From patchwork Wed Dec 9 00:54:43 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Wei Wang X-Patchwork-Id: 340894 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=-26.2 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, 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,USER_IN_DEF_DKIM_WL autolearn=ham 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 8C08EC19437 for ; Wed, 9 Dec 2020 00:55:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 497B02229C for ; Wed, 9 Dec 2020 00:55:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725208AbgLIAzi (ORCPT ); Tue, 8 Dec 2020 19:55:38 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52556 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725768AbgLIAzh (ORCPT ); Tue, 8 Dec 2020 19:55:37 -0500 Received: from mail-qk1-x74a.google.com (mail-qk1-x74a.google.com [IPv6:2607:f8b0:4864:20::74a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E6367C06179C for ; Tue, 8 Dec 2020 16:54:50 -0800 (PST) Received: by mail-qk1-x74a.google.com with SMTP id t127so189060qkf.0 for ; Tue, 08 Dec 2020 16:54:50 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=sender:date:in-reply-to:message-id:mime-version:references:subject :from:to:cc; bh=5OkKxgxDxxYnQ0ng7/ZnEnQTthDelIY86K9kd2On1/Y=; b=fCz2fIQJ3Oda7bPq/hzJlTifv6+d+eprOz45wq/fJwKNiFRd4ljgyX4y/wltr5ZlUA 9bhXwKdxnTdYitj4xo9P2tSOxBfL3zNrSMYXtR3378zukUirh/MZFiAXTgdfh8VSY5Yv L+oLo7tWutcFwh6VOIPqesIeL/SpfX5GSzaNHNelXHQhk8+K8pXHAgUy4zf6NS/Q9ixn +H25P9Cn7iafFX20dYoiaD6fLCW+tWpB4HestU+RjxcfhEEyMj+lpXeBPmkDyFZorw8O W39uAFe2ZLT7/3tWytfWhhTU3N4JcYhOV2meMfzCDtc3C4UmTc0T68A5/YJgAZOKijiO ZMCg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:sender:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=5OkKxgxDxxYnQ0ng7/ZnEnQTthDelIY86K9kd2On1/Y=; b=Tg5ZsYnneMo/JTZZmq37Gzr6eJ7X60LJ4nwwzkHz58OngxoopGdA/LKz8wqPnOxwRM +PKSp6KDByvxTfwCVN/hQJ9hokzY/dswwW28ooKAgef60hrh9K0odNtyePhvw1sWIhC1 3PiKA/RKn0iYTgY/uCSodWiLkLJcF0tpEhjeaJmRsK+zUmz8T1mfX/QH1px29H9Aav1O xFSHiHOw5XCnsuYVM+uccAZxYnsUYPYLqyjsn/1gM6USg2jlx5vHCOpTfeWzmh3pigT3 iJ0ztzPT70tMHH3Lx8eqETO6+p/Leg2mNxdZKO7YfreXsW++Q//U+MU7SOgMD4HFA4uz VXMw== X-Gm-Message-State: AOAM532VqiLvunGGogDKck8yri3i2OcIXkyngaYmj+0DipHC3dTzlryj /W4CTtt8ITWue+q/K2i2q4TlaYZHHyM= X-Google-Smtp-Source: ABdhPJzktaCyiHqEDHiniMaumGrrJu1xbr1PiQJdIXYwHaR3my9nRJrCbXgcyDVgE5sTlwOxkAyiHRtZHWc= Sender: "weiwan via sendgmr" X-Received: from weiwan.svl.corp.google.com ([2620:15c:2c4:201:1ea0:b8ff:fe75:cf08]) (user=weiwan job=sendgmr) by 2002:a0c:f046:: with SMTP id b6mr285531qvl.14.1607475290114; Tue, 08 Dec 2020 16:54:50 -0800 (PST) Date: Tue, 8 Dec 2020 16:54:43 -0800 In-Reply-To: <20201209005444.1949356-1-weiwan@google.com> Message-Id: <20201209005444.1949356-3-weiwan@google.com> Mime-Version: 1.0 References: <20201209005444.1949356-1-weiwan@google.com> X-Mailer: git-send-email 2.29.2.576.ga3fc446d84-goog Subject: [PATCH net-next v4 2/3] net: implement threaded-able napi poll loop support From: Wei Wang To: David Miller , netdev@vger.kernel.org, Jakub Kicinski Cc: Paolo Abeni , Hannes Frederic Sowa , Eric Dumazet , Felix Fietkau , Hillf Danton Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org This patch allows running each napi poll loop inside its own kernel thread. The threaded mode could be enabled through napi_set_threaded() api, and does not require a device up/down. The kthread gets created on demand when napi_set_threaded() is called, and gets shut down eventually in napi_disable(). Once that threaded mode is enabled and the kthread is started, napi_schedule() will wake-up such thread instead of scheduling the softirq. The threaded poll loop behaves quite likely the net_rx_action, but it does not have to manipulate local irqs and uses an explicit scheduling point based on netdev_budget. Co-developed-by: Paolo Abeni Signed-off-by: Paolo Abeni Co-developed-by: Hannes Frederic Sowa Signed-off-by: Hannes Frederic Sowa Co-developed-by: Jakub Kicinski Signed-off-by: Jakub Kicinski Signed-off-by: Wei Wang Reviewed-by: Eric Dumazet --- include/linux/netdevice.h | 5 ++ net/core/dev.c | 105 ++++++++++++++++++++++++++++++++++++++ 2 files changed, 110 insertions(+) diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h index 7bf167993c05..abd3b52b7da6 100644 --- a/include/linux/netdevice.h +++ b/include/linux/netdevice.h @@ -347,6 +347,7 @@ struct napi_struct { struct