linkwatch: linkwatch_forget_dev() to speedup device dismantle
Herbert Xu a écrit :
> On Tue, Nov 17, 2009 at 04:26:04AM -0800, David Miller wrote:
>> Really, the link watch stuff is just due for a redesign. I don't
>> think a simple hack is going to cut it this time, sorry Eric :-)
>
> I have no objections against any redesigns, but since the only
> caller of linkwatch_forget_dev runs in process context with the
> RTNL, it could also legally emit those events.
Thanks guys, here an updated version then, before linkwatch surgery ?
In this version, I force the event to be sent synchronously.
[PATCH net-next-2.6] linkwatch: linkwatch_forget_dev() to speedup device dismantle
time ip link del eth3.103 ; time ip link del eth3.104 ; time ip link del eth3.105
real 0m0.266s
user 0m0.000s
sys 0m0.001s
real 0m0.770s
user 0m0.000s
sys 0m0.000s
real 0m1.022s
user 0m0.000s
sys 0m0.000s
One problem of current schem in vlan dismantle phase is the
holding of device done by following chain :
vlan_dev_stop() ->
netif_carrier_off(dev) ->
linkwatch_fire_event(dev) ->
dev_hold() ...
And __linkwatch_run_queue() runs up to one second later...
A generic fix to this problem is to add a linkwatch_forget_dev() method
to unlink the device from the list of watched devices.
dev->link_watch_next becomes dev->link_watch_list (and use a bit more memory),
to be able to unlink device in O(1).
After patch :
time ip link del eth3.103 ; time ip link del eth3.104 ; time ip link del eth3.105
real 0m0.024s
user 0m0.000s
sys 0m0.000s
real 0m0.032s
user 0m0.000s
sys 0m0.001s
real 0m0.033s
user 0m0.000s
sys 0m0.000s
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index c8fa462..97873e3 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -896,7 +896,7 @@
/* device index hash chain */
struct hlist_node index_hlist;
- struct net_device *link_watch_next;
+ struct list_head link_watch_list;
/* register/unregister state machine */
enum { NETREG_UNINITIALIZED=0,
@@ -1600,6 +1600,7 @@
*/
extern void linkwatch_fire_event(struct net_device *dev);
+extern void linkwatch_forget_dev(struct net_device *dev);
/**
* netif_carrier_ok - test if carrier present
diff --git a/net/core/dev.c b/net/core/dev.c
index e25fe5d..c128af7 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -5085,6 +5085,8 @@
{
unsigned long rebroadcast_time, warning_time;
+ linkwatch_forget_dev(dev);
+
rebroadcast_time = warning_time = jiffies;
while (atomic_read(&dev->refcnt) != 0) {
if (time_after(jiffies, rebroadcast_time + 1 * HZ)) {
@@ -5311,6 +5313,7 @@
INIT_LIST_HEAD(&dev->napi_list);
INIT_LIST_HEAD(&dev->unreg_list);
+ INIT_LIST_HEAD(&dev->link_watch_list);
dev->priv_flags = IFF_XMIT_DST_RELEASE;
setup(dev);
strcpy(dev->name, name);
diff --git a/net/core/link_watch.c b/net/core/link_watch.c
index bf8f7af..5910b55 100644
--- a/net/core/link_watch.c
+++ b/net/core/link_watch.c
@@ -35,7 +35,7 @@
static void linkwatch_event(struct work_struct *dummy);
static DECLARE_DELAYED_WORK(linkwatch_work, linkwatch_event);
-static struct net_device *lweventlist;
+static LIST_HEAD(lweventlist);
static DEFINE_SPINLOCK(lweventlist_lock);
static unsigned char default_operstate(const struct net_device *dev)
@@ -89,8 +89,10 @@
unsigned long flags;
spin_lock_irqsave(&lweventlist_lock, flags);
- dev->link_watch_next = lweventlist;
- lweventlist = dev;
+ if (list_empty(&dev->link_watch_list)) {
+ list_add_tail(&dev->link_watch_list, &lweventlist);
+ dev_hold(dev);
+ }
spin_unlock_irqrestore(&lweventlist_lock, flags);
}
@@ -133,9 +135,35 @@
}
+static void linkwatch_do_dev(struct net_device *dev)
+{
+ /*
+ * Make sure the above read is complete since it can be
+ * rewritten as soon as we clear the bit below.
+ */
+ smp_mb__before_clear_bit();
+
+ /* We are about to handle this device,
+ * so new events can be accepted
+ */
+ clear_bit(__LINK_STATE_LINKWATCH_PENDING, &dev->state);
+
+ rfc2863_policy(dev);
+ if (dev->flags & IFF_UP) {
+ if (netif_carrier_ok(dev))
+ dev_activate(dev);
+ else
+ dev_deactivate(dev);
+
+ netdev_state_change(dev);
+ }
+ dev_put(dev);
+}
+
static void __linkwatch_run_queue(int urgent_only)
{
- struct net_device *next;
+ struct net_device *dev;
+ LIST_HEAD(wrk);
/*
* Limit the number of linkwatch events to one
@@ -153,46 +181,40 @@
clear_bit(LW_URGENT, &linkwatch_flags);
spin_lock_irq(&lweventlist_lock);
- next = lweventlist;
- lweventlist = NULL;
- spin_unlock_irq(&lweventlist_lock);
+ list_splice_init(&lweventlist, &wrk);
- while (next) {
- struct net_device *dev = next;
+ while (!list_empty(&wrk)) {
- next = dev->link_watch_next;
+ dev = list_first_entry(&wrk, struct net_device, link_watch_list);
+ list_del_init(&dev->link_watch_list);
if (urgent_only && !linkwatch_urgent_event(dev)) {
- linkwatch_add_event(dev);
+ list_add_tail(&dev->link_watch_list, &lweventlist);
continue;
}
-
- /*
- * Make sure the above read is complete since it can be
- * rewritten as soon as we clear the bit below.
- */
- smp_mb__before_clear_bit();
-
- /* We are about to handle this device,
- * so new events can be accepted
- */
- clear_bit(__LINK_STATE_LINKWATCH_PENDING, &dev->state);
-
- rfc2863_policy(dev);
- if (dev->flags & IFF_UP) {
- if (netif_carrier_ok(dev))
- dev_activate(dev);
- else
- dev_deactivate(dev);
-
- netdev_state_change(dev);
- }
-
- dev_put(dev);
+ spin_unlock_irq(&lweventlist_lock);
+ linkwatch_do_dev(dev);
+ spin_lock_irq(&lweventlist_lock);
}
- if (lweventlist)
+ if (!list_empty(&lweventlist))
linkwatch_schedule_work(0);
+ spin_unlock_irq(&lweventlist_lock);
+}
+
+void linkwatch_forget_dev(struct net_device *dev)
+{
+ unsigned long flags;
+ int clean = 0;
+
+ spin_lock_irqsave(&lweventlist_lock, flags);
+ if (!list_empty(&dev->link_watch_list)) {
+ list_del_init(&dev->link_watch_list);
+ clean = 1;
+ }
+ spin_unlock_irqrestore(&lweventlist_lock, flags);
+ if (clean)
+ linkwatch_do_dev(dev);
}
@@ -216,8 +238,6 @@
bool urgent = linkwatch_urgent_event(dev);
if (!test_and_set_bit(__LINK_STATE_LINKWATCH_PENDING, &dev->state)) {
- dev_hold(dev);
-
linkwatch_add_event(dev);
} else if (!urgent)
return;