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authorThomas Graf <tgraf@suug.ch>2005-07-18 13:30:53 -0700
committerDavid S. Miller <davem@davemloft.net>2005-07-18 13:30:53 -0700
commit452f299da3253f65020143f743c2e207b752547b (patch)
tree56f02114d9e65d60c0f3a0658602e7e193f226bd /net
parentd7c7ed4dbc66c5f4dfa5615cdfc5009af3b3b137 (diff)
downloadtalos-op-linux-452f299da3253f65020143f743c2e207b752547b.tar.gz
talos-op-linux-452f299da3253f65020143f743c2e207b752547b.zip
[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 <dada1@cosmosbay.com> 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 <tgraf@suug.ch> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net')
-rw-r--r--net/sched/sch_generic.c7
1 files changed, 3 insertions, 4 deletions
diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c
index 73e218e646ac..8edefd5d095d 100644
--- a/net/sched/sch_generic.c
+++ b/net/sched/sch_generic.c
@@ -331,11 +331,10 @@ static struct sk_buff *pfifo_fast_dequeue(struct Qdisc* qdisc)
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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