On Thu, 2 Mar 2017 18:05:52 +0300, Andrew Rybchenko <arybche...@solarflare.com> wrote: > On 03/02/2017 05:54 PM, Olivier Matz wrote: > >>>>> + * > >>>>> + * @param port_id > >>>>> + * The port identifier of the Ethernet device. > >>>>> + * @param queue_id > >>>>> + * The Rx queue identifier on this port. > >>>>> + * @param offset > >>>>> + * The offset of the descriptor starting from tail (0 is the next > >>>>> + * packet to be received by the driver). > >>>>> + * @return > >>>>> + * - (RTE_ETH_DESC_AVAIL): Descriptor is available for the hardware to > >>>>> + * receive a packet. > >>>>> + * - (RTE_ETH_DESC_DONE): Descriptor is done, it is filled by hw, but > >>>>> + * not yet processed by the driver (i.e. in the receive queue). > >>>>> + * - (RTE_ETH_DESC_USED): Descriptor is unavailable (hold by driver, > >>>>> + * not yet returned to hw). > >>>> It looks like it is the most suitable for descriptors which are reserved > >>>> and never used. > >>> Can you give some more details about what is a reserved but never > >>> used descriptor? (same question for Tx) > >> Our HW has a requirement to keep few descriptors always unused (i.e. > >> some gap between tail and head). It is just a few descriptors, but > >> invalid descriptor status may misguide application. E.g. if Rx queue > >> size is 512 and offset 510, it will always be unused (since it is > >> reserved). It is not an indication that core is too slow and can't keep > >> the pace. > > Understood. > > > > I can change _USED into _UNAVAIL (add it for Tx), with the following > > description: > > > > - (RTE_ETH_DESC_UNAVAIL): Descriptor is unavailable: either hold by driver > > and not yet returned to hw, or reserved by the hardware. > > Looks good. Do I understand correctly that it will be reported for > descriptors which are not refilled (posted to HW) because of rx_free_thresh? >
Yes
