however in this case
rte_eth_link_get_nowait() reports that the link status is down which is 
a bit inconvenient.

Did I miss anything or is it just a limitation of ring PMD?

Alexey Bogdanenko