[ovs-discuss] Fwd: Packet drops with high rate of Packet_In

[Luiz Ozaki]

Have you tried without the controller ?

Maybe the controller is taking too long to install the flows.


On 11/21/13 1:57 PM, Anton Matsiuk wrote:
> I request log files up to debug level, namely:
> ovs-vswitchd.log
> ovs-dpctl.log
> ovs-ofctl.log
> but none of them shows any messages related to packet drops. All the 
> statistics shows that correct number of flows was installed and only 
> part of packets was processed.
> That's why I am asking, is there any else possibilities (beyond log 
> files) to track packet drops in input buffers and probably to fix 
> them? Or at least in which direction I should search for a solution?
>
> On 20 November 2013 18:13, Ben Pfaff <blp at nicira.com 
> <mailto:blp at nicira.com>> wrote:
>
>     On Wed, Nov 20, 2013 at 12:35:25PM +0100, Anton Matsiuk wrote:
>     > I test Open vSwitch in the following scheme: I use 2 hosts directly
>     > connected to OVS and external OpenFlow Controller. Host1
>     generates UDP
>     > datagrams with sequential ports towards Host2, Host 2 listens
>     for these UDP
>     > datagrams. In responce to every UDP datagram OVS generates
>     Packet_In and
>     > Controller sends Flow_Mod back with L4 granularity (so for every
>     pair of
>     > UDP port numbers it installs separate flow). I send bunch of UDP
>     datagrams
>     > from Host1 and calculate how many of them arrived to Host2. I
>     tried both
>     > with detached controller and running in the same machine as OVS.
>     I tested
>     > it on different machines (in Mininet and with separated real
>     hosts). I use
>     > out-of-band option for controller and disable-in-band=true.
>     >
>     >
>     > Starting  some number of packets ( around >300) packet drops are
>     observed.
>     > For instance, if I generate 500 UDP packets in 120 ms only
>     around 350 of
>     > them arrive to Host2 (Subsequent packets of the same flow can
>     arrive to
>     > Host2, but first packets of flows always experience drops)
>     >
>     >
>     > ovs-ofctl dump-aggregate show that all the flows are installed
>     but only
>     > part of packets are processed through them:
>     >
>     > NXST_AGGREGATE reply (xid=0x4): packet_count=356 byte_count=42364
>     > flow_count=500
>     >
>     >
>     > ovs-ofctl dump-ports also shows that 500 packets arrive on ingress
>     > interface and only 356 leave egress.
>     >
>     >
>     > ovs-dpctl show ?s shows the same ?  500 flows installed and 356
>     packets
>     > processed.
>     >
>     >
>     > Also I tried to replace Flow_Mods with Packet_Out messages for every
>     > packet, but I experienced the same drops. It seems like OVS
>     starts dropping
>     > packets after some threshold (or buffer overload).
>     >
>     >
>     > Is there any possibility to debug these drops and maybe to
>     manipulate
>     > ingress buffer sizes (or queue priorities) in order to avoid
>     such drops?
>
>     Yes, I think you will have to do the initial debugging yourself,
>     to find
>     out where the drop is occurring.  When you report that back to us, we
>     can help you figure out how to fix it.
>
>
>
>
> -- 
> Best regards,
> Anton Matsiuk
>
>
> _______________________________________________
> discuss mailing list
> discuss at openvswitch.org
> http://openvswitch.org/mailman/listinfo/discuss
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://openvswitch.org/pipermail/ovs-discuss/attachments/20131121/d59b13ec/attachment.html>