From mboxrd@z Thu Jan 1 00:00:00 1970 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=-12.4 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 96242C433E0 for ; Wed, 29 Jul 2020 17:44:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 734C020809 for ; Wed, 29 Jul 2020 17:44:09 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="ZhUPAQ0/" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727001AbgG2RoI (ORCPT ); Wed, 29 Jul 2020 13:44:08 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33400 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726533AbgG2RoI (ORCPT ); Wed, 29 Jul 2020 13:44:08 -0400 Received: from mail-pj1-x1043.google.com (mail-pj1-x1043.google.com [IPv6:2607:f8b0:4864:20::1043]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0209EC061794 for ; Wed, 29 Jul 2020 10:44:08 -0700 (PDT) Received: by mail-pj1-x1043.google.com with SMTP id k71so2219995pje.0 for ; Wed, 29 Jul 2020 10:44:07 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=subject:to:cc:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=UXpbThgoPFMCxaKk+VBIYo315ccTQKqksdF40uLodTU=; b=ZhUPAQ0/pgkB2JzMg0WflUcwiw3qKy0QfewBV1RjpdDZ6lduKOcqCoPVxrYRAf1jau bjY3gRMGVe5DDgGdoJRUgZhCVguJfUPAP0vsKb780ReVHkiBz/zvlZAKIcyr8/lmbcx2 c0ytvt7mYAjL5e+XDTUtp+jAOyOiVzY7+smmtrXzNPsMJKbo8rbNAdZVh6c4/BkUExr4 ttq+1Zv309PPqDQa6Q6GHaGlGUnRS/2wL2gpF8M//dG3ivJpDYIue8R2xlj6U+LyzVjH ZIuIDIGx6QFSHR61nMiA7KCD3WK8ZNwdPYBg49nWLzRxOFZe8scDtEn0a+CFrrm9jdrt bQEg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=UXpbThgoPFMCxaKk+VBIYo315ccTQKqksdF40uLodTU=; b=se4+11sBLrneuL5iAaNFoGYelMu3D9ue9VcOcUNGB5V4pIbsnUY4tt+zOPV3Sk0Lg7 oqrAcdq4h95tLKCNhwr+HncRPC5nCdmxA30fXlxUrfVLCQww3EFkwabD6f75uK8xlumJ OJNVlGmHABtLIgiUwgxCSu09dzbyUuZF06igeflhP/+OqwHAdDt5HSxi7EPxHk8wi9Jg 1ROW86qg+I/X/z7vL+7Ydt3OmO2Q/t9hKOIz1ED3PQZNeg5rmRBTe8uNrtWUP9mPOMtr tRZh4dmH0BXO3rB32U0saxwVAF0aU1cllG99n2CitcLsZHIHazHoBDac+9qOCuJWagwz K8PQ== X-Gm-Message-State: AOAM532RNzQ7ZP5FttvXUVmz5EsXUygesQtjvayryYxmR4j78rLIYsam RXtmACLR0HydujDH0PKtlP8= X-Google-Smtp-Source: ABdhPJwIGYuzmgrJOQ27NbEukkm+iR5MpfDBmrJtgmZa/IaZn1zROiXSe2WNGb+h2fD2YlNFM79UUA== X-Received: by 2002:a17:90a:c398:: with SMTP id h24mr10784453pjt.211.1596044647469; Wed, 29 Jul 2020 10:44:07 -0700 (PDT) Received: from [10.1.10.11] (c-73-241-150-58.hsd1.ca.comcast.net. [73.241.150.58]) by smtp.gmail.com with ESMTPSA id b13sm3020828pjl.7.2020.07.29.10.44.05 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 29 Jul 2020 10:44:06 -0700 (PDT) Subject: Re: [PATCH] net: add support for threaded NAPI polling To: Felix Fietkau , netdev@vger.kernel.org Cc: Eric Dumazet , Hillf Danton References: <20200729165058.83984-1-nbd@nbd.name> From: Eric Dumazet Message-ID: <866c7d83-868d-120e-f535-926c4cc9e615@gmail.com> Date: Wed, 29 Jul 2020 10:44:04 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.9.0 MIME-Version: 1.0 In-Reply-To: <20200729165058.83984-1-nbd@nbd.name> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On 7/29/20 9:50 AM, Felix Fietkau wrote: > For some drivers (especially 802.11 drivers), doing a lot of work in the NAPI > poll function does not perform well. Since NAPI poll is bound to the CPU it > was scheduled from, we can easily end up with a few very busy CPUs spending > most of their time in softirq/ksoftirqd and some idle ones. > > Introduce threaded NAPI for such drivers based on a workqueue. The API is the > same except for using netif_threaded_napi_add instead of netif_napi_add. > > In my tests with mt76 on MT7621 using threaded