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Commit 44345724 authored by Octavian Purdila's avatar Octavian Purdila Committed by David S. Miller
Browse files

net: factorize sync-rcu call in unregister_netdevice_many 



Add dev_close_many and dev_deactivate_many to factorize another
sync-rcu operation on the netdevice unregister path.

$ modprobe dummy numdummies=10000
$ ip link set dev dummy* up
$ time rmmod dummy

Without the patch           With the patch

real    0m 24.63s           real    0m 5.15s
user    0m 0.00s            user    0m 0.00s
sys     0m 6.05s            sys     0m 5.14s

Signed-off-by: default avatarOctavian Purdila <opurdila@ixiacom.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent c6c8fea2

include/net/sch_generic.h

+1 −0
Original line number Diff line number Diff line
@@ -321,6 +321,7 @@ extern void dev_init_scheduler(struct net_device *dev); 
extern void dev_shutdown(struct net_device *dev);

extern void dev_activate(struct net_device *dev);

extern void dev_deactivate(struct net_device *dev);

extern void dev_deactivate_many(struct list_head *head);

extern struct Qdisc *dev_graft_qdisc(struct netdev_queue *dev_queue,

				     struct Qdisc *qdisc);

extern void qdisc_reset(struct Qdisc *qdisc);

net/core/dev.c

+76 −42
Original line number Diff line number Diff line
@@ -1222,13 +1222,14 @@ int dev_open(struct net_device *dev) 
}

EXPORT_SYMBOL(dev_open);



static int __dev_close(struct net_device *dev)

static int __dev_close_many(struct list_head *head)

{

	const struct net_device_ops *ops = dev->netdev_ops;

	struct net_device *dev;



	ASSERT_RTNL();

	might_sleep();



	list_for_each_entry(dev, head, unreg_list) {

		/*

		 *	Tell people we are going down, so that they can

		 *	prepare to death, when device is still operating.
@@ -1237,15 +1238,19 @@ static int __dev_close(struct net_device *dev) 


		clear_bit(__LINK_STATE_START, &dev->state);



	/* Synchronize to scheduled poll. We cannot touch poll list,

	 * it can be even on different cpu. So just clear netif_running().

		/* Synchronize to scheduled poll. We cannot touch poll list, it

		 * can be even on different cpu. So just clear netif_running().

		 *

		 * dev->stop() will invoke napi_disable() on all of it's

		 * napi_struct instances on this device.

		 */

		smp_mb__after_clear_bit(); /* Commit netif_running(). */

	}



	dev_deactivate_many(head);



	dev_deactivate(dev);

	list_for_each_entry(dev, head, unreg_list) {

		const struct net_device_ops *ops = dev->netdev_ops;



		/*

		 *	Call the device specific close. This cannot fail.
@@ -1267,7 +1272,40 @@ static int __dev_close(struct net_device *dev) 
		 *	Shutdown NET_DMA

		 */

		net_dmaengine_put();

	}



	return 0;

}



static int __dev_close(struct net_device *dev)

{

	LIST_HEAD(single);



	list_add(&dev->unreg_list, &single);

	return __dev_close_many(&single);

}



int dev_close_many(struct list_head *head)

{

	struct net_device *dev, *tmp;

	LIST_HEAD(tmp_list);



	list_for_each_entry_safe(dev, tmp, head, unreg_list)

		if (!(dev->flags & IFF_UP))

			list_move(&dev->unreg_list, &tmp_list);



	__dev_close_many(head);



	/*

	 * Tell people we are down

	 */

	list_for_each_entry(dev, head, unreg_list) {

		rtmsg_ifinfo(RTM_NEWLINK, dev, IFF_UP|IFF_RUNNING);

		call_netdevice_notifiers(NETDEV_DOWN, dev);

	}



	/* rollback_registered_many needs the complete original list */

	list_splice(&tmp_list, head);

	return 0;

}
@@ -1282,16 +1320,10 @@ static int __dev_close(struct net_device *dev) 
 */

int dev_close(struct net_device *dev)

{

	if (!(dev->flags & IFF_UP))

		return 0;



	__dev_close(dev);

	LIST_HEAD(single);



	/*

	 * Tell people we are down

	 */

	rtmsg_ifinfo(RTM_NEWLINK, dev, IFF_UP|IFF_RUNNING);

	call_netdevice_notifiers(NETDEV_DOWN, dev);

	list_add(&dev->unreg_list, &single);

	dev_close_many(&single);



	return 0;

}
@@ -4963,10 +4995,12 @@ static void rollback_registered_many(struct list_head *head) 
		}



		BUG_ON(dev->reg_state != NETREG_REGISTERED);

	}



	/* If device is running, close it first. */

		dev_close(dev);

	dev_close_many(head);



	list_for_each_entry(dev, head, unreg_list) {

		/* And unlink it from device chain. */

		unlist_netdevice(dev);

net/sched/sch_generic.c

+22 −7
Original line number Diff line number Diff line
@@ -810,22 +810,37 @@ static bool some_qdisc_is_busy(struct net_device *dev) 
	return false;

}



void dev_deactivate(struct net_device *dev)

void dev_deactivate_many(struct list_head *head)

{

	netdev_for_each_tx_queue(dev, dev_deactivate_queue, &noop_qdisc);

	struct net_device *dev;



	list_for_each_entry(dev, head, unreg_list) {

		netdev_for_each_tx_queue(dev, dev_deactivate_queue,

					 &noop_qdisc);

		if (dev_ingress_queue(dev))

		dev_deactivate_queue(dev, dev_ingress_queue(dev), &noop_qdisc);

			dev_deactivate_queue(dev, dev_ingress_queue(dev),

					     &noop_qdisc);



		dev_watchdog_down(dev);

	}



	/* Wait for outstanding qdisc-less dev_queue_xmit calls. */

	synchronize_rcu();



	/* Wait for outstanding qdisc_run calls. */

	list_for_each_entry(dev, head, unreg_list)

		while (some_qdisc_is_busy(dev))

			yield();

}



void dev_deactivate(struct net_device *dev)

{

	LIST_HEAD(single);



	list_add(&dev->unreg_list, &single);

	dev_deactivate_many(&single);

}



static void dev_init_scheduler_queue(struct net_device *dev,

				     struct netdev_queue *dev_queue,

				     void *_qdisc)