[dpdk-users] high jitter in dpdk kni

Masoud Moshref Javadi masood.moshref.j at gmail.com
Mon Jan 25 14:15:24 CET 2016

I see. But this should not be the issue in Ping.
By the way, I checked the timestamps of sending and receiving times at the
kni sample application (kni_ingress and kni_egress methods). The RTT at
that level is OK (0.1ms) and it seems the jitter comes from the kni kernel

On Mon, Jan 25, 2016 at 12:29 AM Freynet, Marc (Nokia - FR) <
marc.freynet at nokia.com> wrote:

> Hi,
> 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.
> Alcatel-Lucent France
> Centre de Villarceaux
> Route de Villejust
> 91620 NOZAY France
> Tel:  +33 (0)1 6040 1960
> Intranet: 2103 1960
> 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
> ping
> 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?
> Thanks

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