Those sinusoids come from a test module inserted in the kernel.

The tool has another test module that monitors the sum of all traffic from all ethernet devices. The tool also has a packet transmit function. The following plot is the result of the dev traffic history while two transmit commands have been requested, a bursty flow first, then a continuous flow.

Last, the first official use of the tool, the qdisc monitoring, note that no tc modification is necessary to use the spy qdisc as follows: (the spy qdisc module must be inserted):

 
  CLASS="class add dev $DEV parent"
  QDISC="qdisc add dev $DEV parent"
  FILTER="filter add dev $DEV parent 1:0 protocol all u32 match u32"

  tc qdisc delete root dev $DEV 1>/dev/null 2>&1
  tc qdisc add dev $DEV root handle 1: hfsc
  tc $CLASS 1:   classid 1:1  hfsc ls rate $max_rate    ul rate $max_rate
  tc $CLASS 1:1  classid 1:10 hfsc ls rate $shared_rate ul rate $max_rate
  tc $CLASS 1:1  classid 1:20 hfsc ls rate $shared_rate ul rate $max_rate
  tc $CLASS 1:10 classid 1:11 hfsc sc umax $umax_11 dmax $dmax_11 rate $rate_11 ul rate $max_rate
  tc $CLASS 1:10 classid 1:12 hfsc sc umax $umax_12 dmax $dmax_12 rate $rate_12 ul rate $max_rate

  tc $QDISC 1:11 handle 11: spy
  tc $QDISC 11:0 handle 111: bfifo limit $qsize

  tc $QDISC 1:12 handle 22: spy
  tc $QDISC 22:0 handle 222: bfifo limit $qsize

  tc $FILTER 0x00000000 0x00800000 at 0 flowid 1:11
  tc $FILTER 0x00800000 0x00800000 at 0 flowid 1:12
 

The tx is configured to give continuous flow in spy qdisc 11 and bursty in spy qdisc 22.

For our test, we choose Blue = dequeue of the continuous flow, Green = dequeue of the bursty flow, Pink = drops of the bursty flow.

For our test, we choose 10ms kernel variable collect period, 100ms plot refresh and 1000 stored samples.

The refresh is fast, the photo cut the top of the plots. Note that the 25 packets in the yellow cursor is for the 10milli-seconde kernel sampling period.