On Thu, Aug 29, 2019 at 11:40 AM Numan Siddique <nusid...@redhat.com> wrote: > > Hello Everyone, > > In one of the OVN deployments, we are seeing 100% CPU usage by ovn-controllers all the time. > > After investigations we found the below > > - ovn-controller is taking more than 20 seconds to complete full loop (mainly in lflow_run() function) > > - The physical switch is sending GARPs periodically every 10 seconds. > > - There is ovn-bridge-mappings configured and these GARP packets reaches br-int via the patch port. > > - We have a flow in router pipeline which applies the action - put_arp > if it is arp packet. > > - ovn-controller pinctrl thread receives these garps, stores the learnt mac-ips in the 'put_mac_bindings' hmap and notifies the ovn-controller main thread by incrementing the seq no. > > - In the ovn-controller main thread, after lflow_run() finishes, pinctrl_wait() is called. This function calls - poll_immediate_wake() as 'put_mac_bindings' hmap is not empty. > > - This causes the ovn-controller poll_block() to not sleep at all and this repeats all the time resulting in 100% cpu usage. > > The deployment has OVS/OVN 2.9. We have back ported the pinctrl_thread patch. > > Some time back I had reported an issue about lflow_run() taking lot of time - https://mail.openvswitch.org/pipermail/ovs-dev/2019-July/360414.html > > I think we need to improve the logical processing sooner or later. > > But to fix this issue urgently, we are thinking of the below approach. > > - pinctrl_thread will locally cache the mac_binding entries (just like it caches the dns entries). (Please note pinctrl_thread can not access the SB DB IDL). > > - Upon receiving any arp packet (via the put_arp action), pinctrl_thread will check the local mac_binding cache and will only wake up the main ovn-controller thread only if the mac_binding update is required. > > This approach will solve the issue since the MAC sent by the physical switches will not change. So there is no need to wake up ovn-controller main thread. > > In the present master/2.12 these GARPs will not cause this 100% cpu loop issue because incremental processing will not recompute flows. > > Even though the above approach is not really required for master/2.12, I think it is still Ok to have this as there is no harm. > > I would like to know your comments and any concerns if any. > > Thanks > Numan >
Hi Numan, I think this approach should work. Just to make sure, to update the cache efficiently (to avoid another kind of recompute), it should use ovsdb change-tracking to update it incrementally. Regarding master/2.12, it is not harmful except that it will add some more code and increase memory footprint. For our current use cases, there can be easily 10,000s mac_bindings, but it may still be ok because each entry is very small. However, is there any benefit for doing this in master/2.12? Thanks, Han _______________________________________________ dev mailing list d...@openvswitch.org https://mail.openvswitch.org/mailman/listinfo/ovs-dev