Re: [dpdk-users] Low TX performance on Mellanox ConnectX-3 NIC

["Wiles, Keith" <keith.wiles@intel.com>]

On 10/31/15, 3:54 AM, "users on behalf of Jesper Wramberg" <users-bounces@dpdk.org on behalf of jesper.wramberg@gmail.com> wrote:

>Hi all,
>
>
>
>I am experiencing some performance issues in a somewhat custom setup with
>two Mellanox ConnectX-3 NICs. I realize these issues might be due to the
>setup, but I was hoping someone might be able to pinpoint some possible
>problems/bottlenecks.
>
>
>
>
>The server:
>
>I have a Dell PowerEdge R630 with two Mellanox ConnectX-3 NICs (one on each
>socket). I have a minimal Centos 7.1.1503 installed with kernel-3.10.0-229.
>Note that this kernel is re-build with most things disabled to minimize
>size, etc. It has infiniband enabled, however, and mlx4_core as a module
>(since nothing works otherwise). Finally, I have connected the two NICs
>from port 2 to port 2.
>
>
>
>The firmware:
>
>I have installed the latest firmware for the NICs from dell which is
>2.34.5060.
>
>
>
>The drivers, modules, etc.:
>
>I have downloaded the Mellanox OFED package 3.1 for Centos 7.1 and used its
>rebuild feature to build it against the custom kernel. I have installed it
>using the --basic option since I just want libibverbs, libmlx4, kernel
>modules and openibd service stuff. The mlx4_core.conf is set for ethernet
>on all ports. Moreover, it is configured for flow steering mode -7 and a
>few VFs. I can restart the openibd service successfully and everything
>seems to be working. ibdev2netdev reports the NICs and its VFs, etc. The
>only problems I have encountered at this stage is that the links doesn't
>always seem to come up unless I unplug and re-plug the cables.
>
>
>
>DPDK setup:
>
>I have built DPDK with the mlx4 pmd using the .h/.a files from the OFED
>package. I build it using the default values for everything. Running the
>simple hello world example I can see that everything is initialized
>correctly, etc.
>
>
>
>Test setup:
>
>To test the performance of the NICs I have the following setup. Two
>processes, P1 and P2, running on NIC A. Two other processes, P3 and P4,
>running on NIC B. All processes use virtual functions on their respective
>NICs. Depending on the test, the processes can either transmit or receive
>data. To transmit, I use a simple DPDK program which generates 32000
>packets and transmits them over and over until it has sent 640 million
>packets. Similarly, I use a simple DPDK program to receive which is
>basically the layer 2 forwarding example without re-transmission.
>
>
>
>First test:
>
>In my first test, P1 transmits data to P3 while the other processes are
>idle.
>
>Packet size: 1480 byte packets
>
>Flow control: On/Off, doesn’t matter I get same result.
>
>Result: P3 receive all packets but it takes 192.52 seconds ~ 3.32 Mpps ~
>4.9Gbit/s
>
>
>
>Second test:
>
>I my second test, I attempt to increase the amount of data transmitted over
>NIC A. As such, P1 transmits data to P3 while P2 transmits data to P4.
>
>Packet size: 1480 byte packets
>
>Flow control: On/Off, doesn’t matter I get same result.
>
>Results: P3 and P4 receive all packets but it takes 364.40 seconds ~ 1.75
>Mpps ~ 2.6Gbit/s for a single process to get its data transmitted.
>

One suggestion I have would be to split the problem into two parts by looping the cable or packets back to the machine sending the packets and see what the performance is in that case. The other possible suggestion is to try Pktgen-dpdk on the two machines with the cables looped back to them selves and see what Pktgen performance is in that case. I do not know what the problem is I am only suggesting you try some applications we know work and simplify the configuration. I hope this helps.
>
>
>
>
>Does anyone has any idea what I am doing wrong here ? In the second test I
>would expect P1 to transmit with the same speed as in the first test. It
>seems that there is a bottleneck somewhere, however. I have left most
>things to their default values but have also tried tweaking queue sizes,
>number of queues, interrupts, etc. with no luck
>
>
>
>
>
>Best Regards,
>
>Jesper
>


Regards,
Keith