On 3/21/22 16:03, Amber, Kumar wrote:
> Hi Ilya,
> 
> Thanks for the comments.
> Replies are inline.
> 
>> -----Original Message-----
>> From: Ilya Maximets <[email protected]>
>> Sent: Thursday, March 17, 2022 5:30 PM
>> To: Amber, Kumar <[email protected]>; [email protected];
>> Stokes, Ian <[email protected]>
>> Cc: [email protected]; [email protected]; Eelco Chaudron
>> <[email protected]>; Ferriter, Cian <[email protected]>
>> Subject: Re: [ovs-dev] [PATCH v5] dpcls: Change info-get function to fetch
>> dpcls usage stats.
>>
>> On 12/15/21 05:15, Kumar Amber wrote:
>>> Modified the dplcs info-get command output to include the count for
>>> different dpcls implementations.
>>>
>>> $ovs-appctl dpif-netdev/subtable-lookup-prio-get
>>>
>>> Available dpcls implementations:
>>>   autovalidator (Use count: 1, Priority: 5)
>>>   generic (Use count: 0, Priority: 1)
>>>   avx512_gather (Use count: 0, Priority: 3)
>>>
>>
>> Hi, folks.
>>
>> Sorry for jumping in so late again, but Mike's recent patch gave me
>> flashbacks of the following discussion of a very similar functionality:
>>   https://patchwork.ozlabs.org/project/openvswitch/patch/1576855703-
>> [email protected]/
>>
>> We wanted to see which miniflow bits are in each subtable, so we ended up
>> reporting this information alongside the datapath flow information in the
>> output of dpctl/dump-flows via dp_extra_info.
>>
>> This new patch is intended to show which subtable lookup implementation is
>> used.  But this depends only on the miniflow bits and the current priorities.
>> And doesn't change in runtime (unless priorities changed manually).  What
>> I'm saying is that it's extremely similar information to what we're already
>> printing as part of dp_extra_info.
>>
>> Maybe instead of introducing extra counters, we could just add lookup
>> implementation to the extra info?
>>
>> Something like this:
>>
>>
>> recirc_id(0),in_port(1),packet_type(ns=0,id=0),eth_type(0x0800),ipv4(frag=n
>> o), \
>>     dp-extra-info:miniflow_bits(5,1),lookup(avx512_gather) \
>>     actions:hash(sym_l4(0)),recirc(0x1)
>>
>> I think, this format gives all the same information, because flows are dumped
>> per-PMD, so can be counted if needed (I'm not sure though how the value of
>> the counter is actually useful beside being zero or non-zero).
>> But also we have a visual representation of the actual flow and we can see
>> which lookup method is used for it.
>>
>> Implementation should also be simpler, because the infrastructure is already
>> in place.  'dp_extra_info' pointer can be protected by rcu to avoid race
>> conditions while re-generating the string on re-probe.
>> dpcls_subtable_get_best_impl() can be extended to return a name as a
>> constant string via the 'out' argument.
>>
>> Thoughts?
>>
> 
> I have already made a POC based on the Discussion above and will put that 
> patch in few days with the 
> 'dp_extra_info' showing DPCLS as well.
>  As for this Patch is also important as currently the get-command doesn’t 
> show much info and hence this improvement will make things clear for the user 
> through the dpcl-get-command.
> Hence request this usability feature to be merged.
> I will follow this patch with the 'dp_extra_info' showing DPCLS functions 
> next to give absolute clarity to the user.

Why the 'subtable-lookup-prio-get' should return anything except
for the priority of subtable lookup implementations?

That doesn't seem straightforward.  Especially if we'll have that
information reported in a different place already without need for
extra infrastructure.

> 
> Regards
> Amber
>> Best regards, Ilya Maximets.

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