From patchwork Wed Dec 9 15:03:03 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Loic Poulain X-Patchwork-Id: 341726 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-18.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER, INCLUDES_PATCH, MAILING_LIST_MULTI, SPF_HELO_NONE, SPF_PASS, URIBL_BLOCKED, USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 00D7FC433FE for ; Wed, 9 Dec 2020 14:57:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C064323A33 for ; Wed, 9 Dec 2020 14:57:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387411AbgLIO5W (ORCPT ); Wed, 9 Dec 2020 09:57:22 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40748 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732445AbgLIO5V (ORCPT ); Wed, 9 Dec 2020 09:57:21 -0500 Received: from mail-wm1-x344.google.com (mail-wm1-x344.google.com [IPv6:2a00:1450:4864:20::344]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B0231C0617A6 for ; Wed, 9 Dec 2020 06:56:04 -0800 (PST) Received: by mail-wm1-x344.google.com with SMTP id y23so1973441wmi.1 for ; Wed, 09 Dec 2020 06:56:04 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=from:to:cc:subject:date:message-id:in-reply-to:references; bh=BGfO0Eswp9lnQgcF2ohJFOorqCfHltMpUAVxKVdPxlo=; b=im9mHqn8LdwMxu6IhAbVxZnVNQ+4/qD1xBFo0uH8GNlSEQhzz8/sr9yYNG/Eb5lpbK wtvOVV5KnB3H+X70nu7LEY7+VJ2T9A/Ysmd+HoUlIvRO2pMKCsynqSjjiy7P+M33MhaS QP66LBsuAWbkuRO33O0sl+12fTzxPvoMgtMFIBqxlv0+OUHsvrHEaNwgeZheq0WLCGuZ 5hAQO12tYu8H32zQ0ys1atozuIztG7feqejrNncZa72cAZb+M1Zxunv7FXVfZ6NRBd0S 3xjvf9jyjKrz74badLuubGWcuqRPyEqTsCJr7yMRXe9NcbpYqL2iQT0DO5wTqZuABDNM YgZw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references; bh=BGfO0Eswp9lnQgcF2ohJFOorqCfHltMpUAVxKVdPxlo=; b=ehfhmMx0g7ff0Pzu+BHh59bXVZ7PXbGdscy1MRRxOy0LdIMYxVyFlpfRQK8/xmK7m7 TEeh8mHVheD7VWWswnFCuftP2FvHEl49DbSdtZL0oOZXzMlkmPoQh/WDhVeUdi3X9hu+ 5in5C4VQTiLDopmCV5doytX0/rOF/BXjeah/QnCFUk8O4i8aEqfvoDrtQpxPA02Cfvjl 1hXjrH5eLNhTV/g3XK98G7/HYEzQjfWlWj0puS48sS+LuA2U2lAaAIJ585y7dMtbfzMq cYYqPx/LmnR+ghD/rotSc9KVnt5e3C5YZAxKxnWLJKQqmPRRb/2+N5cFV1BbjvLz7Zn0 LKSg== X-Gm-Message-State: AOAM530oXL1O4B141URcs3xB+eNJ6UnEC/uSKO/qax0LLa9PULv67zRr cvp9NrKfApOXO4S4HsjpSSwJjg== X-Google-Smtp-Source: ABdhPJyPltzQtqNtstQ8+RvYR+AVwDF3My4GECRIoAhYYMNCmIAbhke7jNJnFYU8qIYzRut6/4QlIw== X-Received: by 2002:a1c:7318:: with SMTP id d24mr3263440wmb.39.1607525763428; Wed, 09 Dec 2020 06:56:03 -0800 (PST) Received: from localhost.localdomain ([2a01:e0a:490:8730:c728:53f6:5e7e:2f63]) by smtp.gmail.com with ESMTPSA id i11sm3782219wrm.1.2020.12.09.06.56.02 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Wed, 09 Dec 2020 06:56:03 -0800 (PST) From: Loic Poulain To: kuba@kernel.org Cc: manivannan.sadhasivam@linaro.org, linux-arm-msm@vger.kernel.org, netdev@vger.kernel.org, davem@davemloft.net, Loic Poulain Subject: [PATCH 3/3] net: mhi: Add dedicated alloc thread Date: Wed, 9 Dec 2020 16:03:03 +0100 Message-Id: <1607526183-25652-3-git-send-email-loic.poulain@linaro.org> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1607526183-25652-1-git-send-email-loic.poulain@linaro.org> References: <1607526183-25652-1-git-send-email-loic.poulain@linaro.org> Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org