netdev - [PATCH] net: factorize rt_do_flush for batch device unregistering

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Message-Id: <200911162308.59730.opurdila@ixiacom.com>
Date:	Mon, 16 Nov 2009 23:08:59 +0200
From:	Octavian Purdila <opurdila@...acom.com>
To:	netdev@...r.kernel.org
Cc:	Eric Dumazet <eric.dumazet@...il.com>
Subject: [PATCH] net: factorize rt_do_flush for batch device unregistering

Tests performed with per device sysctl/sysfs entries disabled:

$ insmod /lib/modules/dummy.ko numdummies=8000
$ time rmmod dummy

Without the patch:    With the patch:
real    0m 3.65s      real    0m 0.27s
user    0m 0.00s      user    0m 0.00s
sys     0m 3.42s      sys     0m 0.24s

Signed-off-by: Octavian Purdila <opurdila@...acom.com>
---
 net/core/dev.c          |   28 ++++++++++++++++++++++++++--
 net/ipv4/fib_frontend.c |   13 ++++++++-----
 2 files changed, 34 insertions(+), 7 deletions(-)

diff --git a/net/core/dev.c b/net/core/dev.c
index 4b24d79..b0a14f0 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -4720,7 +4720,8 @@ static void net_set_todo(struct net_device *dev)
 
 static void rollback_registered_many(struct list_head *head)
 {
-	struct net_device *dev;
+	struct net_device *dev, *aux, *fdev;
+	LIST_HEAD(rt_flush_list);
 
 	BUG_ON(dev_boot_phase);
 	ASSERT_RTNL();
@@ -4778,8 +4779,28 @@ static void rollback_registered_many(struct list_head *head)
 
 	synchronize_net();
 
-	list_for_each_entry(dev, head, unreg_list)
+	/* flush route cache by resending one NETDEV_UNREGISTER per namespace */
+	list_for_each_entry_safe(dev, aux, head, unreg_list) {
+		int needs_flush = 1;
+		list_for_each_entry(fdev, &rt_flush_list, unreg_list) {
+			if (dev_net(dev) == dev_net(fdev)) {
+				needs_flush = 0;
+				dev_put(dev);
+				break;
+			}
+		}
+		if (needs_flush) {
+			list_del(&dev->unreg_list);
+			list_add(&dev->unreg_list, &rt_flush_list);
+		}
+	}
+
+	list_for_each_entry_safe(dev, aux, &rt_flush_list, unreg_list) {
+		list_del_init(&dev->unreg_list);
+		call_netdevice_notifiers(NETDEV_UNREGISTER, dev);
+		list_add(&dev->unreg_list, head);
 		dev_put(dev);
+	}
 }
 
 static void rollback_registered(struct net_device *dev)
@@ -5374,6 +5395,9 @@ EXPORT_SYMBOL(unregister_netdevice_queue);
  *	unregister_netdevice_many - unregister many devices
  *	@head: list of devices
  *
+ *	WARNING: This function modifies the list. It may change the order of the
+ *	elements in the list. However, you can assume it does not add or delete
+ *	elements to/from the list.
  */
 void unregister_netdevice_many(struct list_head *head)
 {
diff --git a/net/ipv4/fib_frontend.c b/net/ipv4/fib_frontend.c
index 816e218..1972760 100644
--- a/net/ipv4/fib_frontend.c
+++ b/net/ipv4/fib_frontend.c
@@ -895,11 +895,11 @@ static void nl_fib_lookup_exit(struct net *net)
 	net->ipv4.fibnl = NULL;
 }
 
-static void fib_disable_ip(struct net_device *dev, int force)
+static void fib_disable_ip(struct net_device *dev, int force, int delay)
 {
 	if (fib_sync_down_dev(dev, force))
 		fib_flush(dev_net(dev));
-	rt_cache_flush(dev_net(dev), 0);
+	rt_cache_flush(dev_net(dev), delay);
 	arp_ifdown(dev);
 }
 
@@ -922,7 +922,7 @@ static int fib_inetaddr_event(struct notifier_block *this, unsigned long event,
 			/* Last address was deleted from this interface.
 			   Disable IP.
 			 */
-			fib_disable_ip(dev, 1);
+			fib_disable_ip(dev, 1, 0);
 		} else {
 			rt_cache_flush(dev_net(dev), -1);
 		}
@@ -937,7 +937,10 @@ static int fib_netdev_event(struct notifier_block *this, unsigned long event, vo
 	struct in_device *in_dev = __in_dev_get_rtnl(dev);
 
 	if (event == NETDEV_UNREGISTER) {
-		fib_disable_ip(dev, 2);
+		/* if this event is part of a batch then don't flush the cache
+		 * now; we will receive another event at the end of the batch */
+		int rt_flush = list_empty(&dev->unreg_list) ? 0 : -1;
+		fib_disable_ip(dev, 2, rt_flush);
 		return NOTIFY_DONE;
 	}
 
@@ -955,7 +958,7 @@ static int fib_netdev_event(struct notifier_block *this, unsigned long event, vo
 		rt_cache_flush(dev_net(dev), -1);
 		break;
 	case NETDEV_DOWN:
-		fib_disable_ip(dev, 0);
+		fib_disable_ip(dev, 0, 0);
 		break;
 	case NETDEV_CHANGEMTU:
 	case NETDEV_CHANGE:
-- 
1.5.6.5

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