[Patch v2] net/netvsc: report correct stats values

[Ferruh Yigit]

On 5/3/2022 9:48 PM, Long Li wrote:
>> Subject: Re: [Patch v2] net/netvsc: report correct stats values
>>
>> On 5/3/2022 8:14 PM, Long Li wrote:
>>>> Subject: Re: [Patch v2] net/netvsc: report correct stats values
>>>>
>>>> On 5/3/2022 7:18 PM, Long Li wrote:
>>>>>> Subject: Re: [Patch v2] net/netvsc: report correct stats values
>>>>>>
>>>>>> On Tue, 26 Apr 2022 22:56:14 +0100
>>>>>> Ferruh Yigit <ferruh.yigit at xilinx.com> wrote:
>>>>>>
>>>>>>>>      		if (i < RTE_ETHDEV_QUEUE_STAT_CNTRS) {
>>>>>>>> -			stats->q_opackets[i] = txq->stats.packets;
>>>>>>>> -			stats->q_obytes[i] = txq->stats.bytes;
>>>>>>>> +			stats->q_opackets[i] += txq->stats.packets;
>>>>>>>> +			stats->q_obytes[i] += txq->stats.bytes;
>>>>>>>
>>>>>>> This is per queue stats, 'stats->q_opackets[i]', in next iteration
>>>>>>> of the loop, 'i' will be increased and 'txq' will be updated, so
>>>>>>> as far as I can see the above change has no affect.
>>>>>>
>>>>>> Agree, that is why it was just assignment originally.
>>>>>
>>>>> The condition here is a little different. NETVSC is a master device
>>>>> with
>>>> another PMD running as a slave. When reporting stats values, it needs
>>>> to add the values from the slave PMD. The original code just
>>>> overwrites the values from its slave PMD.
>>>>
>>>> Where the initial values are coming from, 'hn_vf_stats_get()'?
>>>>
>>>> If 'hn_vf_stats_get()' fills the stats, what are the values kept in 'txq-
>>> stats.*'
>>>> in above updated loop?
>>>
>>> Yes, hn_vf_stats_get() fills in the stats from the slave PMD. txq->stats
>> values are from the master PMD. Those values are different and accounted
>> separated from the values from the slave PMD.
>>
>> I see, since this is a little different than what most of the PMDs do, can you
>> please put a little more info to the commit log? Or perhaps can add some
>> comments to the code.
> 
> Ok, will do.
> 
>>
>> And still 'stats->rx_nombuf' change is not required right? If so can you
>> remove it in the next version?
> 
> It is still needed. NETVSC unconditionally calls the slave PMD to receive packets, even if it can't allocate a mbuf to receive a synthetic packet itself. The accounting of rx_nombuf is valid because the synthetic packets (to NETVSC) and VF packets (to slave PMD) are routed separately from Hyper-V.

I am not referring to the "+=" update, my comment was because 
'stats->rx_nombuf' is overwritten in 'rte_eth_stats_get()' [1].
Is it still required?

[1]
https://git.dpdk.org/dpdk/tree/lib/ethdev/rte_ethdev.c?h=v22.03#n2518