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net: Fix high overhead of vlan sub-device teardown.

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When a networking device is taken down that has a non-trivial number
of VLAN devices configured under it, we eat a full synchronize_net()
for every such VLAN device.

This is because of the call chain:

	NETDEV_DOWN notifier
	--> vlan_device_event()
		--> dev_change_flags()
		--> __dev_change_flags()
		--> __dev_close()
		--> __dev_close_many()
		--> dev_deactivate_many()
			--> synchronize_net()

This is kind of rediculous because we already have infrastructure for
batching doing operation X to a list of net devices so that we only
incur one sync.

So make use of that by exporting dev_close_many() and adjusting it's
interfaace so that the caller can fully manage the batch list.  Use
this in vlan_device_event() and all the overhead goes away.

Reported-by: Salam Noureddine <noureddine@arista.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
David S. Miller
2015-03-18 22:52:33 -04:00
parent 738e6d30d3
commit 99c4a26a15
3 changed files with 21 additions and 8 deletions
Download Patch File Download Diff File Expand all files Collapse all files
net/8021q/vlan.c
+14 -4
View File
@@ -413,7 +413,10 @@ static int vlan_device_event(struct notifier_block *unused, unsigned long event,
vlan_transfer_features(dev, vlandev);
break;
case NETDEV_DOWN:
case NETDEV_DOWN: {
struct net_device *tmp;
LIST_HEAD(close_list);
if (dev->features & NETIF_F_HW_VLAN_CTAG_FILTER)
vlan_vid_del(dev, htons(ETH_P_8021Q), 0);
@@ -425,11 +428,18 @@ static int vlan_device_event(struct notifier_block *unused, unsigned long event,
vlan = vlan_dev_priv(vlandev);
if (!(vlan->flags & VLAN_FLAG_LOOSE_BINDING))
dev_change_flags(vlandev, flgs & ~IFF_UP);
netif_stacked_transfer_operstate(dev, vlandev);
list_add(&vlandev->close_list, &close_list);
}
break;
dev_close_many(&close_list, false);
list_for_each_entry_safe(vlandev, tmp, &close_list, close_list) {
netif_stacked_transfer_operstate(dev, vlandev);
list_del_init(&vlandev->close_list);
}
list_del(&close_list);
break;
}
case NETDEV_UP:
/* Put all VLANs for this dev in the up state too. */
vlan_group_for_each_dev(grp, i, vlandev) {