list_head dev_list; struct hlist_node napi_hash_node; unsigned int napi_id; + struct task_struct *thread; }; enum { @@ -358,6 +359,7 @@ enum { NAPI_STATE_NO_BUSY_POLL, /* Do not add in napi_hash, no busy polling */ NAPI_STATE_IN_BUSY_POLL, /* sk_busy_loop() owns this NAPI */ NAPI_STATE_PREFER_BUSY_POLL, /* prefer busy-polling over softirq processing*/ + NAPI_STATE_THREADED, /* The poll is performed inside its own thread*/ }; enum { @@ -369,6 +371,7 @@ enum { NAPIF_STATE_NO_BUSY_POLL = BIT(NAPI_STATE_NO_BUSY_POLL), NAPIF_STATE_IN_BUSY_POLL = BIT(NAPI_STATE_IN_BUSY_POLL), NAPIF_STATE_PREFER_BUSY_POLL = BIT(NAPI_STATE_PREFER_BUSY_POLL), + NAPIF_STATE_THREADED = BIT(NAPI_STATE_THREADED), }; enum gro_result { @@ -495,6 +498,8 @@ static inline bool napi_complete(struct napi_struct *n) return napi_complete_done(n, 0); } +int napi_set_threaded(struct napi_struct *n, bool threaded); + /** * napi_disable - prevent NAPI from scheduling * @n: NAPI context diff --git a/net/core/dev.c b/net/core/dev.c index 8064af1dd03c..cb6c4e2363a4 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -91,6 +91,7 @@ #include #include #include +#include #include #include #include @@ -1475,6 +1476,36 @@ void netdev_notify_peers(struct net_device *dev) } EXPORT_SYMBOL(netdev_notify_peers); +static int napi_threaded_poll(void *data); + +static int napi_kthread_create(struct napi_struct *n) +{ + int err = 0; + + /* Create and wake up the kthread once to put it in + * TASK_INTERRUPTIBLE mode to avoid the blocked task + * warning and work with loadavg. + */ + n->thread = kthread_run(napi_threaded_poll, n, "napi/%s-%d", + n->dev->name, n->napi_id); + if (IS_ERR(n->thread)) { + err = PTR_ERR(n->thread); + pr_err("kthread_run failed with err %d\n", err); + n->thread = NULL; + } + + return err; +} + +static void napi_kthread_stop(struct napi_struct *n) +{ + if (!n->thread) + return; + kthread_stop(n->thread); + clear_bit(NAPI_STATE_THREADED, &n->state); + n->thread = NULL; +} + static int __dev_open(struct net_device *dev, struct netlink_ext_ack *extack) { const struct net_device_ops *ops = dev->netdev_ops; @@ -4234,6 +4265,11 @@ int gro_normal_batch __read_mostly = 8; static inline void ____napi_schedule(struct softnet_data *sd, struct napi_struct *napi) { + if (test_bit(NAPI_STATE_THREADED, &napi->state)) { + wake_up_process(napi->thread); + return; + } + list_add_tail(&napi->poll_list, &sd->poll_list); __raise_softirq_irqoff(NET_RX_SOFTIRQ); } @@ -6690,6 +6726,29 @@ static void init_gro_hash(struct napi_struct *napi) napi->gro_bitmask = 0; } +int napi_set_threaded(struct napi_struct *n, bool threaded) +{ + int err = 0; + + ASSERT_RTNL(); + + if (threaded == !!test_bit(NAPI_STATE_THREADED, &n->state)) + return 0; + if (threaded) { + if (!n->thread) { + err = napi_kthread_create(n); + if (err) + goto out; + } + set_bit(NAPI_STATE_THREADED, &n->state); + } else { + clear_bit(NAPI_STATE_THREADED, &n->state); + } + +out: + return err; +} + void netif_napi_add(struct net_device *dev, struct napi_struct *napi, int (*poll)(struct napi_struct *, int), int weight) { @@ -6731,6 +6790,7 @@ void napi_disable(struct napi_struct *n) msleep(1); hrtimer_cancel(&n->timer); + napi_kthread_stop(n); clear_bit(NAPI_STATE_PREFER_BUSY_POLL, &n->state); clear_bit(NAPI_STATE_DISABLE, &n->state); @@ -6859,6 +6919,51 @@ static int napi_poll(struct napi_struct *n, struct list_head *repoll) return work; } +static int napi_thread_wait(struct napi_struct *napi) +{ + set_current_state(TASK_INTERRUPTIBLE); + + while (!kthread_should_stop() && !napi_disable_pending(napi)) { + if (test_bit(NAPI_STATE_SCHED, &napi->state)) { + WARN_ON(!list_empty(&napi->poll_list)); + __set_current_state(TASK_RUNNING); + return 0; + } + + schedule(); + set_current_state(TASK_INTERRUPTIBLE); + } + __set_current_state(TASK_RUNNING); + return -1; +} + +static int napi_threaded_poll(void *data) +{ + struct napi_struct *napi = data; + void *have; + + while (!napi_thread_wait(napi)) { + for (;;) { + bool repoll = false; + + local_bh_disable(); + + have = netpoll_poll_lock(napi); + __napi_poll(napi, &repoll); + netpoll_poll_unlock(have); + + __kfree_skb_flush(); + local_bh_enable(); + + if (!repoll) + break; + + cond_resched(); + } + } + return 0; +} + static __latent_entropy void net_rx_action(struct softirq_action *h) { struct softnet_data *sd = this_cpu_ptr(&softnet_data);