[dpdk-users] 1518B of 1G NIC can't achieve 100% throughput

[MESSI SHIYEH <shiyehgo@gmail.com>]

Hi all,

I have a bay trail platform as shown below:
 ===============================================
||  Atom N2807 --> PCIE Switch --> Intel I210 --> RJ45 Eth1    ||
||                                                     |
                                   ||
||                                                     | --> Intel I210 -->
RJ45 Eth2    ||
 ===============================================

Now I run RFC2544 throughput test for Linux native ip forwarding,
and get the result as show below:
================================
||  Frame Size(bytes)  ||  Throughput(%)  ||
||                         1518   ||  100                      ||
================================
Focus on 1518B, the throughput is totally 100%.

However, I run RFC2544 test with DPDK (testpmd),
and here is the result.
================================
||  Frame Size(bytes)  ||  Throughput(%)   ||
||                        1518    ||  99.297                 ||
================================
(My command is: #./testpmd -c 0x3 -n 1 -- -i --nb-cores=1 --nb-ports=2
--total-num-mbufs=2048)
The throughput of 1518B is just only 99.297%,
which means it is failed when running 100% offered loading because there is
a few frame loss (~0.5%).

Could anyone help us to explain the phenomenon?
Could anyone help us to improve it to 100%?

BTW, I just attempted to modify these parameters like rxd, txd, txwt,
burst, etc,..
but it doesn't seem work to me.

PS.

OS: CentOS 7.1 x64

Kernel: 3.10.0-229

DPDK ver: 16.04


BR,

Leo,