[Subject: Re: [PATCH 00/14]: Killing qdisc->ops->requeue().]
On Tue, Oct 14, 2008 at 10:44:13PM +0200, Patrick McHardy wrote:
...

I think we really need a peek operation since most qdiscs do have
some internal priorization. The question is whether all qdiscs need
it; I tend to think no. Plugging two non-work-conserving qdiscs
together doesn't make much sense, so we could just prevent this.
This means we would only need to add ->peek support to the
work-conserving qdiscs, which looks pretty easy in all cases.
We actually don't even have to prevent plugging two non-work-conserving
qdiscs, the ones that need the peek operation could just check whether
the inner qdisc supports it.

Just as a demonstration how easy adding a peek operation to the
work-conserving qdiscs actually is. It doesn't need to keep or change
any internal state in many cases thanks to the guarantee that the
packet will either be dequeued or, if another packet arrives, the
upper qdisc will immediately ->peek again to reevaluate the state.

So here is my try (I hope I didn't miss Patrick's intentions to much).

PATCH 6/6 adds my simple idea not to prevent even nonsense configs.
It is optional.

Thanks,
Jarek P.

PS: after this patchset only netem_enqueue() needs qdisc->requeue(),
but I hope this won't take too long.

 include/net/sch_generic.h |   29 +++++++++++++++++++++++++++++
 net/sched/sch_api.c       |    6 ++++++
 net/sched/sch_atm.c       |   23 ++++++++++++++++++-----
 net/sched/sch_blackhole.c |    1 +
 net/sched/sch_cbq.c       |    1 +
 net/sched/sch_dsmark.c    |   10 ++++++++++
 net/sched/sch_fifo.c      |    2 ++
 net/sched/sch_generic.c   |   16 ++++++++++++++++
 net/sched/sch_gred.c      |    1 +
 net/sched/sch_hfsc.c      |   15 ++++-----------
 net/sched/sch_htb.c       |    1 +
 net/sched/sch_multiq.c    |   29 +++++++++++++++++++++++++++++
 net/sched/sch_netem.c     |   15 +++++++--------
 net/sched/sch_prio.c      |   14 ++++++++++++++
 net/sched/sch_red.c       |    9 +++++++++
 net/sched/sch_sfq.c       |   12 ++++++++++++
 net/sched/sch_tbf.c       |   13 ++++++-------
 net/sched/sch_teql.c      |    9 +++++++++
 18 files changed, 175 insertions(+), 31 deletions(-)