[2/4] net/memif: relax the load of ring tail pointer for M2S ring
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Commit Message
For M2S rings, ring->tail is updated by the sender and eth_memif_tx
function is called in the context of sending thread. The loads in
the sender do not need to synchronize with its own stores.
Fixes: a2aafb9aa651 ("net/memif: optimize with one-way barrier")
Cc: phil.yang@arm.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 | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
@@ -573,7 +573,13 @@ eth_memif_tx(void *queue, struct rte_mbuf **bufs, uint16_t nb_pkts)
n_free = ring_size - slot +
__atomic_load_n(&ring->tail, __ATOMIC_ACQUIRE);
} else {
- slot = __atomic_load_n(&ring->tail, __ATOMIC_ACQUIRE);
+ /* For M2S queues ring->tail is updated by the sender and
+ * this function is called in the context of sending thread.
+ * The loads in the sender do not need to synchronize with
+ * its own stores. Hence, the following load can be a
+ * relaxed load.
+ */
+ slot = __atomic_load_n(&ring->tail, __ATOMIC_RELAXED);
n_free = __atomic_load_n(&ring->head, __ATOMIC_ACQUIRE) - slot;
}