Re: [PATCH v1] ixgbe: remove vector pmd burst size restriction

Hi, 

[...]

quoted

diff --git a/drivers/net/ixgbe/ixgbe_rxtx.c b/drivers/net/ixgbe/ixgbe_rxtx.c
index 3f808b3..dbdb761 100644
--- a/drivers/net/ixgbe/ixgbe_rxtx.c
+++ b/drivers/net/ixgbe/ixgbe_rxtx.c

@@ -4008,7 +4008,8 @@ ixgbe_set_rx_function(struct rte_eth_dev *dev)
  	 */
  	} else if (adapter->rx_vec_allowed) {
  		PMD_INIT_LOG(DEBUG, "Vector rx enabled, please make sure

RX "

quoted

-				   "burst size no less than 32.");
+				    "burst size no less than 4 (port=%d).",
+			     dev->data->port_id);

I think it would be better to use RTE_IXGBE_DESCS_PER_LOOP instead of a
constant 4.

quoted

[...]

quoted

  /*
- * vPMD receive routine, now only accept (nb_pkts ==

RTE_IXGBE_VPMD_RX_BURST)

quoted

- * in one loop
+ * vPMD raw receive routine

I would keep some warning there, like "(if nb_pkts <
RTE_IXGBE_DESCS_PER_LOOP, won't receive anything)"

quoted

   *
   * Notice:
- * - nb_pkts < RTE_IXGBE_VPMD_RX_BURST, just return no packet
- * - nb_pkts > RTE_IXGBE_VPMD_RX_BURST, only scan

RTE_IXGBE_VPMD_RX_BURST

quoted

- *   numbers of DD bit
+ * - floor align nb_pkts to a RTE_IXGBE_DESC_PER_LOOP power-of-two
+ * - 'nb_pkts < 4' causes 0 packet receiving

Again, RTE_IXGBE_DESCS_PER_LOOP would be better than 4

[...]

quoted

  uint16_t
  ixgbe_recv_scattered_pkts_vec(void *rx_queue, struct rte_mbuf **rx_pkts,
  		uint16_t nb_pkts)
  {
  	struct ixgbe_rx_queue *rxq = rx_queue;
-	uint8_t split_flags[RTE_IXGBE_VPMD_RX_BURST] = {0};
+	uint8_t split_flags[nb_pkts];
+
+	memset(split_flags, 0, nb_pkts);

  	/* get some new buffers */
  	uint16_t nb_bufs = _recv_raw_pkts_vec(rxq, rx_pkts, nb_pkts,

After this _recv_raw_pkts_vec it checks 32 bytes in split_flags (4x8
bytes), that can overrun or miss some flags.
Btw. Bruce just fixed that part in "ixgbe: fix check for split packets"

Thanks for all these valuable comments, will keep the max burst size 32.