Re: Poor performance of ingress filter for separate VMs

Linux Advanced Routing and Traffic Control

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Neil Aggarwal wrote:
Hello everyone:

I have a CentOS server running two virtual machines using KVM.
Each machine has its own virtual device since I am using bridged
networking.

I am trying to allocate bandwidth to each virtual machine using tc.

I have these rules set up:

/sbin/tc qdisc add dev v1262 ingress handle ffff:
/sbin/tc filter add dev v1262 parent ffff: protocol ip prio 50 u32 match ip
src 0.0.0.0/0 police rate 5mbit burst 500k mtu 3100 drop flowid :1

/sbin/tc qdisc add dev v1263 ingress handle ffff:
/sbin/tc filter add dev v1263 parent ffff: protocol ip prio 50 u32 match ip
src 0.0.0.0/0 police rate 5mbit burst 500k mtu 3100 drop flowid :1

You can see them when I do a qdisc ls:

qdisc ingress ffff: dev v1262 parent ffff:fff1 ----------------
qdisc ingress ffff: dev v1263 parent ffff:fff1 ----------------

The problem is when v1262 is doing a large upload, v1263 gets starved.
If I remove the ingress qdisc, v1263 runs at full speed regardless of what
v1262 is doing.
Its as if the two devices are using the same queue.  I did not think that
would happen since
they are totally separate devices.

Any ideas what is happening here?

I've never tested with a virtual machine so don't know.

I have suggested mtu 3100 in the past as it happened to work on a quick test on a real 100m nic - maybe for vm you need to go higher, or just turn off any sort of offload for the virtual device with ethtool and see if that helps.

ethtool -k <devname>

to see what the settings are and eg.

ethtool -K <devname> gro off



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