Can i use dev_queue_xmit()

Can i use dev_queue_xmit()

[K.Anantha Kiran]

 
Hi,
 
 	We are printing the return value of dev_queue_xmit() and we 
 confirm that this will be NET_XMIT_DROP for dropped pkts.
 
 	in *dev_queue_xmit()* function , there is a call to  *enqueue()* 
 which is function pointer pointing to, /net/sched/sch_generic.c 
 pfifo_fast_enqueue() function. In this if the length of queue is greater 
 that the txqueuelen( a parameter of NIC ) then the packet is not queued 
 and DROPPED.
  
 static int pfifo_fast_enqueue(struct sk_buff *skb, struct Qdisc* qdisc)
     {
 	
 		struct sk_buff_head *list;
    
             list = ((struct sk_buff_head*)qdisc->data) +
                    prio2band[skb->priority&TC_PRIO_MAX];
    
             if (list->qlen <= qdisc->dev->tx_queue_len) {
                     __skb_queue_tail(list, skb);
                     qdisc->q.qlen++;
                     return 0;
             }
             qdisc->stats.drops++;
             kfree_skb(skb);
             return NET_XMIT_DROP;
    }
 
 	We have tested this by printing the values of list->qlen and 
 checking for different values of txqueuelen ( def-100 upto 100000). still 
 the packets are being dropped after some time when the condition fails. 
 and this is continuing until the whole queue is empty, after this it is 
 again resuming to Xmit properly, this phenomenon is repeated.Actually we 
sending 10 lakh pkts at 500 Mbps speed.  
 
 	The problem is that " is there any flag that tell the queue is 
 full and once it is full it will not take any pkts in and drops all 
 till the queue is empty". If so can u plz suggest a solution to this 
 problem.
 
 
 thanks,
 Ananth.

Re: Can i use dev_queue_xmit()

[K.Anantha Kiran]

Hi,

  Sorry, we did not put our question in correct way. 
  We came to know that whenever qdisc is full some flag is set and
it will be unset only when qdisc is completely empty once again.
  Because of this we are unable to enque packets in the qdisc even when 
some space is available. What i want is to enqueue packets as soon as 
qdisc has space for atleast one packet.
  Even if i am increasing the qdisc length, then also after some time
again the qdisc is getting full and packets are getting dropped.

 Note: I am using gigabit ethernet cards.

 Please help me in this matter.

Thanks in advance,
Regards,
Ananth.


On Mon, 12 Apr 2004, Anupam wrote:

> Date: Mon, 12 Apr 2004 14:16:43 +0530
> From: Anupam <anupamg@iitk.ac.in>
> To: K.Anantha Kiran <ananth@cse.iitk.ac.in>
> Subject: Re: Can i use dev_queue_xmit()
> 
> K.Anantha Kiran wrote:
> >  	The problem is that " is there any flag that tell the queue is 
> >  full and once it is full it will not take any pkts in and drops all 
> >  till the queue is empty". If so can u plz suggest a solution to this 
> >  problem.
> 
> 
> Hi Anantha,
> 
>  From above description of yours, I presume that you're trying something 
> that is called "Flush Queue", i.e., when a queue is overloaded, there is 
>   option to drop all packets in queue. This means that all the adaptive 
> flow should back-off. However it is quite inefficient since all the 
> backed-off flows will startup again.
> 
> Anyways, I didn't get the chance to dig up the code myself, but my guess 
> is that solution for you lies in: linux/net/sched/cls_api.c.
> 
> 
> >  thanks,
> >  Ananth.
> 
> 
> Please do let me know how things go.
> 
> Regards,
> 
> Anupam Gupta, Ph.D.
> mailto:anupamg@iitk.ac.in
> Deptt. of EE,
> Res. E1-315, Hall-4
> IIT Kanpur.
> 

Re: Can i use dev_queue_xmit()

[James Stevenson]

Thats 2 off topic posts i count on this.

linux-c-programming is userspace releated you might want
to try the linux-kernel list or the kernelnewbies list

	James

On Mon, 12 Apr 2004, K.Anantha Kiran wrote:

> Hi,
> 
>   Sorry, we did not put our question in correct way. 
>   We came to know that whenever qdisc is full some flag is set and
> it will be unset only when qdisc is completely empty once again.
>   Because of this we are unable to enque packets in the qdisc even when 
> some space is available. What i want is to enqueue packets as soon as 
> qdisc has space for atleast one packet.
>   Even if i am increasing the qdisc length, then also after some time
> again the qdisc is getting full and packets are getting dropped.
> 
>  Note: I am using gigabit ethernet cards.
> 
>  Please help me in this matter.
> 
> Thanks in advance,
> Regards,
> Ananth.
> 
> 
> On Mon, 12 Apr 2004, Anupam wrote:
> 
> > Date: Mon, 12 Apr 2004 14:16:43 +0530
> > From: Anupam <anupamg@iitk.ac.in>
> > To: K.Anantha Kiran <ananth@cse.iitk.ac.in>
> > Subject: Re: Can i use dev_queue_xmit()
> > 
> > K.Anantha Kiran wrote:
> > >  	The problem is that " is there any flag that tell the queue is 
> > >  full and once it is full it will not take any pkts in and drops all 
> > >  till the queue is empty". If so can u plz suggest a solution to this 
> > >  problem.
> > 
> > 
> > Hi Anantha,
> > 
> >  From above description of yours, I presume that you're trying something 
> > that is called "Flush Queue", i.e., when a queue is overloaded, there is 
> >   option to drop all packets in queue. This means that all the adaptive 
> > flow should back-off. However it is quite inefficient since all the 
> > backed-off flows will startup again.
> > 
> > Anyways, I didn't get the chance to dig up the code myself, but my guess 
> > is that solution for you lies in: linux/net/sched/cls_api.c.
> > 
> > 
> > >  thanks,
> > >  Ananth.
> > 
> > 
> > Please do let me know how things go.
> > 
> > Regards,
> > 
> > Anupam Gupta, Ph.D.
> > mailto:anupamg@iitk.ac.in
> > Deptt. of EE,
> > Res. E1-315, Hall-4
> > IIT Kanpur.
> > 
> 
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