On Fri, 2016-06-10 at 16:41 -0700, Eric Dumazet wrote:
> Looks like it is only there as some optimization attempt.
>
> Since __QDISC_STATE_THROTTLED set/unset is way too expensive,
> and netem is the last user, just remove this check.
>
> Signed-off-by: Eric Dumazet <eduma...@google.com>
> ---
> net/sched/sch_netem.c | 3 ---
> 1 file changed, 3 deletions(-)
>
> diff --git a/net/sched/sch_netem.c b/net/sched/sch_netem.c
> index 9ca7947ab643..2dbe732ca135 100644
> --- a/net/sched/sch_netem.c
> +++ b/net/sched/sch_netem.c
> @@ -582,9 +582,6 @@ static struct sk_buff *netem_dequeue(struct Qdisc *sch)
> struct sk_buff *skb;
> struct rb_node *p;
>
> - if (qdisc_is_throttled(sch))
> - return NULL;
> -
> tfifo_dequeue:
> skb = __skb_dequeue(&sch->q);
> if (skb) {
Note that this commit (42117927cab5a13192ecc227bea19da5059ffc6c
"net_sched: netem: remove qdisc_is_throttled() use")
is a stable candidate, as it incidentally removes one long standing bug.
Namely, we were not calling qdisc_unthrottled() from netem enqueue(), so
we would be forced to wait a timer activation to be able to drain the
queue(s).
This matters with either a jitter, or a "tc qdisc change ... delay <new
delay>"
