the packet delay is too long when I used dpdk i40e NIC sent single packet

[Xing, Beilei]

Hi,

Could you try to change interval configuration to check if it helps?
Please refer to i40e_calc_itr_interval function.
In theory, the lower interval, the lower latency.

BR,
Beilei

> -----Original Message-----
> From: jiangheng <jiangheng14 at huawei.com>
> Sent: Wednesday, July 5, 2023 9:33 AM
> To: Zhang, Yuying <yuying.zhang at intel.com>; Xing, Beilei
> <beilei.xing at intel.com>
> Cc: users at dpdk.org
> Subject: the packet delay is too long when I used dpdk i40e NIC sent single
> packet
> 
> Hi Beilei:
> we used dpdk implement a user mode tcp protocol stack, and we are testing
> the delay of a single packet.
> however, on i40e NIC(XL710), the packet delay is higher than that of the kernel.
> After some tests, we find that the time consuming may be the pahse when i40e
> sends packet.(period from rte_eth_tx_burst to packet be sent) The same test is
> performed on the ixgbe(82599) NIC. the delay is lower than that in kernel.
> 
> I used dpdk-21.11 stable version.
> I tried upgrading the i40e's firmware version to 9.10, but there was no
> improvement.
> Any suggestion?
> Thank you.
> 
> 
> 
> The following is packet delay statistics of tcpdump:
> i40e NIC:
> 410	10.373817	192.168.4.4	192.168.4.5	TCP	64	8877
> →58312 [ACK] Seq=6511 Ack=9642 Win=1048384 Len=0
>     10us
> 411	10.373827	192.168.4.4	192.168.4.5	TCP	94	58312
> →8877 [PSH, ACK] Seq=9642 Ack=6511 Win=1048512 Len=36
>     27us
> 412	10.373854	192.168.4.5	192.168.4.4	TCP	60	8877
> →58312 [ACK] Seq=6511 Ack=9678 Win=1048320 Len=0
>     9us
> 413	10.373863	192.168.4.5	192.168.4.4	TCP	90	58312
> →8877 [PSH, ACK] Seq=9642 Ack=6511 Win=1048512 Len=36
>     28us
> 414	10.373891	192.168.4.4	192.168.4.5	TCP	64	8877
> →58312 [ACK] Seq=6511 Ack=9678 Win=1048320 Len=0
>     11us
> 415	10.373902	192.168.4.4	192.168.4.5	TCP	94	58312
> →8877 [PSH, ACK] Seq=9678 Ack=6511 Win=1048512 Len=36
>     28us
> 416	10.373930	192.168.4.5	192.168.4.4	TCP	60	8877
> →58312 [ACK] Seq=6511 Ack=9714 Win=1048320 Len=0
>     11us
> 417	10.373941	192.168.4.5	192.168.4.4	TCP	90	58312
> →8877 [PSH, ACK] Seq=9678 Ack=6511 Win=1048512 Len=36
>     25us
> 418	10.373967	192.168.4.4	192.168.4.5	TCP	64	8877
> →58312 [ACK] Seq=6511 Ack=9714 Win=1048320 Len=0
>     11us
> 419	10.373978	192.168.4.4	192.168.4.5	TCP	94	58312
> →8877 [PSH, ACK] Seq=9714 Ack=6511 Win=1048512 Len=36
>     4us
> 420	10.373982	192.168.4.5	192.168.4.4	TCP	60	8877
> →58312 [ACK] Seq=6511 Ack=9750 Win=1048256 Len=0
> 
> 
> ixgbe NIC:
> 110	13.235208	192.168.4.12	192.168.4.11	TCP	64	8877
> →58312 [ACK] Seq=6511 Ack=7266 Win=1047808 Len=0
>     10us
> 111	13.235218	192.168.4.12	192.168.4.11	TCP	94	58312
> →8877 [PSH, ACK] Seq=7266 Ack=6511 Win=1048512 Len=36
>     6us
> 112	13.235224	192.168.4.11	192.168.4.12	TCP	64	8877
> →58312 [ACK] Seq=6511 Ack=7302 Win=1047744 Len=0
>     10us
> 113	13.235234	192.168.4.11	192.168.4.12	TCP	94	58312
> →8877 [PSH, ACK] Seq=7266 Ack=6511 Win=1048512 Len=36
>     6us
> 114	13.235240	192.168.4.12	192.168.4.11	TCP	64	8877
> →58312 [ACK] Seq=6511 Ack=7302 Win=1047744 Len=0
>     11us
> 115	13.235251	192.168.4.12	192.168.4.11	TCP	94	58312
> →8877 [PSH, ACK] Seq=7302 Ack=6511 Win=1048512 Len=36
>     5us
> 116	13.235256	192.168.4.11	192.168.4.12	TCP	64	8877
> →58312 [ACK] Seq=6511 Ack=7338 Win=1047744 Len=0
>     11us
> 117	13.235267	192.168.4.11	192.168.4.12	TCP	94	58312
> →8877 [PSH, ACK] Seq=7302 Ack=6511 Win=1048512 Len=36
>     6us
> 118	13.235273	192.168.4.12	192.168.4.11	TCP	64	8877
> →58312 [ACK] Seq=6511 Ack=7338 Win=1047744 Len=0
>     10us
> 119	13.235283	192.168.4.12	192.168.4.11	TCP	94	58312
> →8877 [PSH, ACK] Seq=7338 Ack=6511 Win=1048512 Len=36
>     6us
> 120	13.235289	192.168.4.11	192.168.4.12	TCP	64	8877
> →58312 [ACK] Seq=6511 Ack=7374 Win=1047680 Len=0