From e014debecd3ee3832e6476b3a9c948edfcfd1250 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Tue, 17 Nov 2009 05:59:21 +0000 Subject: [PATCH] linkwatch: linkwatch_forget_dev() to speedup device dismantle MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 Signed-off-by: David S. Miller --- include/linux/netdevice.h | 3 +- net/core/dev.c | 3 ++ net/core/link_watch.c | 94 ++++++++++++++++++++++++--------------- 3 files changed, 62 insertions(+), 38 deletions(-) diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h index c8fa4627de0..97873e31661 100644 --- a/include/linux/netdevice.h +++ b/include/linux/netdevice.h @@ -896,7 +896,7 @@ struct net_device { /* 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 @@ static inline void dev_hold(struct net_device *dev) */ 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 e25fe5d9343..c128af708eb 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -5085,6 +5085,8 @@ static void netdev_wait_allrefs(struct net_device *dev) { 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 @@ struct net_device *alloc_netdev_mq(int sizeof_priv, const char *name, 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 bf8f7af699d..5910b555a54 100644 --- a/net/core/link_watch.c +++ b/net/core/link_watch.c @@ -35,7 +35,7 @@ static unsigned long linkwatch_nextevent; 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 @@ static void linkwatch_add_event(struct net_device *dev) 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_schedule_work(int urgent) } +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 @@ static void __linkwatch_run_queue(int urgent_only) 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 @@ void linkwatch_fire_event(struct net_device *dev) 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;