From patchwork Wed Jan 20 03:34:54 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Wei Wang X-Patchwork-Id: 367676 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=-26.3 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 947F0C433DB for ; Wed, 20 Jan 2021 03:39:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5ABAF2310D for ; Wed, 20 Jan 2021 03:39:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729362AbhATDhk (ORCPT ); Tue, 19 Jan 2021 22:37:40 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53446 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729913AbhATDfl (ORCPT ); Tue, 19 Jan 2021 22:35:41 -0500 Received: from mail-qt1-x849.google.com (mail-qt1-x849.google.com [IPv6:2607:f8b0:4864:20::849]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 84A38C0613C1 for ; Tue, 19 Jan 2021 19:35:01 -0800 (PST) Received: by mail-qt1-x849.google.com with SMTP id w3so20056151qti.17 for ; Tue, 19 Jan 2021 19:35:01 -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=XDlapyM+7BgJ9DMCUCwjp4KkPFgyLD0ktpAqmgX2S/g=; b=KLA96Gi+VaamLrxS0NOv9/xpxkt+dsHswxFNz/xnR8ZKV4PqSJgqMnAZyuqkgeqYEa j2RSIqyYXV/eCARDuNw+BK/O4KB6mPUC5XcdSK+lEFFYGslJ8JmbzfSNvES+dwqntHSM t0uCjHQ2QvCJSJfUnfI9MZMAyED57SivsQlxrVceIKd+GUPU1hbMXKX5YvKH8PMxX+ld W/cF5stMCNPnL53Pw4/6BEDUUkGZXlYdOYWfBI8qYAasicAJUyK1VzaD/ni5wJO9uYqJ NCgi5ElwUlf7wWKe+RZCj+vU108uZZqo8FrzeDwFxVcoEtB06ciMHIJfdb7Ccsf8NBjX r9JQ== 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=XDlapyM+7BgJ9DMCUCwjp4KkPFgyLD0ktpAqmgX2S/g=; b=LmK55GG5SzOWvRPjZRz/pPV+7wH8b1Myoxps7wndgKmwDRdHTZU1U6WGo+oq9sn+EN tuXcHqOa9B2zwdrpjIdCkbOhSepwJ/h+DbN/imzU30X/PaMSrZQo62Jzul5Q9Z4dJO3T G0oiwtMd2c9B2Fed99qZCy68z2kSHxqgRp0P+aw15Kqunxh8i3WUltJeVivFF/77A2Pu +iI0wnLmMzqjeg0alahdG+Getbkdr0pbzIVvr+FGXguIFm8K79vumNQ4gOPE3/TRTTO2 buRIZNNFYmQxzwLreg6ifqaEv4OLuS0UMoZsji5oYKOis7Q49Ef4b+pjaAc4x5kgmw0j NPMw== X-Gm-Message-State: AOAM530koEfXz8uqJjR8WCDBTah2KAhCtlzY7MsZgSQ3l9itptbslbZX sayveKkg0Ih2poUdRCD+0FNMp5AyJcs= X-Google-Smtp-Source: ABdhPJwlmV/8rqhWWVlUjQK5C7mPqkXbuXpXI1sH3/urgS3NZ4WI9JtNlSCJiaX0buoFfcecmWBubWmRPMw= 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:ba18:: with SMTP id w24mr3978420qvf.57.1611113700708; Tue, 19 Jan 2021 19:35:00 -0800 (PST) Date: Tue, 19 Jan 2021 19:34:54 -0800 In-Reply-To: <20210120033455.4034611-1-weiwan@google.com> Message-Id: <20210120033455.4034611-3-weiwan@google.com> Mime-Version: 1.0 References: <20210120033455.4034611-1-weiwan@google.com> X-Mailer: git-send-email 2.30.0.284.gd98b1dd5eaa7-goog Subject: [PATCH net-next v7 2/3] net: implement threaded-able napi poll loop support From: Wei Wang To: David Miller , netdev@vger.kernel.org, Jakub Kicinski Cc: Eric Dumazet , Paolo Abeni , Hannes Frederic Sowa , Felix Fietkau , Alexander Duyck 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 napi->weight. 