[dpdk-dev] Packet drops during non-exhaustive flood with OVS and 1.8.0

[Andrey Korolyov <andrey@xdel.ru>]

Hello,

I observed that the latest OVS with dpdk-1.8.0 and igb_uio starts to
drop packets earlier than a regular Linux ixgbe 10G interface, setup
follows:

receiver/forwarder:
- 8 core/2 head system with E5-2603v2, cores 1-3 are given to OVS exclusively
- n-dpdk-rxqs=6, rx scattering is not enabled
- x520 da
- 3.10/3.18 host kernel
- during 'legacy mode' testing, queue interrupts are scattered through all cores

sender:
- 16-core E52630, netmap framework for packet generation
- pkt-gen -f tx -i eth2 -s 10.6.9.0-10.6.9.255 -d
10.6.10.0-10.6.10.255 -S 90:e2:ba:84:19:a0 -D 90:e2:ba:85:06:07 -R
11000000, results in 11Mpps 60-byte packet flood, there are constant
values during test.

OVS contains only single drop rule at the moment:
ovs-ofctl add-flow br0 in_port=1,actions=DROP

Packet generator was launched for tens of seconds for both Linux stack
and OVS+DPDK cases, resulting in zero drop/error count on the
interface in first, along with same counter values on pktgen and host
interface stat (means that the none of generated packets are
unaccounted).

I selected rate for about 11M because OVS starts to do packet drop
around this value, after same short test interface stat shows
following:

statistics          : {collisions=0, rx_bytes=22003928768,
rx_crc_err=0, rx_dropped=0, rx_errors=10694693, rx_frame_err=0,
rx_over_err=0, rx_packets=343811387, tx_bytes=0, tx_dropped=0,
tx_errors=0, tx_packets=0}

pktgen side:
Sent 354506080 packets, 60 bytes each, in 32.23 seconds.
Speed: 11.00 Mpps Bandwidth: 5.28 Gbps (raw 7.39 Gbps)

If rate will be increased up to 13-14Mpps, the relative error/overall
ratio will rise up to a one third. So far OVS on dpdk shows perfect
results and I do not want to reject this solution due to exhaustive
behavior like described one, so I`m open for any suggestions to
improve the situation (except using 1.7 branch :) ).