The current call to __qdisc_dequeue_head leads to a branch
misprediction for every loop iteration, the fact that the
most common priority is 2 makes this even worse. This issue
has been brought up by Eric Dumazet <[EMAIL PROTECTED]>
but unlike his solution which was to manually unroll the loop,
this approach preserves the possibility to increase the number
of bands at compile time.
Signed-off-by: Thomas Graf <[EMAIL PROTECTED]>
Index: net-2.6/net/sched/sch_generic.c
===================================================================
--- net-2.6.orig/net/sched/sch_generic.c 2005-07-06 15:26:47.000000000
+0200
+++ net-2.6/net/sched/sch_generic.c 2005-07-17 20:27:56.000000000 +0200
@@ -331,11 +331,10 @@
int prio;
struct sk_buff_head *list = qdisc_priv(qdisc);
- for (prio = 0; prio < PFIFO_FAST_BANDS; prio++, list++) {
- struct sk_buff *skb = __qdisc_dequeue_head(qdisc, list);
- if (skb) {
+ for (prio = 0; prio < PFIFO_FAST_BANDS; prio++) {
+ if (!skb_queue_empty(list + prio)) {
qdisc->q.qlen--;
- return skb;
+ return __qdisc_dequeue_head(qdisc, list + prio);
}
}
-
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