From patchwork Sun Jul 26 16:31:19 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Felix Fietkau X-Patchwork-Id: 1336520 X-Patchwork-Delegate: davem@davemloft.net Return-Path: X-Original-To: patchwork-incoming-netdev@ozlabs.org Delivered-To: patchwork-incoming-netdev@ozlabs.org Authentication-Results: ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=vger.kernel.org (client-ip=23.128.96.18; helo=vger.kernel.org; envelope-from=netdev-owner@vger.kernel.org; receiver=) Authentication-Results: ozlabs.org; dmarc=none (p=none dis=none) header.from=nbd.name Authentication-Results: ozlabs.org; dkim=fail reason="signature verification failed" (1024-bit key; unprotected) header.d=nbd.name header.i=@nbd.name header.a=rsa-sha256 header.s=20160729 header.b=WvIMglHv; dkim-atps=neutral Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by ozlabs.org (Postfix) with ESMTP id 4BF7jn3R3Dz9sRN for ; Mon, 27 Jul 2020 02:31:25 +1000 (AEST) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726764AbgGZQbX (ORCPT ); Sun, 26 Jul 2020 12:31:23 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60902 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726044AbgGZQbX (ORCPT ); Sun, 26 Jul 2020 12:31:23 -0400 Received: from nbd.name (nbd.name [IPv6:2a01:4f8:221:3d45::2]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 022D5C0619D2 for ; Sun, 26 Jul 2020 09:31:23 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=nbd.name; s=20160729; h=Content-Transfer-Encoding:MIME-Version:Message-Id:Date:Subject :Cc:To:From:Sender:Reply-To:Content-Type:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: In-Reply-To:References:List-Id:List-Help:List-Unsubscribe:List-Subscribe: List-Post:List-Owner:List-Archive; bh=gOfY+L5m2gFYslw0Ou6nm2kKKDODYfGn/uBMSoHPHso=; b=WvIMglHvuXtYR18ZUTTg6broVH N5byepmCCDdUHqw3xf17uLL6DJqfYTChl7yday7EhTLe2ytVlSE9iCE9c5Jn1R2aBkUBYVtcvK555 sSKXxAzx4XvhTbvhx1s6b4EXh41vbQKXVjkR8hLMV+XIoKcEX8tii3dBSYPvFMZ7oDKY=; Received: from p5b206d80.dip0.t-ipconnect.de ([91.32.109.128] helo=localhost.localdomain) by ds12 with esmtpsa (TLS1.2:ECDHE_RSA_AES_128_CBC_SHA1:128) (Exim 4.89) (envelope-from ) id 1jzjYX-0003QO-1e; Sun, 26 Jul 2020 18:31:21 +0200 From: Felix Fietkau To: netdev@vger.kernel.org Cc: Hillf Danton Subject: [RFC] net: add support for threaded NAPI polling Date: Sun, 26 Jul 2020 18:31:19 +0200 Message-Id: <20200726163119.86162-1-nbd@nbd.name> X-Mailer: git-send-email 2.24.0 MIME-Version: 1.0 Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org 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 --- include/linux/netdevice.h | 23 ++++++++++++++++++++++ net/core/dev.c | 40 +++++++++++++++++++++++++++++++++++++++ 2 files changed, 63 insertions(+) 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..e140b6a9d5eb 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; + } + local_irq_save(flags); ____napi_schedule(this_cpu_ptr(&softnet_data), n); local_irq_restore(flags); @@ -6333,6 +6339,11 @@ EXPORT_SYMBOL(napi_schedule_prep); */ void __napi_schedule_irqoff(struct napi_struct *n) { + if (test_bit(NAPI_STATE_THREADED, &n->state)) { + queue_work(napi_workq, &n->work); + return; + } + ____napi_schedule(this_cpu_ptr(&softnet_data), n); } EXPORT_SYMBOL(__napi_schedule_irqoff); @@ -6601,6 +6612,30 @@ static void init_gro_hash(struct napi_struct *napi) napi->gro_bitmask = 0; } +static void napi_workfn(struct work_struct *work) +{ + struct napi_struct *n = container_of(work, struct napi_struct, work); + + for (;;) { + if (!test_bit(NAPI_STATE_SCHED, &n->state)) + return; + + if (n->poll(n, n->weight) < n->weight) + return; + + if (!need_resched()) + continue; + + /* + * have to pay for the latency of task switch even if + * napi is scheduled + */ + if (test_bit(NAPI_STATE_SCHED, &n->state)) + queue_work(napi_workq, work); + return; + } +} + void netif_napi_add(struct net_device *dev, struct napi_struct *napi, int (*poll)(struct napi_struct *, int), int weight) { @@ -6621,6 +6656,7 @@ void netif_napi_add(struct net_device *dev, struct napi_struct *napi, #ifdef CONFIG_NETPOLL napi->poll_owner = -1; #endif + INIT_WORK(&napi->work, napi_workfn); set_bit(NAPI_STATE_SCHED, &napi->state); napi_hash_add(napi); } @@ -10676,6 +10712,10 @@ static int __init net_dev_init(void) sd->backlog.weight = weight_p; } + napi_workq = alloc_workqueue("napi_workq", WQ_UNBOUND | WQ_HIGHPRI, + WQ_UNBOUND_MAX_ACTIVE); + BUG_ON(!napi_workq); + dev_boot_phase = 0; /* The loopback device is special if any other network devices