[dpdk-users] High Packet missed rate

[Mohammad Malihi]

Hi
I'm new on dpdk and i have problems about high packet dropping ratio
when using pktgen and l2fwd in rates greter than 1.5 Gbs (using pktgen).
In order to have benchmarks on dpdk forwarding capabilities in 10 Gbs rate,
i've established a very simple test environment as depicted bellow :

---------------------------------
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|Server 1 port 0 (Intel 82599ES)| -----> |Server 2 port 0 (Intel 82599ES)|
---------------------------------
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                                                                          |
                                                             (bridge via
l2fwd app)
                                                                          |
----------------------------------------------
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|Server 1 port 1 (Intel 82599ES)| <-----  |Server 2 port 1 (Intel 82599ES)|
---------------------------------------------
----------------------------------------------

Sending packets (on server 1) with size 64 bytes at rate 10 Gbs can be done
by running pktgen with the following parameters :
   -c 0x07 -n 12 -- -P -m "1.0, 2.1"
and following commands in interactive mode :
    set 0 rate 100
    set 0 size 64
    start 0

At the other side (server 2), l2fwd app forwards packets with parameters :
   -c 0x07 -n 12 -- -p 0x03 -q 1 -T 10
(core 0 receives packets from port 0 and core 1 sends them using port 1)

Hardware Specifications (same for 2 servers) :
    Processors : 2 "Intel Xeon 2690 v2" (each of them has 20 cores).
    NIC : "Intel 82599ES 10-GB" with 2 interfaces (connected to x8 PCIe Gen
2 -> 5 GT/s)
    Memory : 264115028 KB

Also hugepage sizes on each side are totally 128 GB (64 GB(huge page->1GB)
for each node)
and all ports and used cores(0,1) are on the same NUMA node.

I've made some modifcations to l2fwd app to show packet dropping count by
calling
"rte_eth_stats_get" in "print_stats" function and using "imissed" member of
"rte_eth_stas".

The results on screen show that in rates greater than 1.5 Gbs, packet
dropping (by hardware) occures.
I wonder, why there is packet missing in rates bellow 10 Gbs

Thanks in advance