tree 56f02114d9e65d60c0f3a0658602e7e193f226bd
parent d7c7ed4dbc66c5f4dfa5615cdfc5009af3b3b137
author Thomas Graf <[EMAIL PROTECTED]> Tue, 19 Jul 2005 03:30:53 -0700
committer David S. Miller <[EMAIL PROTECTED]> Tue, 19 Jul 2005 03:30:53 -0700
[PKT_SCHED]: Reduce branch mispredictions in pfifo_fast_dequeue
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]>
Signed-off-by: David S. Miller <[EMAIL PROTECTED]>
net/sched/sch_generic.c | 7 +++----
1 files changed, 3 insertions(+), 4 deletions(-)
diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c
--- a/net/sched/sch_generic.c
+++ b/net/sched/sch_generic.c
@@ -331,11 +331,10 @@ static struct sk_buff *pfifo_fast_dequeu
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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