Commit:     8236632fb3532188c75656421e29f5ab51b47db7
Parent:     854d8363f37491c955b0edc60d37b62f3d71bb67
Author:     Jamal Hadi Salim <[EMAIL PROTECTED]>
AuthorDate: Tue Sep 25 19:27:13 2007 -0700
Committer:  David S. Miller <[EMAIL PROTECTED]>
CommitDate: Wed Oct 10 16:52:15 2007 -0700

    [NET_SCHED]: explict hold dev tx lock
    For N cpus, with full throttle traffic on all N CPUs, funneling traffic
    to the same ethernet device, the devices queue lock is contended by all
    N CPUs constantly. The TX lock is only contended by a max of 2 CPUS.
    In the current mode of operation, after all the work of entering the
    dequeue region, we may endup aborting the path if we are unable to get
    the tx lock and go back to contend for the queue lock. As N goes up,
    this gets worse.
    The changes in this patch result in a small increase in performance
    with a 4CPU (2xdual-core) with no irq binding. Both e1000 and tg3
    showed similar behavior;
    Signed-off-by: Jamal Hadi Salim <[EMAIL PROTECTED]>
    Signed-off-by: David S. Miller <[EMAIL PROTECTED]>
 net/sched/sch_generic.c |   19 ++-----------------
 1 files changed, 2 insertions(+), 17 deletions(-)

diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c
index e970e8e..95ae119 100644
--- a/net/sched/sch_generic.c
+++ b/net/sched/sch_generic.c
@@ -134,34 +134,19 @@ static inline int qdisc_restart(struct net_device *dev)
        struct Qdisc *q = dev->qdisc;
        struct sk_buff *skb;
-       unsigned lockless;
        int ret;
        /* Dequeue packet */
        if (unlikely((skb = dev_dequeue_skb(dev, q)) == NULL))
                return 0;
-       /*
-        * When the driver has LLTX set, it does its own locking in
-        * start_xmit. These checks are worth it because even uncongested
-        * locks can be quite expensive. The driver can do a trylock, as
-        * is being done here; in case of lock contention it should return
-        * NETDEV_TX_LOCKED and the packet will be requeued.
-        */
-       lockless = (dev->features & NETIF_F_LLTX);
-       if (!lockless && !netif_tx_trylock(dev)) {
-               /* Another CPU grabbed the driver tx lock */
-               return handle_dev_cpu_collision(skb, dev, q);
-       }
        /* And release queue */
+       HARD_TX_LOCK(dev, smp_processor_id());
        ret = dev_hard_start_xmit(skb, dev);
-       if (!lockless)
-               netif_tx_unlock(dev);
+       HARD_TX_UNLOCK(dev);
        q = dev->qdisc;
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