From patchwork Mon Sep 21 19:22:54 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Honnappa Nagarahalli X-Patchwork-Id: 78215 X-Patchwork-Delegate: ferruh.yigit@amd.com Return-Path: X-Original-To: patchwork@inbox.dpdk.org Delivered-To: patchwork@inbox.dpdk.org Received: from dpdk.org (dpdk.org [92.243.14.124]) by inbox.dpdk.org (Postfix) with ESMTP id D51BCA04DD; Mon, 21 Sep 2020 21:23:36 +0200 (CEST) Received: from [92.243.14.124] (localhost [127.0.0.1]) by dpdk.org (Postfix) with ESMTP id 3CC641DA7D; Mon, 21 Sep 2020 21:23:19 +0200 (CEST) Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by dpdk.org (Postfix) with ESMTP id B181D1D9E2; Mon, 21 Sep 2020 21:23:14 +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 337F61045; Mon, 21 Sep 2020 12:23:14 -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 22FBC3F718; Mon, 21 Sep 2020 12:23:14 -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 14:22:54 -0500 Message-Id: <20200921192254.20560-4-honnappa.nagarahalli@arm.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20200921192254.20560-1-honnappa.nagarahalli@arm.com> References: <20200921192254.20560-1-honnappa.nagarahalli@arm.com> Subject: [dpdk-dev] [PATCH 4/4] net/memif: relax the load of ring head pointer for M2S ring 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" For M2S rings, ring->head is updated by the receiver and eth_memif_rx function is called in the context of receiving 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 Reviewed-by: Phil Yang --- drivers/net/memif/rte_eth_memif.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/drivers/net/memif/rte_eth_memif.c b/drivers/net/memif/rte_eth_memif.c index 435c6345c..1cbb1fd7a 100644 --- a/drivers/net/memif/rte_eth_memif.c +++ b/drivers/net/memif/rte_eth_memif.c @@ -405,7 +405,11 @@ eth_memif_rx(void *queue, struct rte_mbuf **bufs, uint16_t nb_pkts) refill: if (type == MEMIF_RING_M2S) { - head = __atomic_load_n(&ring->head, __ATOMIC_ACQUIRE); + /* 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_RELAXED); n_slots = ring_size - head + mq->last_tail; while (n_slots--) {