[dpdk-users] high jitter in dpdk kni

Freynet, Marc (Nokia - FR) marc.freynet at nokia.com
Mon Jan 25 09:29:42 CET 2016


Some months ago we had a problem with the KNI driver.
Our DPDK application forwards to the Linux kernel through KNI the SCTP PDU received from the Eth NIC.
In one configuration, the SCTP port Source and Destination were constant on all SCTP connections.
This is a known SCTP issue as in the multi processor environment, the SCTP stack uses the port Source and Destination to hash the processor that will run the SCTP context in the kernel.
SCTP cannot use the IP address as a hash key thanks to the SCTP multi homing feature.

As all SCTP PDU on all SCTP connections where processed by the same Core, this creates a bottle neck and the KNI interface starts creating Jitter and even was losing PDU when sending the SCTP PDU to the IP Linux kernel stack.

I am wondering if in a previous release it you not be possible to add KNI a kind of load sharing with different queues on different cores to forward the received PDU to the IP Linux stack.

​"Bowl of rice will raise a benefactor, a bucket of rice will raise a enemy.", Chinese proverb.

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marc.freynet at nokia.com

-----Original Message-----
From: users [mailto:users-bounces at dpdk.org] On Behalf Of EXT Masoud Moshref Javadi
Sent: samedi 23 janvier 2016 15:18
To: users at dpdk.org
Subject: [dpdk-users] high jitter in dpdk kni

I see jitter in KNI RTT. I have two servers. I run kni sample application on one, configure its IP and ping an external interface.

sudo -E build/kni -c 0xaaaa -n 4 -- -p 0x1 -P --config="(0,3,5)"
sudo ifconfig vEth0

This is the ping result:
64 bytes from icmp_seq=5 ttl=64 time=1.93 ms
64 bytes from icmp_seq=6 ttl=64 time=0.907 ms
64 bytes from icmp_seq=7 ttl=64 time=3.15 ms
64 bytes from icmp_seq=8 ttl=64 time=1.96 ms
64 bytes from icmp_seq=9 ttl=64 time=3.95 ms
64 bytes from icmp_seq=10 ttl=64 time=2.90 ms
64 bytes from icmp_seq=11 ttl=64 time=0.933 ms

The ping delay between two servers without kni is 0.170ms.
I'm using dpdk 2.2.

Any thought on how to keep KNI delay predictable?


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