net: sched: remove remaining uses for qdisc_qlen in xmit path

sch_direct_xmit() uses qdisc_qlen as a return value but all call sites
of the routine only check if it is zero or not. Simplify the logic so
that we don't need to return an actual queue length value.

This introduces a case now where sch_direct_xmit would have returned
a qlen of zero but now it returns true. However in this case all
call sites of sch_direct_xmit will implement a dequeue() and get
a null skb and abort. This trades tracking qlen in the hotpath for
an extra dequeue operation. Overall this seems to be good for
performance.

Signed-off-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/net/pkt_sched.h b/include/net/pkt_sched.h
index 4eea7198898ebef6e1b0b32d7588262e33ed1759..2404692288519514fcbf81621925b300b64cdba7 100644 (file)
--- a/include/net/pkt_sched.h
+++ b/include/net/pkt_sched.h
@@ -105,9 +105,9 @@ struct qdisc_rate_table *qdisc_get_rtab(struct tc_ratespec *r,
 void qdisc_put_rtab(struct qdisc_rate_table *tab);
 void qdisc_put_stab(struct qdisc_size_table *tab);
 void qdisc_warn_nonwc(const char *txt, struct Qdisc *qdisc);
-int sch_direct_xmit(struct sk_buff *skb, struct Qdisc *q,
-                   struct net_device *dev, struct netdev_queue *txq,
-                   spinlock_t *root_lock, bool validate);
+bool sch_direct_xmit(struct sk_buff *skb, struct Qdisc *q,
+                    struct net_device *dev, struct netdev_queue *txq,
+                    spinlock_t *root_lock, bool validate);
 
 void __qdisc_run(struct Qdisc *q);
 

diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c
index ec757f66896a55cd401986284c36c5de9f2078bc..cbc0a9a00e30ec6598d357847c41ee52fc96368d 100644 (file)
--- a/net/sched/sch_generic.c
+++ b/net/sched/sch_generic.c
@@ -164,12 +164,12 @@ trace:
  * only one CPU can execute this function.
  *
  * Returns to the caller:
- *                             0  - queue is empty or throttled.
- *                             >0 - queue is not empty.
+ *                             false  - hardware queue frozen backoff
+ *                             true   - feel free to send more pkts
  */
-int sch_direct_xmit(struct sk_buff *skb, struct Qdisc *q,
-                   struct net_device *dev, struct netdev_queue *txq,
-                   spinlock_t *root_lock, bool validate)
+bool sch_direct_xmit(struct sk_buff *skb, struct Qdisc *q,
+                    struct net_device *dev, struct netdev_queue *txq,
+                    spinlock_t *root_lock, bool validate)
 {
        int ret = NETDEV_TX_BUSY;
 
@@ -190,28 +190,26 @@ int sch_direct_xmit(struct sk_buff *skb, struct Qdisc *q,
        } else {
                if (root_lock)
                        spin_lock(root_lock);
-               return qdisc_qlen(q);
+               return true;
        }
 
        if (root_lock)
                spin_lock(root_lock);
 
-       if (dev_xmit_complete(ret)) {
-               /* Driver sent out skb successfully or skb was consumed */
-               ret = qdisc_qlen(q);
-       } else {
+       if (!dev_xmit_complete(ret)) {
                /* Driver returned NETDEV_TX_BUSY - requeue skb */
                if (unlikely(ret != NETDEV_TX_BUSY))
                        net_warn_ratelimited("BUG %s code %d qlen %d\n",
                                             dev->name, ret, q->q.qlen);
 
-               ret = dev_requeue_skb(skb, q);
+               dev_requeue_skb(skb, q);
+               return false;
        }
 
        if (ret && netif_xmit_frozen_or_stopped(txq))
-               ret = 0;
+               return false;
 
-       return ret;
+       return true;
 }
 
 /*
@@ -233,7 +231,7 @@ int sch_direct_xmit(struct sk_buff *skb, struct Qdisc *q,
  *                             >0 - queue is not empty.
  *
  */
-static inline int qdisc_restart(struct Qdisc *q, int *packets)
+static inline bool qdisc_restart(struct Qdisc *q, int *packets)
 {
        spinlock_t *root_lock = NULL;
        struct netdev_queue *txq;
@@ -244,7 +242,7 @@ static inline int qdisc_restart(struct Qdisc *q, int *packets)
        /* Dequeue packet */
        skb = dequeue_skb(q, &validate, packets);
        if (unlikely(!skb))
-               return 0;
+               return false;
 
        if (!(q->flags & TCQ_F_NOLOCK))
                root_lock = qdisc_lock(q);