net: reimplement softnet_data.output_queue as a FIFO queue

reimplement softnet_data.output_queue as a FIFO queue to keep the
fairness among the qdiscs rescheduled.

Signed-off-by: Changli Gao <xiaosuo@gmail.com>
Acked-by: Eric Dumazet <eric.dumazet@gmail.com>
----
 include/linux/netdevice.h |    1 +
 net/core/dev.c            |   22 ++++++++++++----------
 2 files changed, 13 insertions(+), 10 deletions(-)
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 3c5ed5f..c04ca24 100644 (file)
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -1385,6 +1385,7 @@ static inline int unregister_gifconf(unsigned int family)
  */
 struct softnet_data {
        struct Qdisc            *output_queue;
+       struct Qdisc            **output_queue_tailp;
        struct list_head        poll_list;
        struct sk_buff          *completion_queue;
 

diff --git a/net/core/dev.c b/net/core/dev.c
index 4d43f1a..3d31491 100644 (file)
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -1557,8 +1557,9 @@ static inline void __netif_reschedule(struct Qdisc *q)
 
        local_irq_save(flags);
        sd = &__get_cpu_var(softnet_data);
-       q->next_sched = sd->output_queue;
-       sd->output_queue = q;
+       q->next_sched = NULL;
+       *sd->output_queue_tailp = q;
+       sd->output_queue_tailp = &q->next_sched;
        raise_softirq_irqoff(NET_TX_SOFTIRQ);
        local_irq_restore(flags);
 }
@@ -2529,6 +2530,7 @@ static void net_tx_action(struct softirq_action *h)
                local_irq_disable();
                head = sd->output_queue;
                sd->output_queue = NULL;
+               sd->output_queue_tailp = &sd->output_queue;
                local_irq_enable();
 
                while (head) {
@@ -5594,7 +5596,6 @@ static int dev_cpu_callback(struct notifier_block *nfb,
                            void *ocpu)
 {
        struct sk_buff **list_skb;
-       struct Qdisc **list_net;
        struct sk_buff *skb;
        unsigned int cpu, oldcpu = (unsigned long)ocpu;
        struct softnet_data *sd, *oldsd;
@@ -5615,13 +5616,13 @@ static int dev_cpu_callback(struct notifier_block *nfb,
        *list_skb = oldsd->completion_queue;
        oldsd->completion_queue = NULL;
 
-       /* Find end of our output_queue. */
-       list_net = &sd->output_queue;
-       while (*list_net)
-               list_net = &(*list_net)->next_sched;
        /* Append output queue from offline CPU. */
-       *list_net = oldsd->output_queue;
-       oldsd->output_queue = NULL;
+       if (oldsd->output_queue) {
+               *sd->output_queue_tailp = oldsd->output_queue;
+               sd->output_queue_tailp = oldsd->output_queue_tailp;
+               oldsd->output_queue = NULL;
+               oldsd->output_queue_tailp = &oldsd->output_queue;
+       }
 
        raise_softirq_irqoff(NET_TX_SOFTIRQ);
        local_irq_enable();
@@ -5851,7 +5852,8 @@ static int __init net_dev_init(void)
                skb_queue_head_init(&sd->input_pkt_queue);
                sd->completion_queue = NULL;
                INIT_LIST_HEAD(&sd->poll_list);
-
+               sd->output_queue = NULL;
+               sd->output_queue_tailp = &sd->output_queue;
 #ifdef CONFIG_RPS
                sd->csd.func = rps_trigger_softirq;
                sd->csd.info = sd;