From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Dumazet Subject: [PATCH net-next-2.6] net: shrinks struct net_device Date: Thu, 16 Sep 2010 14:58:13 +0200 Message-ID: <1284641893.3352.25.camel@edumazet-laptop> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: netdev , Jiri Pirko To: David Miller Return-path: Received: from mail-bw0-f46.google.com ([209.85.214.46]:35434 "EHLO mail-bw0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753932Ab0IPM6T (ORCPT ); Thu, 16 Sep 2010 08:58:19 -0400 Received: by bwz11 with SMTP id 11so1537026bwz.19 for ; Thu, 16 Sep 2010 05:58:18 -0700 (PDT) Sender: netdev-owner@vger.kernel.org List-ID: commit ab95bfe01 (net: replace hooks in __netif_receive_skb) added rx_handler at wrong place, between two cache line aligned objects, creating a big hole (a full cache line) Move rx_handler and rx_handler_data before rx_queue, filling existing hole. Move master field in the cache line(s) used in receive path. This saves 64 bytes (or L1_CACHE_BYTES), and avoids two possible cache misses in receive path. Signed-off-by: Eric Dumazet --- include/linux/netdevice.h | 20 +++++++++++--------- 1 file changed, 11 insertions(+), 9 deletions(-) diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h index 8992fff..ec17887 100644 --- a/include/linux/netdevice.h +++ b/include/linux/netdevice.h @@ -918,10 +918,6 @@ struct net_device { unsigned short needed_headroom; unsigned short needed_tailroom; - struct net_device *master; /* Pointer to master device of a group, - * which this device is member of. - */ - /* Interface address info. */ unsigned char perm_addr[MAX_ADDR_LEN]; /* permanent hw address */ unsigned char addr_assign_type; /* hw address assignment type */ @@ -951,7 +947,7 @@ struct net_device { assign before registering */ /* - * Cache line mostly used on receive path (including eth_type_trans()) + * Cache lines mostly used on receive path (including eth_type_trans()) */ unsigned long last_rx; /* Time of last Rx * This should not be set in @@ -961,6 +957,10 @@ struct net_device { * avoid dirtying this cache line. */ + struct net_device *master; /* Pointer to master device of a group, + * which this device is member of. + */ + /* Interface address info used in eth_type_trans() */ unsigned char *dev_addr; /* hw address, (before bcast because most packets are @@ -980,10 +980,14 @@ struct net_device { unsigned int num_rx_queues; #endif - struct netdev_queue rx_queue; rx_handler_func_t *rx_handler; void *rx_handler_data; + struct netdev_queue rx_queue; /* use two cache lines */ + +/* + * Cache lines mostly used on transmit path + */ struct netdev_queue *_tx ____cacheline_aligned_in_smp; /* Number of TX queues allocated at alloc_netdev_mq() time */ @@ -997,9 +1001,7 @@ struct net_device { unsigned long tx_queue_len; /* Max frames per queue allowed */ spinlock_t tx_global_lock; -/* - * One part is mostly used on xmit path (device) - */ + /* These may be needed for future network-power-down code. */ /*