Low bandwidth using DPDK2.2 and pktgen-dpdk on ConnectX-3

Hello,

I’m trying a very simple setup connecting a ConnectX-3 card on one host directly to another ConnectX-3 card on another. I’m using DPDK 2.2 and pktgen-2.9.7 to send packets from one to another. I have configured both sending and receiving ports to Ethernet.

Things are functional, I can saturate 40Gb/s with packet sizes of 1024 or 512 bytes but not with 256 bytes or lower. Seems like the max throughput I get is 12 Mpps.

I verified that I have set log_num_mgm_entry_size=-7.

This is my pktgen command line: pktgen -c 0xFFF00 -n 4 -w 0000:82:00.0 -m 2048 – -T -P -p 0x0 -m “[10-11:12-13].0”

Any idea why I can’t saturate the line with small packets? Any help would be greatly appreciated.

Hi Olga,

Thanks for your comments. Burst size is set to 32 by default, at least when I try it on 82599 or ConnectX-3. And it can be modified using "set <port#> burst " command in pktgen. Pktgen doesn’t accept a value larger than 32 for the burst size (unless I recompile the source code obviously as you mentioned). However, regardless of whether I set the burst size to 1 or 32, I still get the same ~12 Mpps.

Regards,

–Salem

Hi,

In matter of fact we didn’t run performance tests with pktgen.

You can try to change rxq, txq and burst size.

In the past I have tried to check if it can be done dynamically with pktgen, but didn’t find a way.

Changed the following values in app/pktgen-constants.h

DEFAULT_PKT_BURST = 64, // Increasing this number consumes memory very fast

//#ifdef RTE_LIBRTE_VMXNET3_PMD

// DEFAULT_RX_DESC = (DEFAULT_PKT_BURST * 8 * 2),

// DEFAULT_TX_DESC = DEFAULT_RX_DESC,

//#else

// DEFAULT_RX_DESC = (DEFAULT_PKT_BURST * 8),

// DEFAULT_TX_DESC = DEFAULT_RX_DESC,

DEFAULT_RX_DESC = 256,

DEFAULT_TX_DESC = 256,

//#endif

Try to check TX first …

Hope it helps.

Best Regards,

Olga