NAPI + a thread for tx scheduling > improves LAN->WLAN bridging throughput by 10-50%. Throughput without threaded > NAPI is wildly inconsistent, depending on the CPU that runs the tx scheduling > thread. > > With threaded NAPI, throughput seems stable and consistent (and higher than > the best results I got without it). > > Based on a patch by Hillf Danton > > Cc: Hillf Danton > Signed-off-by: Felix Fietkau > --- > Changes since RFC v2: > - fix unused but set variable reported by kbuild test robot > > Changes since RFC: > - disable softirq around threaded poll functions > - reuse most parts of napi_poll() > - fix re-schedule condition > > include/linux/netdevice.h | 23 ++++++ > net/core/dev.c | 162 ++++++++++++++++++++++++++------------ > 2 files changed, 133 insertions(+), 52 deletions(-) > > diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h > index ac2cd3f49aba..3a39211c7598 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 work_struct work; > }; > > enum { > @@ -357,6 +358,7 @@ enum { > NAPI_STATE_HASHED, /* In NAPI hash (busy polling possible) */ > 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_THREADED, /* Use threaded NAPI */ > }; > > enum { > @@ -367,6 +369,7 @@ enum { > NAPIF_STATE_HASHED = BIT(NAPI_STATE_HASHED), > NAPIF_STATE_NO_BUSY_POLL = BIT(NAPI_STATE_NO_BUSY_POLL), > NAPIF_STATE_IN_BUSY_POLL = BIT(NAPI_STATE_IN_BUSY_POLL), > + NAPIF_STATE_THREADED = BIT(NAPI_STATE_THREADED), > }; > > enum gro_result { > @@ -2315,6 +2318,26 @@ static inline void *netdev_priv(const struct net_device *dev) > void netif_napi_add(struct net_device *dev, struct napi_struct *napi, > int (*poll)(struct napi_struct *, int), int weight); > > +/** > + * netif_threaded_napi_add - initialize a NAPI context > + * @dev: network device > + * @napi: NAPI context > + * @poll: polling function > + * @weight: default weight > + * > + * This variant of netif_napi_add() should be used from drivers using NAPI > + * with CPU intensive poll functions. > + * This will schedule polling from a high priority workqueue that > + */ > +static inline void netif_threaded_napi_add(struct net_device *dev, > + struct napi_struct *napi, > + int (*poll)(struct napi_struct *, int), > + int weight) > +{ > + set_bit(NAPI_STATE_THREADED, &napi->state); > + netif_napi_add(dev, napi, poll, weight); > +} > + > /** > * netif_tx_napi_add - initialize a NAPI context > * @dev: network device > diff --git a/net/core/dev.c b/net/core/dev.c > index 19f1abc26fcd..11b027f3a2b9 100644 > --- a/net/core/dev.c > +++ b/net/core/dev.c > @@ -158,6 +158,7 @@ static DEFINE_SPINLOCK(offload_lock); > struct list_head ptype_base[PTYPE_HASH_SIZE] __read_mostly; > struct list_head ptype_all __read_mostly; /* Taps */ > static struct list_head offload_base __read_mostly; > +static struct workqueue_struct *napi_workq __read_mostly; > > static int netif_rx_internal(struct sk_buff *skb); > static int call_netdevice_notifiers_info(unsigned long val, > @@ -6286,6 +6287,11 @@ void __napi_schedule(struct napi_struct *n) > { > unsigned long flags; > > + if (test_bit(NAPI_STATE_THREADED, &n->state)) { > + queue_work(napi_workq, &n->work); > + return; > + } > + Where is the corresponding cancel_work_sync() or flush_work() at device dismantle ? Just hoping the thread will eventually run seems optimistic to me. Quite frankly, I do believe this STATE_THREADED status should be a generic NAPI attribute that can be changed dynamically, at admin request, instead of having to change/recompile a driver.