Re: [PATCH] doc: update TAP device features

[Stephen Hemminger <stephen@networkplumber.org>]

On Fri, 4 Oct 2024 08:54:43 +0100
Bruce Richardson <bruce.richardson@intel.com> wrote:

> On Fri, Oct 04, 2024 at 05:09:21AM +0100, Ferruh Yigit wrote:
> > On 10/4/2024 3:26 AM, Stephen Hemminger wrote:  
> > > On Fri, 4 Oct 2024 02:48:21 +0100
> > > Ferruh Yigit <ferruh.yigit@amd.com> wrote:
> > >   
> > >> On 9/4/2024 4:42 PM, Stephen Hemminger wrote:  
> > >>> The TAP device does have per-queue stats and handles multi-process.
> > >>>
> > >>> Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
> > >>> ---
> > >>>  doc/guides/nics/features/tap.ini | 2 ++
> > >>>  1 file changed, 2 insertions(+)
> > >>>
> > >>> diff --git a/doc/guides/nics/features/tap.ini b/doc/guides/nics/features/tap.ini
> > >>> index f26355e57f..f2ea5cd833 100644
> > >>> --- a/doc/guides/nics/features/tap.ini
> > >>> +++ b/doc/guides/nics/features/tap.ini
> > >>> @@ -14,10 +14,12 @@ Basic stats          = Y
> > >>>  L3 checksum offload  = Y
> > >>>  L4 checksum offload  = Y
> > >>>  MTU update           = Y
> > >>> +Multiprocess aware   = Y
> > >>>    
> > >>
> > >> ack
> > >>  
> > >>>  Multicast MAC filter = Y
> > >>>  Unicast MAC filter   = Y
> > >>>  Packet type parsing  = Y
> > >>>  Flow control         = Y
> > >>> +Stats per queue      = Y
> > >>>    
> > >>
> > >> This feature name is misleading,
> > >> it is for 'rte_eth_dev_set_[rt]x_queue_stats_mapping()' API, which is
> > >> indeed for covering limitation for some drivers.
> > >> Tap does support getting stats per queue, but doesn't support above
> > >> documented feature.  
> > > 
> > > The stats queue mapping was a feature that was hinted at being removed.
> > > It only exists because of HW limitations on Intel ixgbe NIC and SW
> > > limitations from RTE_ETHDEV_QUEUE_STAT_CNTRS.
> > >   
> > 
> > 
> > We have a plan to remove 'RTE_ETHDEV_QUEUE_STAT_CNTRS', by moving queue
> > stats to xstats.
> > 
> > But ixgbe limitation is there.
> >   
> > > Perhaps there should be a generic SW emulation for this the mapping?
> > >  
> > 
> > Ack, cc'ed Bruce.
> > But I am not sure ROI of the effort at this stage.  
> 
> Not sure what the specific ask for me is here. :-) Overall, I think moving
> queue stats to xstats is the best way to go.
> 
> /Bruce

The problem is that xstats are free form, so it is not possible for application
to use them in device independent manner.