From: Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>
To: dev@dpdk.org, honnappa.nagarahalli@arm.com, phil.yang@arm.com,
jgrajcia@cisco.com, ferruh.yigit@intel.com
Cc: nd@arm.com
Subject: [dpdk-dev] [PATCH v2 5/8] net/memif: relax the load of ring head pointer for M2S zc ring
Date: Mon, 28 Sep 2020 14:03:31 -0500 [thread overview]
Message-ID: <20200928190334.40624-5-honnappa.nagarahalli@arm.com> (raw)
In-Reply-To: <20200928190334.40624-1-honnappa.nagarahalli@arm.com>
For zero-copy M2S rings, ring->head is updated by the receiver
and eth_memif_rx_zc function is called in the context of
receiving thread. The loads in the receiver do not need to
synchronize with its own stores.
Signed-off-by: Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>
Reviewed-by: Phil Yang <phil.yang@arm.com>
Reviewed-by: Ruifeng Wang <ruifeng.wang@arm.com>
---
drivers/net/memif/rte_eth_memif.c | 12 ++++++++----
1 file changed, 8 insertions(+), 4 deletions(-)
diff --git a/drivers/net/memif/rte_eth_memif.c b/drivers/net/memif/rte_eth_memif.c
index 96db76121..404c86ae8 100644
--- a/drivers/net/memif/rte_eth_memif.c
+++ b/drivers/net/memif/rte_eth_memif.c
@@ -514,11 +514,11 @@ eth_memif_rx_zc(void *queue, struct rte_mbuf **bufs, uint16_t nb_pkts)
/* Supply master with new buffers */
refill:
- /* The ring->head acts as a guard variable between Tx and Rx
- * threads, so using load-acquire pairs with store-release
- * to synchronize it between threads.
+ /* ring->head is updated by the receiver and this function
+ * is called in the context of receiver thread. The loads in
+ * the receiver do not need to synchronize with its own stores.
*/
- head = __atomic_load_n(&ring->head, __ATOMIC_ACQUIRE);
+ head = __atomic_load_n(&ring->head, __ATOMIC_RELAXED);
n_slots = ring_size - head + mq->last_tail;
if (n_slots < 32)
@@ -543,6 +543,10 @@ eth_memif_rx_zc(void *queue, struct rte_mbuf **bufs, uint16_t nb_pkts)
(uint8_t *)proc_private->regions[d0->region]->addr;
}
no_free_mbufs:
+ /* The ring->head acts as a guard variable between Tx and Rx
+ * threads, so using store-release pairs with load-acquire
+ * in function eth_memif_tx.
+ */
__atomic_store_n(&ring->head, head, __ATOMIC_RELEASE);
mq->n_pkts += n_rx_pkts;
--
2.17.1
next prev parent reply other threads:[~2020-09-28 19:05 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-21 19:22 [dpdk-dev] [PATCH 1/4] net/memif: do not update local copy of tail in tx function Honnappa Nagarahalli
2020-09-21 19:22 ` [dpdk-dev] [PATCH 2/4] net/memif: relax the load of ring tail pointer for M2S ring Honnappa Nagarahalli
2020-09-21 19:22 ` [dpdk-dev] [PATCH 3/4] net/memif: relax the load of ring head pointer for S2M ring Honnappa Nagarahalli
2020-09-21 19:22 ` [dpdk-dev] [PATCH 4/4] net/memif: relax the load of ring head pointer for M2S ring Honnappa Nagarahalli
2020-09-28 19:03 ` [dpdk-dev] [PATCH v2 1/8] net/memif: do not update local copy of tail in tx function Honnappa Nagarahalli
2020-09-28 19:03 ` [dpdk-dev] [PATCH v2 2/8] net/memif: relax the load of ring tail pointer for M2S ring Honnappa Nagarahalli
2020-09-28 19:03 ` [dpdk-dev] [PATCH v2 3/8] net/memif: relax the load of ring head " Honnappa Nagarahalli
2020-09-28 19:03 ` [dpdk-dev] [PATCH v2 4/8] net/memif: relax the load of ring head pointer for S2M ring Honnappa Nagarahalli
2020-09-28 19:03 ` Honnappa Nagarahalli [this message]
2020-09-28 19:03 ` [dpdk-dev] [PATCH v2 6/8] net/memif: remove extra check Honnappa Nagarahalli
2020-09-28 19:03 ` [dpdk-dev] [PATCH v2 7/8] net/memif: relax the load of ring head pointer for S2M zc ring Honnappa Nagarahalli
2020-09-28 19:03 ` [dpdk-dev] [PATCH v2 8/8] net/memif: move the barrier outside the loop Honnappa Nagarahalli
2020-09-28 20:53 ` [dpdk-dev] [PATCH v2 1/8] net/memif: do not update local copy of tail in tx function Stephen Hemminger
2020-09-29 5:24 ` Honnappa Nagarahalli
2020-10-07 17:08 ` Honnappa Nagarahalli
2020-10-09 11:23 ` Jakub Grajciar -X (jgrajcia - PANTHEON TECH SRO at Cisco)
2020-10-09 15:59 ` Ferruh Yigit
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