Hello,

I want to use hairpin queues to forward high priority traffic (such as 
LACP).
My goal is to ensure that this traffic is not dropped in case the 
software pipeline is overwhelmed.
But during testing with dpdk-testpmd I can't achieve full throughput for 
hairpin queues.

The best result I have been able to achieve for 64B packets is 83 Gbps 
in this configuration:
$ sudo dpdk-testpmd -l 0-1 -n 4 -a 0000:17:00.0,hp_buf_log_sz=19 -- 
--rxq=1 --txq=1 --rxd=4096 --txd=4096 --hairpinq=2
testpmd> flow create 0 ingress pattern eth src is 00:10:94:00:00:03 / 
end actions rss queues 1 2 end / end

For packets in the range 68-80B I measured even lower throughput.
Full throughput I measured only from packets larger than 112B

For only one queue, I didn't get more than 55Gbps:
$ sudo dpdk-testpmd -l 0-1 -n 4 -a 0000:17:00.0,hp_buf_log_sz=19 -- 
--rxq=1 --txq=1 --rxd=4096 --txd=4096 --hairpinq=1 -i
testpmd> flow create 0 ingress pattern eth src is 00:10:94:00:00:03 / 
end actions queue index 1 / end

I tried to use locked device memory for TX and RX queues, but it seems 
that this is not supported:
"--hairpin-mode=0x011000" (bit 16 - hairpin TX queues will use locked 
device memory, bit 12 - hairpin RX queues will use locked device memory)

I was expecting that achieving full throughput with hairpin queues would 
not be a problem.
Is my expectation too optimistic?

What other parameters besides 'hp_buf_log_sz' can I use to achieve full 
throughput?
I tried combining the following parameters: mprq_en=, rxqs_min_mprq=, 
mprq_log_stride_num=, txq_inline_mpw=, rxq_pkt_pad_en=,
but with no positive impact on throughput.

My setup:
DPDK version: commit 76cef1af8bdaeaf67a5c4ca5df3f221df994dc46 (HEAD -> 
main, origin/main, origin/HEAD) Date: Wed Apr 3 11:23:20 2024 -0700
OFED version: MLNX_OFED_LINUX-23.10-0.5.5.0 (OFED-23.10-0.5.5)
ConnectX-6 device: 0000:17:00.0 'MT2892 Family [ConnectX-6 Dx] 101d' 
if=ens1f0np0 drv=mlx5_core unused=
PCIe version: 4.0
OS: Oracle Linux Server 8.10

Any guidance or suggestions on how to achieve full throughput would be 
greatly appreciated.

Thank you,
Mário Kuka