From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from dpdk.org (dpdk.org [92.243.14.124]) by inbox.dpdk.org (Postfix) with ESMTP id E8CB0A04DD; Mon, 21 Sep 2020 21:23:13 +0200 (CEST) Received: from [92.243.14.124] (localhost [127.0.0.1]) by dpdk.org (Postfix) with ESMTP id 484D31D977; Mon, 21 Sep 2020 21:23:13 +0200 (CEST) Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by dpdk.org (Postfix) with ESMTP id 7B3B21D94B; Mon, 21 Sep 2020 21:23:11 +0200 (CEST) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id BD5411045; Mon, 21 Sep 2020 12:23:09 -0700 (PDT) Received: from qc2400f-1.austin.arm.com (qc2400f-1.austin.arm.com [10.118.12.27]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id AC1E43F718; Mon, 21 Sep 2020 12:23:09 -0700 (PDT) From: Honnappa Nagarahalli To: dev@dpdk.org, honnappa.nagarahalli@arm.com, phil.yang@arm.com, jgrajcia@cisco.com, ferruh.yigit@intel.com Cc: nd@arm.com, stable@dpdk.org Date: Mon, 21 Sep 2020 14:22:51 -0500 Message-Id: <20200921192254.20560-1-honnappa.nagarahalli@arm.com> X-Mailer: git-send-email 2.17.1 Subject: [dpdk-dev] [PATCH 1/4] net/memif: do not update local copy of tail in tx function X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org Sender: "dev" 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 Reviewed-by: Phil Yang --- drivers/net/memif/rte_eth_memif.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-) 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; -- 2.17.1