[ovs-dev] [PATCH v10 2/5] dpif-netdev: Count cycles on per-rxq basis.

[Ilya Maximets]

On 15.01.2018 12:27, Stokes, Ian wrote:
>>>>>> +    /* Update send cycles for all the rx queues evenly. */
>>>>>
>>>>> Just a query, is it right that this is distributed evenly?
>>>>> If there are more packets from one rx queue than another will it
>>>>> make a difference or will the cycles spent sending that batch be
>>>>> the
>>> same as a batch of a small or larger size?
>>>>>
>>>>
>>>> Maybe the "evenly" comment is a misleading? The send cycles for each
>>>> rxq is updated proportionally for how many packets that rxq had in
>>>> the batch. I think this is about the best that can be done.
>>>>
>>>
>>> Yes, it means what Kevin said.
>>> I'm not sure about this comment. Should I change it?
>>> I'm also not sure if we need to describe distribution algorithm in
>> comments.
>>> It's quiet obvious for me, but I, as an author, can not be objective.
>>>
>>> How about something neutral like:
>>> /* Distribute the send cycles between the rx queues. */ ?
>>
>> How about this:
>> /* Distribute send cycles evenly among transmitted packets and assign to
>> their respective rx queues. */
>>
> 
> I think above looks ok to me, I won't block on this at this stage.
> 

OK. I've sent v11 with changed comment.

> Thanks
> Ian
> 
>> This approximation is actually not too bad as all packets in the batch
>> went to the same tx queue. The only error we make is to ignore the size of
>> the packets (which may still be substantial, though, given that the packet
>> copying cost for large packets is significant in real-world scenarios with
>> lots of L3 cache misses and especially across the QPI bus).
>>
>> BR, Jan