[ovs-discuss] Warning logs flooding: failed to flow_del (No such file or directory)

[Alex Wang]

Hey Andrey,

Thanks for reporting the issue,  Please see my reply below,

Hello,
>
> getting the lookalike message on 2.1.3 where the problem described in
> the conversation should not take a place:
>

Yes, v2.1.3 contains the fix commit 3601bd879 (datapath: Use exact lookup
for flow_get and flow_del.)





> 2014-10-03T17:24:30.429Z|00026|dpif(revalidator_11)|WARN|system at ovs-system
> :
> failed to flow_del (No such file or directory)
>
> skb_priority(0),in_port(2),skb_mark(0),eth(src=xx:xx:xx:xx:xx:xx,dst=yy:yy:yy:yy:yy:yy),eth_type(0x0800),ipv4(src=zz.zz.zz.zz,dst=ii.jj.kk.ll,proto=6,tos=0,ttl=118,frag=no),tcp(src=nnn,dst=mmm),tcp_flags(0x018)
>


Could you help confirm the following things?

1. if the code you use contains commit 3601bd879

2. for the flows in 'failed to flow_del' logs, were they the same flow or
same set of flows?  or totally random flows?

One thing comes to my mind is that, for v2.1.3, the same dp flow could
actually be dumped more than once.  since the flow dumping happens in
batch, so for example assume the current batch dumped flow A, then the flow
adds before the next dump move back the position of flow A in the link
list, then the next dump will dump flow A again.

So, the revalidator will process flow A twice.  And if the first process
decides to delete flow A.  The next process will do the same thing but
result in this 'failed to flow_del' error~


3. don't know if it is possible for your to provide the result of following
commands:

ovs-dpctl dump-flows | sed -n 's/^.*\(used:[0-9.]\+\).*$/\1/p'





>
> Preconditions are following:
>   - 30k installed non-overlapping ip mask flows, ttl=4h,
>   - 3k dp flows,
>   - moderate traffic, on about 200mbit and hitting 2000prefixes/s.

The error appears long before flow` expiration time, so I think that
> there is something wrong. Also even with very low flow_add ratio (~
> 5/s) I am getting moderately high cpu consumption by vswitchd with
> such a setup, on about 50% of single Xeon core, comparing to 20% for
> proactive-only match for same traffic with small number of installed
> rules (~100).
>


For 'flow_add', do you mean OpenFlow flows?  If so, i could more time to
add/del flows in classifier,

Do you have more interfaces as compared to the other setup you mentioned?
With more interfaces, it would take more time to update stats/status.

Thanks,
Alex Wang,
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