[ovs-git] [openvswitch/ovs] 4c30b2: dpif-netdev: Conditional EMC insert

[GitHub]

  Branch: refs/heads/master
  Home:   https://github.com/openvswitch/ovs
  Commit: 4c30b24602c3ab73447073f7bb7644647734a6c0
      https://github.com/openvswitch/ovs/commit/4c30b24602c3ab73447073f7bb7644647734a6c0
  Author: Ciara Loftus <ciara.loftus at intel.com>
  Date:   2017-02-16 (Thu, 16 Feb 2017)

  Changed paths:
    M AUTHORS.rst
    M Documentation/howto/dpdk.rst
    M NEWS
    M lib/dpif-netdev.c
    M tests/pmd.at
    M vswitchd/vswitch.xml

  Log Message:
  -----------
  dpif-netdev: Conditional EMC insert

Unconditional insertion of EMC entries results in EMC thrashing at high
numbers of parallel flows. When this occurs, the performance of the EMC
often falls below that of the dpcls classifier, rendering the EMC
practically useless.

Instead of unconditionally inserting entries into the EMC when a miss
occurs, use a 1% probability of insertion. This ensures that the most
frequent flows have the highest chance of creating an entry in the EMC,
and the probability of thrashing the EMC is also greatly reduced.

The probability of insertion is configurable, via the
other_config:emc-insert-inv-prob option. This value sets the average
probability of insertion to 1/emc-insert-inv-prob.

For example the following command changes the insertion probability to
(on average) 1 in every 20 packets ie. 1/20 ie. 5%.

ovs-vsctl set Open_vSwitch . other_config:emc-insert-inv-prob=20

Signed-off-by: Ciara Loftus <ciara.loftus at intel.com>
Signed-off-by: Georg Schmuecking <georg.schmuecking at ericsson.com>
Co-authored-by: Georg Schmuecking <georg.schmuecking at ericsson.com>
Acked-by: Kevin Traynor <ktraynor at redhat.com>
Signed-off-by: Daniele Di Proietto <diproiettod at vmware.com>