[dpdk-users] DPDK weird forwarding loss

[Kyle Larose]

Hi Jack,

On Mon, Nov 30, 2015 at 8:42 PM, Zhihan Jiang <jackcharm233 at gmail.com> wrote:
> Hello,
>

> Other settings: intel_iommu=on iommu=pt / blacklist ixgbevf on the host
> machine / pause frame off / pin all the ports to the same NUMA node &
> socket / VM uses CPU on the same NUMA node & socket.
>

> but there is always ~0.5%- 1% packet loss
>
> The command line for l3fwd is:
> ./build/l3fwd -c6 -n4 -w [whitelist devices] --socket-mem=1024,0 -- -p3
> --config "(0,0,1), (1,0,2)"
>


Try isolating the CPUs on your guest and host so that the forwarding
application cannot be preempted by something else.

See the 'isolcpus' kernel boot parameter.

http://www.linuxtopia.org/online_books/linux_kernel/kernel_configuration/re46.html

In my experience, drops that happen at low rates are caused by the
polling thread not being scheduled to receive packets often enough.
This can either be because it was preempted, which isolcpus will fix,
or because it is sleeping. IIRC l3fwd doesn't sleep, which leaves the
first case the only possibility.

Hope that helps,

Kyle