DPDK little frame loss

Hi,

I have a RFC2544 throughput test on Ivy Bridge platform (which CPU is i7-3770, NIC chip is 82574) by Spirent Test Center, when DUT is running DPDK example l2fwd; It's confusing that it always has a little "frame loss", no matter what is the packet size, even 1518 bytes. I wonder what caused it. The following is test result. Please give me some suggestion, many thanks!

PS,

1.When DUT tested, I have closed some power consumption options, for example Cx-states, ASPM, EIST, ...

2.I have tried to add kernel parameter "isolcpus" to isolate cores from the general scheduler.

3.I find that the haswell platform(cpu=i7-4790S, NIC chip=i350) and bay trail platform have the same trouble as above.

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Best Regards,

Leon