[ovs-dev] [PATCH v18] Improved Packet Drop Statistics in OVS

Federico Iezzi fiezzi at redhat.com
Fri Jan 3 16:39:00 UTC 2020

> On 18 Dec 2019, at 3:20 pm, Ilya Maximets <i.maximets at ovn.org> wrote:
> On 18.12.2019 05:48, Anju Thomas wrote:
>> Currently OVS maintains explicit packet drop/error counters only on port
>> level.  Packets that are dropped as part of normal OpenFlow processing
>> are counted in flow stats of “drop” flows or as table misses in table
>> stats. These can only be interpreted by controllers that know the
>> semantics of the configured OpenFlow pipeline.  Without that knowledge,
>> it is impossible for an OVS user to obtain e.g. the total number of
>> packets dropped due to OpenFlow rules.
>> Furthermore, there are numerous other reasons for which packets can be
>> dropped by OVS slow path that are not related to the OpenFlow pipeline.
>> The generated datapath flow entries include a drop action to avoid
>> further expensive upcalls to the slow path, but subsequent packets
>> dropped by the datapath are not accounted anywhere.
>> Finally, the datapath itself drops packets in certain error situations.
>> Also, these drops are today not accounted for.This makes it difficult
>> for OVS users to monitor packet drop in an OVS instance and to alert a
>> management system in case of a unexpected increase of such drops.
>> AlsoOVS trouble-shooters face difficulties in analysing packet drops.
>> With this patch we implement following changes to address the issues
>> mentioned above.
>> 1. Identify and account all the silent packet drop scenarios
>> 2. Display these drops in ovs-appctl coverage/show
>> Co-authored-by: Rohith Basavaraja <rohith.basavaraja at gmail.com>
>> Co-authored-by: Keshav Gupta <keshugupta1 at gmail.com>
>> Signed-off-by: Anju Thomas <anju.thomas at ericsson.com>
>> Signed-off-by: Rohith Basavaraja <rohith.basavaraja at gmail.com>
>> Signed-off-by: Keshav Gupta <keshugupta1 at gmail.com>
>> Acked-by: Eelco Chaudron <echaudro at redhat.com
>> ---
> Thanks.  This version looks OK to me beside the fact that I'd rename
> the patch to something like "userspace: Improved packet drop statistics.",
> but this is minor.  One more thing is that we might want to rename
> 'enum xlate_error' to 'enum ovs_xlate_error' and prefix all its members
> with 'OVS_' to keep the style along with kernel definitions, but this is
> a mechanical change that could be done later in a separate patch as it
> will touch a lot of unrelated code.
> Acked-by: Ilya Maximets <i.maximets at ovn.org>
> Hi Ben,
> could you, please, take a look at this patch one more time?
> There were a couple of changes as we moved 'enum xlate_error' to
> openvswitch.h header to avoid inclusion of 'ofproto/ofproto-dpif-xlate.h'
> from the 'lib' code, new datapath capability was documented and we
> cleaned the patch up a little bit.

Any news? We’re finally this close for merging the patch set.

> BTW, I will be traveling starting from tomorrow until the end of next
> week, so feel free to apply this patch if it looks good to you.  I could
> apply it myself today (if you could reply on it today) or after my trip.
> Best regards, Ilya Maximets.
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