[ovs-discuss] Flow removed reporting statistics with value 0

[Ricardo Schmidt]

Hi all,

We are running OpenFlow 1.3, OVS 2.1.2, and Ryu. Switch and controller are
in the same machine with virtualized interfaces.

We are running some stress tests on OVS to check the accuracy of the
reported statistics from flow removed messages.

In a first test we inject an average of 100 simultaneous flows per sec in
the switch port, in the second an average of 250 flows/s and in the third
an average of 500 flows/s.

It seems that the more flows/s the more erratic the behavior of the
counters. The total sum of reported bytes and packets at the end (summing
all flow removed messages) is always less than the number of injected ones.
This problem increases with the increasing number of flows/s. We do make
sure that our flow mod always include the flag asking to the switch to send
the flow removed upon entry expiration.

In the third case, with 500 flows/s, not only the counters are off, but we
also surprisingly see many flow removed messages in which counters have
value of zero. That is, as if the total forwarded packets and bytes was
zero.

Does anyone has an idea of what might be happening?

Could this be a limitation of OVS in a virtualized setting? Although we
have seen reports of tests of OVS with many more simultaneous flows.

Thanks for your attention.

Cheers,
Ricardo
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