[dpdk-dev] [PATCH] ixgbe: fix checking for tx_free_thresh

[Zoltan Kiss <zoltan.kiss@linaro.org>]

This check doesn't do what's required by rte_eth_tx_burst:
"When the number of previously sent packets reached the "minimum transmit
packets to free" threshold"

This can cause problems when txq->tx_free_thresh + [number of elements in the
pool] < txq->nb_tx_desc.

Signed-off-by: Zoltan Kiss <zoltan.kiss@linaro.org>
---
 drivers/net/ixgbe/ixgbe_rxtx.c     | 4 ++--
 drivers/net/ixgbe/ixgbe_rxtx_vec.c | 2 +-
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/net/ixgbe/ixgbe_rxtx.c b/drivers/net/ixgbe/ixgbe_rxtx.c
index 4f9ab22..b70ed8c 100644
--- a/drivers/net/ixgbe/ixgbe_rxtx.c
+++ b/drivers/net/ixgbe/ixgbe_rxtx.c
@@ -250,10 +250,10 @@ tx_xmit_pkts(void *tx_queue, struct rte_mbuf **tx_pkts,
 
 	/*
 	 * Begin scanning the H/W ring for done descriptors when the
-	 * number of available descriptors drops below tx_free_thresh.  For
+	 * number of in flight descriptors reaches tx_free_thresh. For
 	 * each done descriptor, free the associated buffer.
 	 */
-	if (txq->nb_tx_free < txq->tx_free_thresh)
+	if ((txq->nb_tx_desc - txq->nb_tx_free) > txq->tx_free_thresh)
 		ixgbe_tx_free_bufs(txq);
 
 	/* Only use descriptors that are available */
diff --git a/drivers/net/ixgbe/ixgbe_rxtx_vec.c b/drivers/net/ixgbe/ixgbe_rxtx_vec.c
index abd10f6..f91c698 100644
--- a/drivers/net/ixgbe/ixgbe_rxtx_vec.c
+++ b/drivers/net/ixgbe/ixgbe_rxtx_vec.c
@@ -598,7 +598,7 @@ ixgbe_xmit_pkts_vec(void *tx_queue, struct rte_mbuf **tx_pkts,
 	if (unlikely(nb_pkts > RTE_IXGBE_VPMD_TX_BURST))
 		nb_pkts = RTE_IXGBE_VPMD_TX_BURST;
 
-	if (txq->nb_tx_free < txq->tx_free_thresh)
+	if ((txq->nb_tx_desc - txq->nb_tx_free) > txq->tx_free_thresh)
 		ixgbe_tx_free_bufs(txq);
 
 	nb_commit = nb_pkts = (uint16_t)RTE_MIN(txq->nb_tx_free, nb_pkts);
-- 
1.9.1