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 --- include/linux/netdevice.h | 19 ++---- net/core/dev.c | 137 ++++++++++++++++++++++++++++++++++++++ 2 files changed, 142 insertions(+), 14 deletions(-) diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h index 02dcef4d66e2..8cb8d43ea5fa 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 { @@ -503,20 +506,7 @@ static inline bool napi_complete(struct napi_struct *n) */ void napi_disable(struct napi_struct *n); -/** - * napi_enable - enable NAPI scheduling - * @n: NAPI context - * - * Resume NAPI from being scheduled on this context. - * Must be paired with napi_disable. - */ -static inline void napi_enable(struct napi_struct *n) -{ - BUG_ON(!test_bit(NAPI_STATE_SCHED, &n->state)); - smp_mb__before_atomic(); - clear_bit(NAPI_STATE_SCHED, &n->state); - clear_bit(NAPI_STATE_NPSVC, &n->state); -} +void napi_enable(struct napi_struct *n); /** * napi_synchronize - wait until NAPI is not running @@ -2143,6 +2133,7 @@ struct net_device { struct lock_class_key *qdisc_running_key; bool proto_down; unsigned wol_enabled:1; + unsigned threaded:1; struct list_head net_notifier_list; diff --git a/net/core/dev.c b/net/core/dev.c index 7d23bff03864..7ffa91475856 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -91,6 +91,7 @@ #include #include #include +#include #include #include #include @@ -1493,6 +1494,37 @@ 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; @@ -4252,6 +4284,21 @@ int gro_normal_batch __read_mostly = 8; static inline void ____napi_schedule(struct softnet_data *sd, struct napi_struct *napi) { + struct task_struct *thread; + + if (test_bit(NAPI_STATE_THREADED, &napi->state)) { + /* Paired with smp_mb__before_atomic() in + * napi_set_threaded(). Use READ_ONCE() to guarantee + * a complete read on napi->thread. Only call + * wake_up_process() when it's not NULL. + */ + thread = READ_ONCE(napi->thread); + if (thread) { + wake_up_process(thread); + return; + } + } + list_add_tail(&napi->poll_list, &sd->poll_list); __raise_softirq_irqoff(NET_RX_SOFTIRQ); } @@ -6693,6 +6740,33 @@ static void init_gro_hash(struct napi_struct *napi) napi->gro_bitmask = 0; } +static int napi_set_threaded(struct napi_struct *n, bool threaded) +{ + int err = 0; + + if (threaded == !!test_bit(NAPI_STATE_THREADED, &n->state)) + return 0; + + if (!threaded) { + clear_bit(NAPI_STATE_THREADED, &n->state); + return 0; + } + + if (!n->thread) { + err = napi_kthread_create(n); + if (err) + return err; + } + + /* Make sure kthread is created before THREADED bit + * is set. + */ + smp_mb__before_atomic(); + set_bit(NAPI_STATE_THREADED, &n->state); + + return 0; +} + void netif_napi_add(struct net_device *dev, struct napi_struct *napi, int (*poll)(struct napi_struct *, int), int weight) { @@ -6734,12 +6808,30 @@ 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); } EXPORT_SYMBOL(napi_disable); +/** + * napi_enable - enable NAPI scheduling + * @n: NAPI context + * + * Resume NAPI from being scheduled on this context. + * Must be paired with napi_disable. + */ +void napi_enable(struct napi_struct *n) +{ + BUG_ON(!test_bit(NAPI_STATE_SCHED, &n->state)); + WARN_ON(napi_set_threaded(n, n->dev->threaded)); + smp_mb__before_atomic(); + clear_bit(NAPI_STATE_SCHED, &n->state); + clear_bit(NAPI_STATE_NPSVC, &n->state); +} +EXPORT_SYMBOL(napi_enable); + static void flush_gro_hash(struct napi_struct *napi) { int i; @@ -6862,6 +6954,51 @@ 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);