pkt_sched: sch_htb: Use workqueue to schedule after too many events.

Patrick McHardy <kaber@trash.net> suggested using a workqueue instead
of hrtimers to trigger netif_schedule() when there is a problem with
setting exact time of this event: 'The differnce - yeah, it shouldn't
make much, mainly wake up the qdisc earlier (but not too early) after
"too many events" occured _and_ no further enqueue events wake up the
qdisc anyways.'

Signed-off-by: Jarek Poplawski <jarkao2@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 21 insertions, 5 deletions

diff --git a/net/sched/sch_htb.c b/net/sched/sch_htb.c
index 826f92145261..355974f610c5 100644
--- a/net/sched/sch_htb.c
+++ b/net/sched/sch_htb.c
@@ -35,6 +35,7 @@
 #include <linux/list.h>
 #include <linux/compiler.h>
 #include <linux/rbtree.h>
+#include <linux/workqueue.h>
 #include <net/netlink.h>
 #include <net/pkt_sched.h>
 
@@ -156,6 +157,7 @@ struct htb_sched {
 
 #define HTB_WARN_TOOMANYEVENTS  0x1
         unsigned int warned;    /* only one warning */
+        struct work_struct work;
 };
 
 /* find class in global hash table using given handle */
@@ -659,7 +661,7 @@ static void htb_charge_class(struct htb_sched *q, struct htb_class *cl,
  * htb_do_events - make mode changes to classes at the level
  *
  * Scans event queue for pending events and applies them. Returns time of
- * next pending event (0 for no event in pq).
+ * next pending event (0 for no event in pq, q->now for too many events).
  * Note: Applied are events whose have cl->pq_key <= q->now.
  */
 static psched_time_t htb_do_events(struct htb_sched *q, int level,
@@ -687,12 +689,14 @@ static psched_time_t htb_do_events(struct htb_sched *q, int level,
                 if (cl->cmode != HTB_CAN_SEND)
                         htb_add_to_wait_tree(q, cl, diff);
         }
-        /* too much load - let's continue on next jiffie (including above) */
+
+        /* too much load - let's continue after a break for scheduling */
         if (!(q->warned & HTB_WARN_TOOMANYEVENTS)) {
                 printk(KERN_WARNING "htb: too many events!\n");
                 q->warned |= HTB_WARN_TOOMANYEVENTS;
         }
-        return q->now + 2 * PSCHED_TICKS_PER_SEC / HZ;
+
+        return q->now;
 }
 
 /* Returns class->node+prio from id-tree where classe's id is >= id. NULL
@@ -892,7 +896,10 @@ static struct sk_buff *htb_dequeue(struct Qdisc *sch)
                 }
         }
         sch->qstats.overlimits++;
-        qdisc_watchdog_schedule(&q->watchdog, next_event);
+        if (likely(next_event > q->now))
+                qdisc_watchdog_schedule(&q->watchdog, next_event);
+        else
+                schedule_work(&q->work);
 fin:
         return skb;
 }
@@ -962,6 +969,14 @@ static const struct nla_policy htb_policy[TCA_HTB_MAX + 1] = {
         [TCA_HTB_RTAB]  = { .type = NLA_BINARY, .len = TC_RTAB_SIZE },
 };
 
+static void htb_work_func(struct work_struct *work)
+{
+        struct htb_sched *q = container_of(work, struct htb_sched, work);
+        struct Qdisc *sch = q->watchdog.qdisc;
+
+        __netif_schedule(qdisc_root(sch));
+}
+
 static int htb_init(struct Qdisc *sch, struct nlattr *opt)
 {
         struct htb_sched *q = qdisc_priv(sch);
@@ -996,6 +1011,7 @@ static int htb_init(struct Qdisc *sch, struct nlattr *opt)
                 INIT_LIST_HEAD(q->drops + i);
 
         qdisc_watchdog_init(&q->watchdog, sch);
+        INIT_WORK(&q->work, htb_work_func);
         skb_queue_head_init(&q->direct_queue);
 
         q->direct_qlen = qdisc_dev(sch)->tx_queue_len;
@@ -1188,7 +1204,6 @@ static void htb_destroy_class(struct Qdisc *sch, struct htb_class *cl)
         kfree(cl);
 }
 
-/* always caled under BH & queue lock */
 static void htb_destroy(struct Qdisc *sch)
 {
         struct htb_sched *q = qdisc_priv(sch);
@@ -1196,6 +1211,7 @@ static void htb_destroy(struct Qdisc *sch)
         struct htb_class *cl;
         unsigned int i;
 
+        cancel_work_sync(&q->work);
         qdisc_watchdog_cancel(&q->watchdog);
         /* This line used to be after htb_destroy_class call below
            and surprisingly it worked in 2.4. But it must precede it