Re: [dpdk-dev] [PATCH] ethdev: fix statistics description

["Morten Brørup" <mb@smartsharesystems.com>]

> -----Original Message-----
> From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Dai, Wei
> Sent: Wednesday, November 2, 2016 9:29 AM
> To: Thomas Monjalon; Mcnamara, John; Ananyev, Konstantin; Wu, Jingjing;
> Zhang, Helin; Dai, Wei; Curran, Greg
> Cc: dev@dpdk.org
> Subject: Re: [dpdk-dev] [PATCH] ethdev: fix statistics description
> 
> Hi, John & Greg
> 
> Would you please give any opinion for this patch ?
> 
> I have looked through all PMDs and found not all statistics items can
> be supported by some NIC.
> For example,  rx_nombuf,  q_ipackets,  q_opackets,  q_ibytes and
> q_obytes are not supported by i40e.
> But when the function rte_eth_stats_get(uint8_t port_id, struct
> rte_eth_stats *stats) is called for i40e PMD, Above un-supported
> statistics item in output stats are zero, this is not real value.
> So far, there is no way to know whether an item in struct rte_eth_stats
> is supported or not only from this structure definition.
> Maybe some structure member can be added to indicate each of statistics
> item valid or not.
> But this means ABI change.
> 
> 
> > -----Original Message-----
> > From: Thomas Monjalon [mailto:thomas.monjalon@6wind.com]
> > Sent: Tuesday, October 4, 2016 5:35 PM
> > To: Dai, Wei <wei.dai@intel.com>; Mcnamara, John
> > <john.mcnamara@intel.com>
> > Cc: dev@dpdk.org
> > Subject: Re: [dpdk-dev] [PATCH] ethdev: fix statistics description
> >
> > 2016-08-26 18:08, Wei Dai:
> > >  /**
> > >   * A structure used to retrieve statistics for an Ethernet port.
> > > + * Not all statistics fields in struct rte_eth_stats are supported
> > > + * by any type of network interface card (NIC). If any statistics
> > > + * field is not supported, its value is 0 .
> > >   */
> > >  struct rte_eth_stats {
> >
> > I'm missing the point of this patch.
> > Why do you think it is a fix?
> >
> > John, any opinion?
> 

I think the source code comment is an improvement. I would also like to see a source code comment describing the criteria for choosing which counters go in the eth_stats, and which counters are relegated to the eth_xstats.

It doesn't look like the Interfaces MIB (IF-MIB) or even the etherStats MIB drives this selection.

The ifOutQLen in the IF-MIB is deprecated; I guess it is not important for network monitoring. But fast access to the queue lengths are obviously useful for a fast path application with RED or other intelligent queue overflow handling mechanisms, so in my mind they are useful here.

-Morten