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?
