[hurd] 15/26: commit 9d21493b4beb8f918ba248032fefa393074a5e2b

[Samuel Thibault]

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sthibault pushed a commit to branch dde
in repository hurd.

commit befb192dd8647442a46603d919ae4b6a9ebff74c
Author: Eric Dumazet <address@hidden>
Date:   Sun May 17 20:55:16 2009 -0700

    commit 9d21493b4beb8f918ba248032fefa393074a5e2b
    
        net: tx scalability works : trans_start
    
        struct net_device trans_start field is a hot spot on SMP and high 
performance
        devices, particularly multi queues ones, because every transmitter 
dirties
        it. Is main use is tx watchdog and bonding alive checks.
    
        But as most devices dont use NETIF_F_LLTX, we have to lock
        a netdev_queue before calling their ndo_start_xmit(). So it makes
        sense to move trans_start from net_device to netdev_queue. Its update
        will occur on a already present (and in exclusive state) cache line, for
        free.
    
        We can do this transition smoothly. An old driver continue to
        update dev->trans_start, while an updated one updates txq->trans_start.
    
        Further patches could also put tx_bytes/tx_packets counters in
        netdev_queue to avoid dirtying dev->stats (vlan device comes to mind)
    
        Signed-off-by: Eric Dumazet <address@hidden>
        Signed-off-by: David S. Miller <address@hidden>
---
 libdde_linux26/contrib/include/linux/netdevice.h | 11 +++++++
 libdde_linux26/lib/src/net/sched/sch_generic.c   | 40 ++++++++++++++++++------
 2 files changed, 42 insertions(+), 9 deletions(-)

diff --git a/libdde_linux26/contrib/include/linux/netdevice.h 
b/libdde_linux26/contrib/include/linux/netdevice.h
index bb4fca1..4414989 100644
--- a/libdde_linux26/contrib/include/linux/netdevice.h
+++ b/libdde_linux26/contrib/include/linux/netdevice.h
@@ -462,6 +462,10 @@ struct netdev_queue {
        spinlock_t              _xmit_lock;
        int                     xmit_lock_owner;
        struct Qdisc            *qdisc_sleeping;
+       /*
+        * please use this field instead of dev->trans_start
+        */
+       unsigned long           trans_start;
 } ____cacheline_aligned_in_smp;
 
 
@@ -801,6 +805,11 @@ struct net_device
  * One part is mostly used on xmit path (device)
  */
        /* These may be needed for future network-power-down code. */
+
+       /*
+        * trans_start here is expensive for high speed devices on SMP,
+        * please use netdev_queue->trans_start instead.
+        */
        unsigned long           trans_start;    /* Time (in jiffies) of last Tx 
*/
 
        int                     watchdog_timeo; /* used by dev_watchdog() */
@@ -1477,6 +1486,8 @@ static inline int netif_carrier_ok(const struct 
net_device *dev)
        return !test_bit(__LINK_STATE_NOCARRIER, &dev->state);
 }
 
+extern unsigned long dev_trans_start(struct net_device *dev);
+
 extern void __netdev_watchdog_up(struct net_device *dev);
 
 extern void netif_carrier_on(struct net_device *dev);
diff --git a/libdde_linux26/lib/src/net/sched/sch_generic.c 
b/libdde_linux26/lib/src/net/sched/sch_generic.c
index a2acd6c..252ac98 100644
--- a/libdde_linux26/lib/src/net/sched/sch_generic.c
+++ b/libdde_linux26/lib/src/net/sched/sch_generic.c
@@ -200,6 +200,21 @@ void __qdisc_run(struct Qdisc *q)
        clear_bit(__QDISC_STATE_RUNNING, &q->state);
 }
 
+unsigned long dev_trans_start(struct net_device *dev)
+{
+       unsigned long val, res = dev->trans_start;
+       unsigned int i;
+
+       for (i = 0; i < dev->num_tx_queues; i++) {
+               val = netdev_get_tx_queue(dev, i)->trans_start;
+               if (val && time_after(val, res))
+                       res = val;
+       }
+       dev->trans_start = res;
+       return res;
+}
+EXPORT_SYMBOL(dev_trans_start);
+
 static void dev_watchdog(unsigned long arg)
 {
        struct net_device *dev = (struct net_device *)arg;
@@ -209,25 +224,30 @@ static void dev_watchdog(unsigned long arg)
                if (netif_device_present(dev) &&
                    netif_running(dev) &&
                    netif_carrier_ok(dev)) {
-                       int some_queue_stopped = 0;
+                       int some_queue_timedout = 0;
                        unsigned int i;
+                       unsigned long trans_start;
 
                        for (i = 0; i < dev->num_tx_queues; i++) {
                                struct netdev_queue *txq;
 
                                txq = netdev_get_tx_queue(dev, i);
-                               if (netif_tx_queue_stopped(txq)) {
-                                       some_queue_stopped = 1;
+                               /*
+                                * old device drivers set dev->trans_start
+                                */
+                               trans_start = txq->trans_start ? : 
dev->trans_start;
+                               if (netif_tx_queue_stopped(txq) &&
+                                   time_after(jiffies, (trans_start +
+                                                        dev->watchdog_timeo))) 
{
+                                       some_queue_timedout = 1;
                                        break;
                                }
                        }
 
-                       if (some_queue_stopped &&
-                           time_after(jiffies, (dev->trans_start +
-                                                dev->watchdog_timeo))) {
+                       if (some_queue_timedout) {
                                char drivername[64];
-                               WARN_ONCE(1, KERN_INFO "NETDEV WATCHDOG: %s 
(%s): transmit timed out\n",
-                                      dev->name, netdev_drivername(dev, 
drivername, 64));
+                               WARN_ONCE(1, KERN_INFO "NETDEV WATCHDOG: %s 
(%s): transmit queue %u timed out\n",
+                                      dev->name, netdev_drivername(dev, 
drivername, 64), i);
                                dev->netdev_ops->ndo_tx_timeout(dev);
                        }
                        if (!mod_timer(&dev->watchdog_timer,
@@ -612,8 +632,10 @@ static void transition_one_qdisc(struct net_device *dev,
                clear_bit(__QDISC_STATE_DEACTIVATED, &new_qdisc->state);
 
        rcu_assign_pointer(dev_queue->qdisc, new_qdisc);
-       if (need_watchdog_p && new_qdisc != &noqueue_qdisc)
+       if (need_watchdog_p && new_qdisc != &noqueue_qdisc) {
+               dev_queue->trans_start = 0;
                *need_watchdog_p = 1;
+       }
 }
 
 void dev_activate(struct net_device *dev)

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