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

[Long Li <longli@microsoft.com>]

> 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.

> 
> [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