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

[Ferruh Yigit <ferruh.yigit@xilinx.com>]

On 5/4/2022 7:38 PM, Long Li wrote:
>> Subject: Re: [Patch v2] net/netvsc: report correct stats values
>>
>> 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@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?
> 
> Yes, it is still needed. NETVSC calls the rte_eth_stats_get() on its slave PMD first, and stats->rx_nombuf is updated (overwritten) for its slave PMD. Afte that, it needs to add to its own dev->data->rx_mbuf_alloc_failed back to stats->rx_nombuf.
> 

But its own stat also will be overwritten (not in PMD function, but in 
ethdev layer).
'stats->rx_nombuf' assignment in the PMD seems has no effect and can be 
removed.

I can't see how it is needed, can you please put a call stack to describe?

>>
>> [1]
>> https://nam06.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgit.dpdk
>> .org%2Fdpdk%2Ftree%2Flib%2Fethdev%2Frte_ethdev.c%3Fh%3Dv22.03%23n25
>> 18&amp;data=05%7C01%7Clongli%40microsoft.com%7Cea473df2344c460d575
>> d08da2dca3e53%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C63787
>> 2643902917430%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQ
>> IjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&amp;sd
>> ata=FZO%2B%2BnWtLGstHHIZ2aXsDUKNI%2Fi9tbj6jONhp174qKw%3D&amp;res
>> erved=0