netdev - Re: BUG: unable to handle kernel paging request at 000041ed00000001

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Message-Id: <80C864F3-B075-4E3A-B72E-6FCD945A8058@res.lt>
Date:	Mon, 14 Jun 2010 10:05:30 +0300
From:	Arturas <arturasl@....lt>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	netdev@...r.kernel.org
Subject: Re: BUG: unable to handle kernel paging request at 000041ed00000001

Hi,

your patch fixes hangs and i get a warning (see bellow if needed) when it triggers. 
As I understand it is workaround and a real fix should be different? 
What about bonding to be multiqueue aware?

I also have another issue with NMI. On older machine with 5500 xeons i 
have almost no overhead with nmi_watchdog enabled, but on this it is about twice.
without nmi enabled cpu peak average is 30%, and with nmi enabled i have 53%.
When traffic is not passing all cpus are idling at 100%.
Maybe overhead could be a little bit smaller? :-)

[ 8064.562106] WARNING: at net/core/dev.c:1964 dev_queue_xmit+0x504/0x520()
[ 8064.562108] Hardware name: S5520UR
[ 8064.562108] br0
[ 8064.562109] Modules linked in: ipt_REDIRECT xt_tcpudp ipt_set iptable_filter iptable_nat nf_nat ipt_addrtype xt_dscp xt_string xt_owner xt_multiport xt_mark xt_iprange xt_hashlimit xt_conntrack xt_connmark xt_DSCP xt_NFQUEUE xt_MARK xt_CONNMARK ip_tables x_tables ip_set_ipmap ip_set cls_u32 sch_htb ipmi_watchdog ipmi_devintf ipmi_si ipmi_msghandler nf_conntrack_ipv4 nf_defrag_ipv4 nf_conntrack bonding ipv6 ixgbe igb mdio
[ 8064.562125] Pid: 8643, comm: lighttpd Not tainted 2.6.34-gentoo #6
[ 8064.562126] Call Trace:
[ 8064.562133]  [<ffffffff8103e463>] ? warn_slowpath_common+0x73/0xb0
[ 8064.562135]  [<ffffffff8103e500>] ? warn_slowpath_fmt+0x40/0x50
[ 8064.562137]  [<ffffffff812f47b4>] ? dev_queue_xmit+0x504/0x520
[ 8064.562141]  [<ffffffff813222d2>] ? ip_queue_xmit+0x182/0x3e0
[ 8064.562145]  [<ffffffff81335c1e>] ? tcp_init_tso_segs+0x2e/0x50
[ 8064.562147]  [<ffffffff81338bb5>] ? tcp_write_xmit+0x75/0xa00
[ 8064.562151]  [<ffffffff810494f3>] ? lock_timer_base+0x33/0x70
[ 8064.562153]  [<ffffffff8133665c>] ? tcp_transmit_skb+0x3ac/0x820
[ 8064.562155]  [<ffffffff8132bd76>] ? tcp_sendmsg+0x866/0xbf0
[ 8064.562156]  [<ffffffff81338d2c>] ? tcp_write_xmit+0x1ec/0xa00
[ 8064.562161]  [<ffffffff812e5f7d>] ? lock_sock_nested+0x3d/0xe0
[ 8064.562163]  [<ffffffff812e0ff0>] ? sock_aio_write+0x0/0x150
[ 8064.562166]  [<ffffffff81339599>] ? __tcp_push_pending_frames+0x19/0x80
[ 8064.562167]  [<ffffffff8132a3fa>] ? do_tcp_setsockopt+0x53a/0x690
[ 8064.562171]  [<ffffffff810bc439>] ? do_sync_readv_writev+0xa9/0xf0
[ 8064.562173]  [<ffffffff810494f3>] ? lock_timer_base+0x33/0x70
[ 8064.562174]  [<ffffffff810bc63f>] ? do_sync_read+0xbf/0x100
[ 8064.562176]  [<ffffffff810bcb82>] ? do_readv_writev+0x172/0x220
[ 8064.562179]  [<ffffffff810cdc3f>] ? d_kill+0x5f/0x80
[ 8064.562181]  [<ffffffff810ce3f8>] ? dput+0xb8/0x180
[ 8064.562183]  [<ffffffff812e1ef2>] ? sockfd_lookup_light+0x22/0x80
[ 8064.562185]  [<ffffffff812e248d>] ? sys_setsockopt+0x6d/0xd0
[ 8064.562188]  [<ffffffff81002502>] ? system_call_fastpath+0x16/0x1b


On Jun 10, 2010, at 7:00 PM, Eric Dumazet wrote:

> Le jeudi 10 juin 2010 à 16:45 +0300, Arturas a écrit :
> 
> This is right mailing list :)
> 
> I would try following patch for 2.6.34,
> not blindly trusting sk_tx_queue_get(sk)
> 
> --- net/core/dev.c.orig	2010-06-10 17:52:17.000000000 +0200
> +++ net/core/dev.c	2010-06-10 17:54:56.000000000 +0200
> @@ -1958,12 +1958,10 @@
> static inline u16 dev_cap_txqueue(struct net_device *dev, u16 queue_index)
> {
> 	if (unlikely(queue_index >= dev->real_num_tx_queues)) {
> -		if (net_ratelimit()) {
> -			WARN(1, "%s selects TX queue %d, but "
> -			     "real number of TX queues is %d\n",
> -			     dev->name, queue_index,
> -			     dev->real_num_tx_queues);
> -		}
> +		WARN_ONCE("%s selects TX queue %d, but "
> +			  "real number of TX queues is %d\n",
> +			  dev->name, queue_index,
> +			  dev->real_num_tx_queues);
> 		return 0;
> 	}
> 	return queue_index;
> @@ -1977,6 +1975,7 @@
> 
> 	if (sk_tx_queue_recorded(sk)) {
> 		queue_index = sk_tx_queue_get(sk);
> +		queue_index = dev_cap_txqueue(dev, queue_index);
> 	} else {
> 		const struct net_device_ops *ops = dev->netdev_ops;
> 
> 
> 

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