From patchwork Mon Sep 28 19:03:33 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Honnappa Nagarahalli X-Patchwork-Id: 313684 Delivered-To: patch@linaro.org Received: by 2002:a92:5ad1:0:0:0:0:0 with SMTP id b78csp3546572ilg; Mon, 28 Sep 2020 12:06:10 -0700 (PDT) X-Google-Smtp-Source: ABdhPJxXAKqtKOjppkNsC++ehsph6uvitF0oj4hBkhKy68mva26TuRC7Xjiq/wtxkhmQarW1Er1c X-Received: by 2002:a17:906:8508:: with SMTP id i8mr252528ejx.390.1601319970055; Mon, 28 Sep 2020 12:06:10 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1601319970; cv=none; d=google.com; s=arc-20160816; b=pQgvjcpcgc9P9Uvk25tOZuHBW478sbfy2nhgjw3ZEHRm9YI7l+WmnbCi0h/lINaBzA ROegwXJiNCIGb+SN18NAG+5Si0H5QaWIOvo2ih5i+/tewtN66QFhsFxF7FNTv8GodtMS /5EHtJTHy6TYsNFBOtatKdRXTzfkDbxMEz1rGJGRA0VarWyYjZLkCqU1Cmpbq08/Hqy9 qbu59BMEPpsjiVng6XNbaVTIkh/8fTVn8+d3wgxYYrkd/4gF8wAJCmpJ53x47M42TQos EEV1PHDXNGtmSuzbAftZTtfG9CmG9341j36CkCvLzw3/qn6zp2uZqcpASIqFdvTMwxKz weTg== 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=B5eSf1+B5bz81Do4s2efPEUVD7dIGpfeh+AIqK3r4eo=; b=I8A3dkm1QwG4zzLfoVLC3FLA4Li5Ke8Wh3X5iIC7ATtJByT8be3mMNYH7hKqdbx37W AQ1CmDLjBC+HGImxkqHwcoC/0Z4kZ/p/RcqhICDAQwHT2/4YDUcBiioJgNYnmgPD5unu AOzbIEQN5L6N2QrZ4ME1k5FTiZl5Otp8r0zfzgqlK/Arg3zg32MUwkhUtWu6rCjGuxB3 AIRRcWHMQJtwzS9IAT4wOncHpKEdDi7IRDvNZtCsr6f4j9uY8/mnhgDYI0lC1Q0bbX00 RI5I9qPymxt6Bjda4VELiviPIubDGoTL9yYWR2qM18BImsrddMr3wa5VBDcnFITvNruh Y35Q== 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 c17si1240539ejx.205.2020.09.28.12.06.09; Mon, 28 Sep 2020 12:06:10 -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 973521D6DF; Mon, 28 Sep 2020 21:04:18 +0200 (CEST) Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by dpdk.org (Postfix) with ESMTP id AC2931D5D8 for ; Mon, 28 Sep 2020 21:04:08 +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 E67371500; Mon, 28 Sep 2020 12:04:07 -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 D68493F70D; Mon, 28 Sep 2020 12:04:07 -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 14:03:33 -0500 Message-Id: <20200928190334.40624-7-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 7/8] net/memif: relax the load of ring head pointer for S2M 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 S2M rings, ring->head is updated by the sender and eth_memif_tx_zc function is called in the context of sending thread. The loads in the sender 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 | 14 ++++++++++---- 1 file changed, 10 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 9babd073a..704350022 100644 --- a/drivers/net/memif/rte_eth_memif.c +++ b/drivers/net/memif/rte_eth_memif.c @@ -752,11 +752,13 @@ eth_memif_tx_zc(void *queue, struct rte_mbuf **bufs, uint16_t nb_pkts) memif_free_stored_mbufs(proc_private, mq); /* ring type always MEMIF_RING_S2M */ - /* 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. + /* For S2M queues ring->head 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->head, __ATOMIC_ACQUIRE); + slot = __atomic_load_n(&ring->head, __ATOMIC_RELAXED); n_free = ring_size - slot + mq->last_tail; int used_slots; @@ -812,6 +814,10 @@ eth_memif_tx_zc(void *queue, struct rte_mbuf **bufs, uint16_t nb_pkts) no_free_slots: /* ring type always MEMIF_RING_S2M */ + /* 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_rx for S2M rings. + */ __atomic_store_n(&ring->head, slot, __ATOMIC_RELEASE); /* Send interrupt, if enabled. */