Re: [dpdk-dev] [PATCHv2 0/5] ethdev: add new API to retrieve RX/TX queue information

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

Hi Mirek,

> -----Original Message-----
> From: Walukiewicz, Miroslaw
> Sent: Thursday, June 18, 2015 2:31 PM
> To: Ananyev, Konstantin; dev@dpdk.org
> Subject: RE: [dpdk-dev] [PATCHv2 0/5] ethdev: add new API to retrieve RX/TX queue information
> 
> Konstantin,
> 
> Is there a possibility to read information about available space in NIC queue for TX.

I suppose it is possible as some future addition.
As I said in the commit message, I left some reserved space, so extra fields could be added to the structure without ABI breakage.
For now, I just added some static/config information for the queue, but I think it is possible and plausible to have some runtime information too.

> 
> It is quite easy to compute (or even available directly)  and very useful especially for application sending multi-descriptor packets like
> TCP TSO.
> 
> Now there is no access to such information and the transmit packet function must be called to
> be sure that there is available space.

Hmm, as I said I was thinking about adding some RT information in future:
number of free descriptors (from SW point of view), index of next descriptor to process by SW, etc.
But my thought it would be use by some watchdog thread to collect statistics/detect stall, etc.
I didn't intend it to be used by IO thread. 

I am not sure why do you need to call such function at RT?
PMD wouldn't TX a packet, if there is not enough free TXDs for the whole packet.
>From other side upper layer, can't always calculate correctly how many TXD it would really need
(context descriptors might be needed, etc).
 Plus, even if nb_tx_free==X, in reality it could be there much more free TXDs, and SW just need
to process them (and would do that at next  tx_burst() call.
So, why just not:
...
n = tx_burst(..., nb_tx);
if (n < nb_tx) {requeue unsent of packets;}
?

Konstantin

> 
> Mirek
> 
> > -----Original Message-----
> > From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Konstantin Ananyev
> > Sent: Thursday, June 18, 2015 3:19 PM
> > To: dev@dpdk.org
> > Subject: [dpdk-dev] [PATCHv2 0/5] ethdev: add new API to retrieve RX/TX
> > queue information
> >
> > Add the ability for the upper layer to query RX/TX queue information.
> > Right now supported for:
> > ixgbe, i40e, e1000 PMDs.
> >
> > Konstantin Ananyev (5):
> >   ethdev: add new API to retrieve RX/TX queue information
> >   i40e: add support for eth_(rxq|txq)_info_get
> >   ixgbe: add support for eth_(rxq|txq)_info_get
> >   e1000: add support for eth_(rxq|txq)_info_get
> >   testpmd: add new command to display RX/TX queue information
> >
> >  app/test-pmd/cmdline.c           | 48 +++++++++++++++++++++++++
> >  app/test-pmd/config.c            | 67
> > ++++++++++++++++++++++++++++++++++
> >  app/test-pmd/testpmd.h           |  2 ++
> >  drivers/net/e1000/e1000_ethdev.h | 12 +++++++
> >  drivers/net/e1000/em_ethdev.c    |  2 ++
> >  drivers/net/e1000/em_rxtx.c      | 38 ++++++++++++++++++++
> >  drivers/net/e1000/igb_ethdev.c   |  4 +++
> >  drivers/net/e1000/igb_rxtx.c     | 36 +++++++++++++++++++
> >  drivers/net/i40e/i40e_ethdev.c   |  2 ++
> >  drivers/net/i40e/i40e_ethdev.h   |  5 +++
> >  drivers/net/i40e/i40e_rxtx.c     | 42 ++++++++++++++++++++++
> >  drivers/net/ixgbe/ixgbe_ethdev.c |  4 +++
> >  drivers/net/ixgbe/ixgbe_ethdev.h |  6 ++++
> >  drivers/net/ixgbe/ixgbe_rxtx.c   | 42 ++++++++++++++++++++++
> >  lib/librte_ether/rte_ethdev.c    | 54 ++++++++++++++++++++++++++++
> >  lib/librte_ether/rte_ethdev.h    | 77
> > +++++++++++++++++++++++++++++++++++++++-
> >  16 files changed, 440 insertions(+), 1 deletion(-)
> >
> > --
> > 1.8.5.3