[ovs-dev] 64Byte packet performance regression on 2.9 from 2.7

Shahaji Bhosle shahaji.bhosle at broadcom.com
Fri Jun 15 02:15:27 UTC 2018

I just upgraded from OvS 2.7 + DPDK 16.11 to OvS2.9 + DPDK 17.11 and
running into performance issue with 64 Byte packet rate. One interesting
thing that I notice that even at very light load from IXIA the processing
cycles on all the PMD threads run close to 100% of the cpu cycle on 2.9
OvS, but on OvS 2.7 even under full load the processing cycles remain at
75% of the cpu cycles.

Attaching the FlameGraphs of both the versions, the only thing that pops
out to me is the new way invoking netdev_send() is on 2.9 is being invoked
via  dp_netdev_pmd_flush_output_packets() which seems to be adding another
~11% to the whole rx to tx path.

I also did try the tx-flush-interval to 50 and more it does seem to help,
but not significant enough to match the 2.7 performance.

Any help or ideas would be really great. Thanks, Shahaji

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