On 08/11/2017 09:27 AM, Jan Scheurich wrote: > Hi Ilya, > > Tuning the per EMC insertion probability per port based on detailed knowledge > about the nature of traffic patterns seems a micro-optimization to me, which > might be helpful in very controlled setups e.g. in synthetic benchmarks, but > very hard to apply in more general use cases, such as vSwitch in OpenStack, > where the entity (Nova compute) configuring the vhostuser VM ports has no > knowledge at all about traffic characteristics. > > The nice property of the probabilistic EMC insertion is that flows with more > traffic have a higher chance of ending up in the EMC than flows with lower > traffic. In your case the few big encapsulated flows from the VM should have > a higher chance to make it into the EMC than the many smaller individual > flows into the VM and thus automatically get the bulk of EMC hits. > > Do you have empirical data that shows that this effect is not sufficient and > performance can be significantly improved by per-port probabilities? > > In any case I would request to keep the global configuration option and only > add the per-port option to override the global probability if wanted. >
+1 for backwards compatibility by keeping the global config. > Thanks, Jan > >> > -----Original Message----- >> > From: [email protected] >> > [mailto:[email protected]] On Behalf Of Ilya Maximets >> > Sent: Thursday, 10 August, 2017 18:55 >> > To: [email protected] >> > Cc: Ilya Maximets <[email protected]>; Heetae Ahn >> > <[email protected]> >> > Subject: [ovs-dev] [PATCH 2/2] dpif-netdev: Per-port conditional EMC >> > insert. >> > >> > Conditional EMC insert helps a lot in scenarios with high numbers >> > of parallel flows, but in current implementation this option affects >> > all the threads and ports at once. There are scenarios there we have >> > different number of flows on different ports. For example, if one >> > of the VMs encapsulates traffic using additional headers, it will >> > recieve large number of flows but only few flows will come out of >> > this VM. In this scenario it's much faster to use EMC instead of >> > classifier for traffic from the VM, but it's better to disable EMC >> > for the traffic which flows to VM. >> > >> > To handle above issue 'emc-insert-inv-prob' was converted to per-port >> > option. Default value and behaviour kept as is. >> > >> > For example, following command sets the insertion probability for >> > packets that came from port 'dpdk0' to ~1/20, i.e. ~5%: >> > >> > ovs-vsctl set interface dpdk0 other_config:emc-insert-inv-prob=20 >> > >> > Signed-off-by: Ilya Maximets <[email protected]> >> > --- >> > Documentation/howto/dpdk.rst | 4 +- >> > NEWS | 2 +- >> > lib/dpif-netdev.c | 106 >> > +++++++++++++++++++++++++++++-------------- >> > tests/pmd.at | 7 ++- >> > vswitchd/vswitch.xml | 42 ++++++++++------- >> > 5 files changed, 106 insertions(+), 55 deletions(-) _______________________________________________ dev mailing list [email protected] https://mail.openvswitch.org/mailman/listinfo/ovs-dev
