From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stephen Hemminger Subject: Re: [PATCH 04/14] sch_netem: Use requeue list instead of ops->requeue() Date: Tue, 14 Oct 2008 08:22:35 -0700 Message-ID: <20081014082235.10b46637@extreme> References: <20081014095349.GE10804@ff.dom.local> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: David Miller , netdev@vger.kernel.org To: Jarek Poplawski Return-path: Received: from mail.vyatta.com ([76.74.103.46]:45491 "EHLO mail.vyatta.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751276AbYJNPWk (ORCPT ); Tue, 14 Oct 2008 11:22:40 -0400 In-Reply-To: <20081014095349.GE10804@ff.dom.local> Sender: netdev-owner@vger.kernel.org List-ID: On Tue, 14 Oct 2008 09:53:49 +0000 Jarek Poplawski wrote: > -------- Original Message -------- > Subject: [PATCH 5/9]: sch_netem: Use requeue list instead of ops->requeue() > Date: Mon, 18 Aug 2008 01:37:02 -0700 (PDT) > From: David Miller > > ---------------> > From: David Miller > sch_netem: Use requeue list instead of ops->requeue() > > This code just wants to make this packet the "front" one, and that's > just as simply done by queueing to the ->requeue list. > > Signed-off-by: Jarek Poplawski > --- > net/sched/sch_netem.c | 11 +++-------- > 1 files changed, 3 insertions(+), 8 deletions(-) > > diff --git a/net/sched/sch_netem.c b/net/sched/sch_netem.c > index cc4d057..5ca92d9 100644 > --- a/net/sched/sch_netem.c > +++ b/net/sched/sch_netem.c > @@ -233,7 +233,8 @@ static int netem_enqueue(struct sk_buff *skb, struct Qdisc *sch) > */ > cb->time_to_send = psched_get_time(); > q->counter = 0; > - ret = q->qdisc->ops->requeue(skb, q->qdisc); > + __skb_queue_tail(&q->qdisc->requeue, skb); > + ret = NET_XMIT_SUCCESS; > } > > if (likely(ret == NET_XMIT_SUCCESS)) { > @@ -295,13 +296,7 @@ static struct sk_buff *netem_dequeue(struct Qdisc *sch) > return skb; > } > > - if (unlikely(q->qdisc->ops->requeue(skb, q->qdisc) != NET_XMIT_SUCCESS)) { > - qdisc_tree_decrease_qlen(q->qdisc, 1); > - sch->qstats.drops++; > - printk(KERN_ERR "netem: %s could not requeue\n", > - q->qdisc->ops->id); > - } > - > + __skb_queue_tail(&q->qdisc->requeue, skb); > qdisc_watchdog_schedule(&q->watchdog, cb->time_to_send); > } > This won't work for the case where time based reordering changes the packet sent. The current code works like this: Packet marked to be sent at some time (+101ms) new packet is queued and the random delay computes smaller delta (+87ms) new packet will go out in first. This was done for compatibility with NISTnet, so research that wanted to reproduce NISTnet results could use netem.