Re: [dpdk-dev] [PATCHv4 1/5] ethdev: add new API to retrieve RX/TX queue information

["Ananyev, Konstantin" <konstantin.ananyev@intel.com>]

Hi Thomas,

> -----Original Message-----
> From: Thomas Monjalon [mailto:thomas.monjalon@6wind.com]
> Sent: Thursday, July 23, 2015 5:17 PM
> To: Ananyev, Konstantin
> Cc: dev@dpdk.org; Stephen Hemminger
> Subject: Re: [dpdk-dev] [PATCHv4 1/5] ethdev: add new API to retrieve RX/TX queue information
> 
> 2015-07-23 10:52, Ananyev, Konstantin:
> > From: Stephen Hemminger [mailto:stephen@networkplumber.org]
> > > Konstantin Ananyev <konstantin.ananyev@intel.com> wrote:
> > > > Add the ability for the upper layer to query RX/TX queue information.
> [...]
> > > Since all this data should be rxconf already, Is it possible
> > > to do a generic version of this and not have to change every driver.
> >
> > I don't think it is possible to implement these two functions at rte_etdev level only.
> > At least not with current ethdev/PMD implementation:
> > -  Inside struct rte_eth_dev_info we have only: 'struct rte_eth_rxconf default_rxconf;'.
> > We don't have rxconf here for each configured rx queue.
> > That information is maintained by PMD and inside PMD, different devices have different format for queue structure.
> > - rte_eth_rxq_info contains not only rxconf but some extra information: mempool in use by that queue,
> >  min/max possible number of descriptors.
> >  Also my intention was that in future that structure would be extended to provide some RT info about queue:
> >  (number of free/used descriptors from SW point of view, etc).
> 
> Isn't it what rte_eth_rx_queue_count() provides?

Not exactly.
rte_eth_rx_queue_count() actually scans HW descriptors to check their status.
I was thinking about returning just a snapshot of SW state: how many free/used RXDs are from PMD perspective
(just by collecting info from *_rx_queue structure, without reading actual HW registers/descriptors).
Anyway, right now it is not implemented - it is just a thought for future expansion.
Konstantin


> Maybe we should deprecate it in favor of rte_eth_rx_queue_info_get().