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From: Kai Zhang <zhang.4522@osu.edu>
Date: Wed, 23 Jul 2014 15:24:49 -0400
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Subject: [dpdk-dev] About round trip latency with DPDK
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Hello,

I am trying to develop a low-latency application, and I measured the round
trip latency with DPDK. However I got an average of 650~720 microseconds
round-trip latency with Intel 82599 10Gbps NIC.

The experiment method is as follows. 2 machines (A and B) are connected
back-to-back. Machine A embeds a time stamp in the packet and sends to B, B
(use testpmd or l2fwd) forwards packets back to A immediately (A->B->A),
and A receives packets and calculates time difference between current time
and the embedded time stamp. (code :
https://github.com/kay21s/dpdk/tree/master/examples/recv_send)

I have 3 machines, and performing the above experiment on each pair leads
to a similar latency. However, previous academic papers report that DPDK
offers only a few 10 microseconds round trip latency.

What's the round trip latency DPDK is supposed to offer? Have you measured
it at Intel?

Thanks a lot,
Kai