The buffer allocation for RX path is currently done by a work executed in the system workqueue. The work to do is quite simple and consists mostly in allocating and queueing as much as possible buffers to the MHI RX channel. It appears that using a dedicated kthread would be more appropriate to prevent 1. RX allocation latency introduced by the system queue 2. Unbounded work execution, the work only returning when queue is full, it can possibly monopolise the workqueue thread on slower systems. This patch replaces the system work with a simple kthread that loops on buffer allocation and sleeps when queue is full. Moreover it gets rid of the local rx_queued variable (to track buffer count), and instead, relies on the new mhi_get_free_desc_count helper. After pratical testing on a x86_64 machine, this change improves - Peek throughput (slightly, by few mbps) - Throughput stability when concurrent loads are running (stress) - CPU usage, less CPU cycles dedicated to the task Below is the powertop output for RX allocation task before and after this change, when performing UDP download at 6Gbps. Mostly to highlight the improvement in term of CPU usage. older (system workqueue): Usage Events/s Category Description 63,2 ms/s 134,0 kWork mhi_net_rx_refill_work 62,8 ms/s 134,3 kWork mhi_net_rx_refill_work 60,8 ms/s 141,4 kWork mhi_net_rx_refill_work newer (dedicated kthread): Usage Events/s Category Description 20,7 ms/s 155,6 Process [PID 3360] [mhi-net-rx] 22,2 ms/s 169,6 Process [PID 3360] [mhi-net-rx] 22,3 ms/s 150,2 Process [PID 3360] [mhi-net-rx] Signed-off-by: Loic Poulain --- drivers/net/mhi_net.c | 98 ++++++++++++++++++++++++++------------------------- 1 file changed, 50 insertions(+), 48 deletions(-) diff --git a/drivers/net/mhi_net.c b/drivers/net/mhi_net.c index 0333e07..eef40f5 100644 --- a/drivers/net/mhi_net.c +++ b/drivers/net/mhi_net.c @@ -5,6 +5,7 @@ */ #include +#include #include #include #include @@ -25,7 +26,6 @@ struct mhi_net_stats { u64_stats_t tx_bytes; u64_stats_t tx_errors; u64_stats_t tx_dropped; - atomic_t rx_queued; struct u64_stats_sync tx_syncp; struct u64_stats_sync rx_syncp; }; @@ -33,17 +33,59 @@ struct mhi_net_stats { struct mhi_net_dev { struct mhi_device *mdev; struct net_device *ndev; - struct delayed_work rx_refill; + struct task_struct *refill_task; + wait_queue_head_t refill_wq; struct mhi_net_stats stats; u32 rx_queue_sz; }; +static int mhi_net_refill_thread(void *data) +{ + struct mhi_net_dev *mhi_netdev = data; + struct net_device *ndev = mhi_netdev->ndev; + struct mhi_device *mdev = mhi_netdev->mdev; + int size = READ_ONCE(ndev->mtu); + struct sk_buff *skb; + int err; + + while (1) { + err = wait_event_interruptible(mhi_netdev->refill_wq, + !mhi_queue_is_full(mdev, DMA_FROM_DEVICE) + || kthread_should_stop()); + if (err || kthread_should_stop()) + break; + + skb = netdev_alloc_skb(ndev, size); + if (unlikely(!skb)) { + /* No memory, retry later */ + schedule_timeout_interruptible(msecs_to_jiffies(250)); + continue; + } + + err = mhi_queue_skb(mdev, DMA_FROM_DEVICE, skb, size, MHI_EOT); + if (unlikely(err)) { + net_err_ratelimited("%s: Failed to queue RX buf (%d)\n", + ndev->name, err); + kfree_skb(skb); + break; + } + + /* Do not hog the CPU */ + cond_resched(); + } + + return 0; +} + static int mhi_ndo_open(struct net_device *ndev) { struct mhi_net_dev *mhi_netdev = netdev_priv(ndev); - /* Feed the rx buffer pool */ - schedule_delayed_work(&mhi_netdev->rx_refill, 0); + mhi_netdev->refill_task = kthread_run(mhi_net_refill_thread, mhi_netdev, + "mhi-net-rx"); + if (IS_ERR(mhi_netdev->refill_task)) { + return PTR_ERR(mhi_netdev->refill_task); + } /* Carrier is established via out-of-band channel (e.g. qmi) */ netif_carrier_on(ndev); @@ -57,9 +99,9 @@ static int mhi_ndo_stop(struct net_device *ndev) { struct mhi_net_dev *mhi_netdev = netdev_priv(ndev); + kthread_stop(mhi_netdev->refill_task); netif_stop_queue(ndev); netif_carrier_off(ndev); - cancel_delayed_work_sync(&mhi_netdev->rx_refill); return 0; } @@ -138,9 +180,6 @@ static void mhi_net_dl_callback(struct mhi_device *mhi_dev, { struct mhi_net_dev *mhi_netdev = dev_get_drvdata(&mhi_dev->dev); struct sk_buff *skb = mhi_res->buf_addr; - int remaining; - - remaining = atomic_dec_return(&mhi_netdev->stats.rx_queued); if (unlikely(mhi_res->transaction_status)) { dev_kfree_skb_any(skb); @@ -163,9 +202,8 @@ static void mhi_net_dl_callback(struct mhi_device *mhi_dev, netif_rx(skb); } - /* Refill if RX buffers queue becomes low */ - if (remaining <= mhi_netdev->rx_queue_sz / 2) - schedule_delayed_work(&mhi_netdev->rx_refill, 0); + if (mhi_get_free_desc_count(mhi_dev, DMA_FROM_DEVICE) >= mhi_netdev->rx_queue_sz / 3) + wake_up_interruptible(&mhi_netdev->refill_wq); } static void mhi_net_ul_callback(struct mhi_device *mhi_dev, @@ -200,42 +238,6 @@ static void mhi_net_ul_callback(struct mhi_device *mhi_dev, netif_wake_queue(ndev); } -static void mhi_net_rx_refill_work(struct work_struct *work) -{ - struct mhi_net_dev *mhi_netdev = container_of(work, struct mhi_net_dev, - rx_refill.work); - struct net_device *ndev = mhi_netdev->ndev; - struct mhi_device *mdev = mhi_netdev->mdev; - int size = READ_ONCE(ndev->mtu); - struct sk_buff *skb; - int err; - - while (atomic_read(&mhi_netdev->stats.rx_queued) < mhi_netdev->rx_queue_sz) { - skb = netdev_alloc_skb(ndev, size); - if (unlikely(!skb)) - break; - - err = mhi_queue_skb(mdev, DMA_FROM_DEVICE, skb, size, MHI_EOT); - if (unlikely(err)) { - net_err_ratelimited("%s: Failed to queue RX buf (%d)\n", - ndev->name, err); - kfree_skb(skb); - break; - } - - atomic_inc(&mhi_netdev->stats.rx_queued); - - /* Do not hog the CPU if rx buffers are consumed faster than - * queued (unlikely). - */ - cond_resched(); - } - - /* If we're still starved of rx buffers, reschedule later */ - if (unlikely(!atomic_read(&mhi_netdev->stats.rx_queued))) - schedule_delayed_work(&mhi_netdev->rx_refill, HZ / 2); -} - static int mhi_net_probe(struct mhi_device *mhi_dev, const struct mhi_device_id *id) { @@ -256,7 +258,7 @@ static int mhi_net_probe(struct mhi_device *mhi_dev, mhi_netdev->mdev = mhi_dev; SET_NETDEV_DEV(ndev, &mhi_dev->dev); - INIT_DELAYED_WORK(&mhi_netdev->rx_refill, mhi_net_rx_refill_work); + init_waitqueue_head(&mhi_netdev->refill_wq); u64_stats_init(&mhi_netdev->stats.rx_syncp); u64_stats_init(&mhi_netdev->stats.tx_syncp);