Hi Matheus,
On 7/28/23 16:12, Thomas Monjalon wrote:
Hello,
You can have packets distributed to multiple queues without RSS.
If you really wants to enable the RSS algorithms,
it seems not supported for now with vhost_user.
It can be enabled with vhost running in the kernel:
https://qemu.readthedocs.io/en/latest/devel/ebpf_rss.html
Thomas is right, DPDK Virtio PMD supports RSS, but DPDK Vhost-user does
not (yet).
However, as you seem to be using a fairly recent OVS-DPDK version, you
can enable Hash-based Tx packet steering mode on the vhostuser ports.
It has been introduced in OVS v2.17:
https://docs.openvswitch.org/en/latest/topics/userspace-tx-steering/
It is usefull if you have less PMD threads in OVS than the number of
queues in your Virtio device. Traffic will be distributed on the queues
based on the 5-tuple hash computed for OVS switching. The downside is
that this is not configurable as RSS though (Key not configurable, no
filters, ...).
Regards,
Maxime
26/07/2023 00:58, Matheus Stolet:
Hello,
I am trying to run a DPDK application with RSS enabled so that I can
have multiple rx queues. This application is running inside a VM. This
VM is hosted by QEMU using KVM acceleration and OvS with DPDK and
vhost-user are used in the backend. So to clarify things there are two
DPDK portions to this. The first is the DPDK portion used by OvS that
bypasses the host operating system. This is working fine. The other is a
DPDK application inside the virtual machine that will bypass the guest
operating system. This is where I am having trouble with.
When I set rte_eth_conf.rxmode.mq_mode = ETH_MQ_RX_RSS in my application
I get the following errors:
Warning: NIC does not support all requested RSS hash functions.
virtio_dev_configure(): RSS support requested but not supported by the
device
Port0 dev_configure = -95
I setup my VM in QEMU to have mq=on and queues=10. I also set the number
of rx_queues when creating the vhost port using ovs to 10. Before
binding the interface to DPDK, I used ethtool to verify if the network
interface was actually setup to have multiple queues.
Running the 'ethtool -l enps02' command yields the following output:
Pre-set maximums:
RX: 0
TX: 0
Other: 0
Combined: 10
Current hardware settings:
RX: 0
TX: 0
Other: 0
Combined: 10
From my understanding the combined values indicate that the interface
was properly setup to have multiple queues, so why am I getting the
unsupported RSS error? Are there other configuration steps that I have
to take to get this to work? Is RSS with DPDK not supported at all
inside a VM at the moment? Perhaps the "Port0 dev_configure() = -95"
error means something else? Without the receive side scaling turned on
my application is not able to achieve the desired throughput and won't
scale when I assign more cores to the application.
Versions:
VM
DPDK: 21.11.4
Kernel: 5.4.0-148-generic
Distribution: Ubuntu 20.04
Host
DPDK: 21.11.4
QEMU: 8.0.90
OvS: 3.0.5
Kernel: 5.15.111.1.amd64-smp
Distribution: Debian 11
