From patchwork Mon Sep 28 19:03:31 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Honnappa Nagarahalli X-Patchwork-Id: 313683 Delivered-To: patch@linaro.org Received: by 2002:a92:5ad1:0:0:0:0:0 with SMTP id b78csp3546304ilg; Mon, 28 Sep 2020 12:05:50 -0700 (PDT) X-Google-Smtp-Source: ABdhPJxkEKo4vrLPmc51ua5L/z8xY7H6yudIb5qMAtNJ74jdbIpygMhhW8LQT9lIJhMeOUwyW3hg X-Received: by 2002:a17:906:95cd:: with SMTP id n13mr199990ejy.297.1601319950102; Mon, 28 Sep 2020 12:05:50 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1601319950; cv=none; d=google.com; s=arc-20160816; b=tMxDqpgNuORgIupTLxifdWDVwCjDV73aWoJ1vxf78P0UlkrVmJIDwFoLv613/7uHJ7 3Jw4tVaEx/kZH+w5uRLi2e/GrkZa1xEiJk0ZI3/E9dwQUPA8Kp/RXU/OJr22T9X1hEtp ZkfjquMQ0tMho84m0j39tSmqG/0idJ0d7nRYZMJUm9ggHzOLBaOILHT276j8KgP+/J5a ap+eu8ppzjcZVgBfaj6zYNEKJc1iAAiLM5/iReFrkTmjYHHVKf4bUQCo9mZ35Q5d0mZ1 MX3o+WD16PR7k+Syh8337LvvM3JPGqUl/skeOBtYC8idm6uahYpZQFzvWUi7EOS6qESK qZmQ== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=sender:errors-to:list-subscribe:list-help:list-post:list-archive :list-unsubscribe:list-id:precedence:subject:references:in-reply-to :message-id:date:cc:to:from; bh=YogujJsej78DpRuEJcZp9SZF/RTDOyET7qHo0Ua0RLs=; b=S0nscV9KrXI659K5BVvDVTUJQtK8qyGEwvh+4EKgqVVQdqyMurAbdQxdDi4/OOfAOk xuSD7R6iS/ROawTQ8YnkEVzWCIFytmIjRQtTAquZKbs206Q53dhZqz1YTlkl3NFBTiI8 jPKgfkSrF1HXDGyQPwCP0p3+ybWQVsEJ49gRudQUvlkoP2dQJYTdbHDhXpw0OnbRVTJ2 zsSLLMOTg0dc1EGTjV0XDe48V0P7rsleF6q9FCvJRwr5Rrzq4VJ62997MSuWI3YqQFog /JHRFJCPyp6Bl1Ktdsqs1IdXM2s9nkYBJbuNZpynygg68/PcIitFpWdN7DyfadGeBtQX 2WvA== ARC-Authentication-Results: i=1; mx.google.com; spf=pass (google.com: domain of dev-bounces@dpdk.org designates 92.243.14.124 as permitted sender) smtp.mailfrom=dev-bounces@dpdk.org Return-Path: Received: from dpdk.org (dpdk.org. [92.243.14.124]) by mx.google.com with ESMTP id c3si1133521ejk.666.2020.09.28.12.05.49; Mon, 28 Sep 2020 12:05:50 -0700 (PDT) Received-SPF: pass (google.com: domain of dev-bounces@dpdk.org designates 92.243.14.124 as permitted sender) client-ip=92.243.14.124; Authentication-Results: mx.google.com; spf=pass (google.com: domain of dev-bounces@dpdk.org designates 92.243.14.124 as permitted sender) smtp.mailfrom=dev-bounces@dpdk.org Received: from [92.243.14.124] (localhost [127.0.0.1]) by dpdk.org (Postfix) with ESMTP id 1F03F1D6D0; Mon, 28 Sep 2020 21:04:17 +0200 (CEST) Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by dpdk.org (Postfix) with ESMTP id 870CC1D681 for ; Mon, 28 Sep 2020 21:04:09 +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 CE03D14F6; Mon, 28 Sep 2020 12:04:06 -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 BE40F3F70D; Mon, 28 Sep 2020 12:04:06 -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 Date: Mon, 28 Sep 2020 14:03:31 -0500 Message-Id: <20200928190334.40624-5-honnappa.nagarahalli@arm.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20200928190334.40624-1-honnappa.nagarahalli@arm.com> References: <20200921192254.20560-1-honnappa.nagarahalli@arm.com> <20200928190334.40624-1-honnappa.nagarahalli@arm.com> Subject: [dpdk-dev] [PATCH v2 5/8] net/memif: relax the load of ring head pointer for M2S zc 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 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 Reviewed-by: Phil Yang Reviewed-by: Ruifeng Wang --- drivers/net/memif/rte_eth_memif.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-) -- 2.17.1 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;