From: Eric Dumazet Date: Tue, 31 Aug 2010 07:40:16 +0000 (+0000) Subject: net: add a comment on netdev->last_rx X-Git-Url: http://git.lede-project.org./?a=commitdiff_plain;h=4dc89133f49b;p=openwrt%2Fstaging%2Fblogic.git net: add a comment on netdev->last_rx As some driver authors seem to reintroduce dev->last_rx use, add a comment to strongly discourage this. Since commit 6cf3f41e6c0 (bonding, net: Move last_rx update into bonding recv logic), network drivers dont need to update last_rx themselves, unless they use this field to implement a timeout. Not updating last_rx helps not dirtying a cache line, improving performance in SMP. Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller --- diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h index 0cf9448a32c4..c82220a9f3d5 100644 --- a/include/linux/netdevice.h +++ b/include/linux/netdevice.h @@ -953,7 +953,14 @@ struct net_device { /* * Cache line mostly used on receive path (including eth_type_trans()) */ - unsigned long last_rx; /* Time of last Rx */ + unsigned long last_rx; /* Time of last Rx + * This should not be set in + * drivers, unless really needed, + * because network stack (bonding) + * use it if/when necessary, to + * avoid dirtying this cache line. + */ + /* Interface address info used in eth_type_trans() */ unsigned char *dev_addr; /* hw address, (before bcast because most packets are