From patchwork Tue Jan 26 17:39:39 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jesper Dangaard Brouer X-Patchwork-Id: 372225 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=-16.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER, INCLUDES_PATCH, MAILING_LIST_MULTI, SPF_HELO_NONE, SPF_PASS 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 A3F5FC433E0 for ; Wed, 27 Jan 2021 10:16:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5F8292072C for ; Wed, 27 Jan 2021 10:16:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S314317AbhAZXE4 (ORCPT ); Tue, 26 Jan 2021 18:04:56 -0500 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:23017 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2392968AbhAZRlS (ORCPT ); Tue, 26 Jan 2021 12:41:18 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1611682791; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding; bh=IFp7XUFQoexvLrbCvUTVH11jM+Rk85sANRL4Qy6Bv6Q=; b=drSC6w2eQ5kSry2exq7fxyMyXlvFNXRrX1gaAaprY0VwogFZ38C6t2Qe+uuL/lADIbndy0 iHvBcyTK3yWx2i0AX/DsqT+kcSDxYX6M823rXFv3Jtch8L8qaoJDOEpjglGFKx0HjY9pif 574lppL6E5Zrwu+mh2tx8pLyfm8XRhU= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-117-hxHZCvQ3PWikHu4CPHGlfQ-1; Tue, 26 Jan 2021 12:39:46 -0500 X-MC-Unique: hxHZCvQ3PWikHu4CPHGlfQ-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id A37241922963; Tue, 26 Jan 2021 17:39:44 +0000 (UTC) Received: from firesoul.localdomain (unknown [10.40.208.19]) by smtp.corp.redhat.com (Postfix) with ESMTP id 2A01C6B8D4; Tue, 26 Jan 2021 17:39:41 +0000 (UTC) Received: from [192.168.42.3] (localhost [IPv6:::1]) by firesoul.localdomain (Postfix) with ESMTP id E1AF93217DA48; Tue, 26 Jan 2021 18:39:39 +0100 (CET) Subject: [PATCH net-next V1] net: adjust net_device layout for cacheline usage From: Jesper Dangaard Brouer To: David Ahern , netdev@vger.kernel.org, Jakub Kicinski , "David S. Miller" Cc: Jesper Dangaard Brouer , bpf@vger.kernel.org, Eric Dumazet , Daniel Borkmann , Alexei Starovoitov Date: Tue, 26 Jan 2021 18:39:39 +0100 Message-ID: <161168277983.410784.12401225493601624417.stgit@firesoul> User-Agent: StGit/0.19 MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org The current layout of net_device is not optimal for cacheline usage. The member adj_list.lower linked list is split between cacheline 2 and 3. The ifindex is placed together with stats (struct net_device_stats), although most modern drivers don't update this stats member. The members netdev_ops, mtu and hard_header_len are placed on three different cachelines. These members are accessed for XDP redirect into devmap, which were noticeably with perf tool. When not using the map redirect variant (like TC-BPF does), then ifindex is also used, which is placed on a separate fourth cacheline. These members are also accessed during forwarding with regular network stack. The members priv_flags and flags are on fast-path for network stack transmit path in __dev_queue_xmit (currently located together with mtu cacheline). This patch creates a read mostly cacheline, with the purpose of keeping the above mentioned members on the same cacheline. Some netdev_features_t members also becomes part of this cacheline, which is on purpose, as function netif_skb_features() is on fast-path via validate_xmit_skb(). Signed-off-by: Jesper Dangaard Brouer --- include/linux/netdevice.h | 53 +++++++++++++++++++++++---------------------- 1 file changed, 27 insertions(+), 26 deletions(-) diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h index b7915484369c..2645f114de54 100644 --- a/include/linux/netdevice.h +++ b/include/linux/netdevice.h @@ -1855,7 +1855,6 @@ struct net_device { unsigned long mem_end; unsigned long mem_start; unsigned long base_addr; - int irq; /* * Some hardware also needs these fields (state,dev_list, @@ -1877,6 +1876,23 @@ struct net_device { struct list_head lower; } adj_list; + /* Read-mostly cache-line for fast-path access */ + unsigned int flags; + unsigned int priv_flags; + const struct net_device_ops *netdev_ops; + int ifindex; + unsigned short gflags; + unsigned short hard_header_len; + + /* Note : dev->mtu is often read without holding a lock. + * Writers usually hold RTNL. + * It is recommended to use READ_ONCE() to annotate the reads, + * and to use WRITE_ONCE() to annotate the writes. + */ + unsigned int mtu; + unsigned short needed_headroom; + unsigned short needed_tailroom; + netdev_features_t features; netdev_features_t hw_features; netdev_features_t wanted_features; @@ -1885,10 +1901,15 @@ struct net_device { netdev_features_t mpls_features; netdev_features_t gso_partial_features; - int ifindex; + unsigned int min_mtu; + unsigned int max_mtu; + unsigned short type; + unsigned char min_header_len; + unsigned char name_assign_type; + int group; - struct net_device_stats stats; + struct net_device_stats stats; /* not used by modern drivers */ atomic_long_t rx_dropped; atomic_long_t tx_dropped; @@ -1902,7 +1923,6 @@ struct net_device { const struct iw_handler_def *wireless_handlers; struct iw_public_data *wireless_data; #endif - const struct net_device_ops *netdev_ops; const struct ethtool_ops *ethtool_ops; #ifdef CONFIG_NET_L3_MASTER_DEV const struct l3mdev_ops *l3mdev_ops; @@ -1921,34 +1941,12 @@ struct net_device { const struct header_ops *header_ops; - unsigned int flags; - unsigned int priv_flags; - - unsigned short gflags; - unsigned short padded; - unsigned char operstate; unsigned char link_mode; unsigned char if_port; unsigned char dma; - /* Note : dev->mtu is often read without holding a lock. - * Writers usually hold RTNL. - * It is recommended to use READ_ONCE() to annotate the reads, - * and to use WRITE_ONCE() to annotate the writes. - */ - unsigned int mtu; - unsigned int min_mtu; - unsigned int max_mtu; - unsigned short type; - unsigned short hard_header_len; - unsigned char min_header_len; - unsigned char name_assign_type; - - unsigned short needed_headroom; - unsigned short needed_tailroom; - /* Interface address info. */ unsigned char perm_addr[MAX_ADDR_LEN]; unsigned char addr_assign_type; @@ -1959,7 +1957,10 @@ struct net_device { unsigned short neigh_priv_len; unsigned short dev_id; unsigned short dev_port; + unsigned short padded; + spinlock_t addr_list_lock; + int irq; struct netdev_hw_addr_list uc; struct netdev_hw_addr_list mc;