[1/4] net/memif: do not update local copy of tail in tx function
diff mbox series

Message ID 20200921192254.20560-1-honnappa.nagarahalli@arm.com
State Superseded
Delegated to: Ferruh Yigit
Headers show
  • [1/4] net/memif: do not update local copy of tail in tx function
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Context Check Description
ci/checkpatch success coding style OK

Commit Message

Honnappa Nagarahalli Sept. 21, 2020, 7:22 p.m. UTC
In the case of S2M queues, the receiver synchronizes with the sender
(i.e. informs of the packets it has received) using ring->tail.
Hence, the sender does not need to update last_tail.

In the case of M2S queues, the receiver uses last_tail to
keep track of the descriptors it has received. The
sender is not required to update the last_tail. Updating
the last_tail makes it a shared variable between the
transmitter and receiver affecting the performance.

Fixes: 09c7e63a71f9 ("net/memif: introduce memory interface PMD")
Cc: jgrajcia@cisco.com
Cc: stable@dpdk.org

Signed-off-by: Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>
Reviewed-by: Phil Yang <phil.yang@arm.com>
 drivers/net/memif/rte_eth_memif.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff mbox series

diff --git a/drivers/net/memif/rte_eth_memif.c b/drivers/net/memif/rte_eth_memif.c
index c1c7e9f8d..fd7dbc53e 100644
--- a/drivers/net/memif/rte_eth_memif.c
+++ b/drivers/net/memif/rte_eth_memif.c
@@ -568,12 +568,10 @@  eth_memif_tx(void *queue, struct rte_mbuf **bufs, uint16_t nb_pkts)
 	ring_size = 1 << mq->log2_ring_size;
 	mask = ring_size - 1;
-	n_free = __atomic_load_n(&ring->tail, __ATOMIC_ACQUIRE) - mq->last_tail;
-	mq->last_tail += n_free;
 	if (type == MEMIF_RING_S2M) {
 		slot = __atomic_load_n(&ring->head, __ATOMIC_ACQUIRE);
-		n_free = ring_size - slot + mq->last_tail;
+		n_free = ring_size - slot +
+				__atomic_load_n(&ring->tail, __ATOMIC_ACQUIRE);
 	} else {
 		slot = __atomic_load_n(&ring->tail, __ATOMIC_ACQUIRE);
 		n_free = __atomic_load_n(&ring->head, __ATOMIC_ACQUIRE) - slot;