3

veth虚拟网络设备的qdisc

 3 years ago
source link: http://abcdxyzk.github.io/blog/2020/05/22/kernel-qdisc-veth/
Go to the source link to view the article. You can view the picture content, updated content and better typesetting reading experience. If the link is broken, please click the button below to view the snapshot at that time.
neoserver,ios ssh client

veth虚拟网络设备的qdisc

2020-05-22 11:24:00

http://hustcat.github.io/veth/

http://hustcat.github.io/vlan-performance-problem/

veth设备qdisc队列，而环回设备/桥接设备是没qdisc队列的，参考br_dev_setup函数。

在注册（创建）设备时，qdisc设置为noop_qdisc， register_netdevice -> dev_init_scheduler

void dev_init_scheduler(struct net_device *dev)
{
	dev->qdisc = &noop_qdisc;
	netdev_for_each_tx_queue(dev, dev_init_scheduler_queue, &noop_qdisc);
	dev_init_scheduler_queue(dev, &dev->rx_queue, &noop_qdisc);

	setup_timer(&dev->watchdog_timer, dev_watchdog, (unsigned long)dev);
}

打开设备时，如果没有配置qdisc时，就指定为默认的pfifo_fast队列： dev_open -> dev_activate，

void dev_activate(struct net_device *dev)
{
	int need_watchdog;

	/* No queueing discipline is attached to device;
	   create default one i.e. pfifo_fast for devices,
	   which need queueing and noqueue_qdisc for
	   virtual interfaces
	 */

	if (dev->qdisc == &noop_qdisc)
		attach_default_qdiscs(dev);
...
}

static void attach_default_qdiscs(struct net_device *dev)
{
	struct netdev_queue *txq;
	struct Qdisc *qdisc;

	txq = netdev_get_tx_queue(dev, 0);

	if (!netif_is_multiqueue(dev) || dev->tx_queue_len == 0) {
		netdev_for_each_tx_queue(dev, attach_one_default_qdisc, NULL);
		dev->qdisc = txq->qdisc_sleeping;
		atomic_inc(&dev->qdisc->refcnt);
	} else {///multi queue
		qdisc = qdisc_create_dflt(dev, txq, &mq_qdisc_ops, TC_H_ROOT);
		if (qdisc) {
			qdisc->ops->attach(qdisc);
			dev->qdisc = qdisc;
		}
	}
}

static void attach_one_default_qdisc(struct net_device *dev,
				     struct netdev_queue *dev_queue,
				     void *_unused)
{
	struct Qdisc *qdisc;

	if (dev->tx_queue_len) {
		qdisc = qdisc_create_dflt(dev, dev_queue,
					  &pfifo_fast_ops, TC_H_ROOT);
		if (!qdisc) {
			printk(KERN_INFO "%s: activation failed\n", dev->name);
			return;
		}

		/* Can by-pass the queue discipline for default qdisc */
		qdisc->flags |= TCQ_F_CAN_BYPASS;
	} else {
		qdisc =  &noqueue_qdisc;
	}
	dev_queue->qdisc_sleeping = qdisc;
}

创建noqueue

开始尝试直接删除设备默认的pfifo_fast队列，发现会出错：

# tc qdisc del dev vethd4ea root
RTNETLINK answers: No such file or directory
# tc  -s qdisc ls dev vethd4ea
qdisc pfifo_fast 0: root refcnt 2 bands 3 priomap  1 2 2 2 1 2 0 0 1 1 1 1 1 1 1 1
 Sent 29705382 bytes 441562 pkt (dropped 0, overlimits 0 requeues 0) 
 backlog 0b 0p requeues 0

后来看到Jesper Brouer给出一个替换默认队列的方式，尝试了一下，成功完成。

替换默认的qdisc队列

# tc qdisc replace dev vethd4ea root pfifo limit 100
# tc  -s qdisc ls dev vethd4ea                      
qdisc pfifo 8001: root refcnt 2 limit 100p
 Sent 264 bytes 4 pkt (dropped 0, overlimits 0 requeues 0) 
 backlog 0b 0p requeues 0 
# ip link show vethd4ea
9: vethd4ea: <BROADCAST,UP,LOWER_UP> mtu 1500 qdisc pfifo master docker0 state UP mode DEFAULT qlen 1000
link/ether 3a:15:3b:e1:d7:6d brd ff:ff:ff:ff:ff:ff

修改队列长度

# ifconfig vethd4ea txqueuelen 0

删除qdisc

# tc qdisc del dev vethd4ea root                    
# ip link show vethd4ea                
9: vethd4ea: <BROADCAST,UP,LOWER_UP> mtu 1500 qdisc noqueue master docker0 state UP mode DEFAULT 
link/ether 3a:15:3b:e1:d7:6d brd ff:ff:ff:ff:ff:ff

可以看到，UP的veth设备成功修改成noqueue。

Posted by kk

2020-05-22 11:24:00kernel, net

« qdisc 的创建过程 reuseport使用 »


report

Recommend

About Joyk


Aggregate valuable and interesting links.
Joyk means Joy of geeK