[ovs-discuss] Drops in OVS

Abhishek Verma abhishekv.verma at gmail.com
Sun Aug 2 02:19:56 UTC 2015


HI,

Is my understanding below correct?


On Fri, Jul 31, 2015 at 10:14 AM, Abhishek Verma <abhishekv.verma at gmail.com>
wrote:

> Hi Flavio,
>
>
>> > Is this correct?
>>
>> No, there is a cache in the kernel which is periodically refreshed or
>> empty at the initialization.  When the first packet comes in the
>> packet is queued to the userspace daemon which will update the
>> kernel's cache.  Next packets matching the cached flow will pass
>> directly.
>>
>
> Aha. So, the of-ctl add-flow really adds a flow only in the User Space and
> nothing in the kernel space. If this flow rule isnt added then all packets
> will hit the default rule where we do normal L2 learning and switching. By
> adding of-ctl add-flow rules we simply over-ride that behavior.
>
> The real flows that get added by the user space daemon that the packets
> actually hit can be viewed by "ovs-dpctl dump-flows".
>
> Is this how it is?
>
>
>> However, depending on how you programmed your flows and the traffic,
>> you could see a burst coming for a flow that isn't cached yet. Since
>> the queue is limited, it can overflow.
>>
>
> Ok, and these drops are visible when i give "ovs-dpctl show" command. Is
> there a way to increase this queue size?
>
> Flows afaik are always timed out after 5 secs. Assume i have an
> application that bursts every 6 secs. In that case i always run the risk of
> losing packets. Is there a way to pin a flow or increase its timeout value?
>
> Thanks, Abhishek
>
>
Thanks, Abhishek
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://openvswitch.org/pipermail/ovs-discuss/attachments/20150802/ce498102/attachment-0002.html>


More information about the discuss mailing list