The sysctl netdev_max_backlog sets a limit to the maximum number of packets allowed in the kernel's backlog queue.

Is there a way to check the current queue size (i.e., how many packets are currently in the queue at a given time)?

Literally, the value of queue->input_pkt_queue.qlen from net/core/dev.c:netif_rx():

  queue = &__get_cpu_var(softnet_data);

  if (queue->input_pkt_queue.qlen <= netdev_max_backlog) {
    if (queue->input_pkt_queue.qlen) {
      __skb_queue_tail(&queue->input_pkt_queue, skb);
      return NET_RX_SUCCESS;
  • Did you find the answer? Share if yes. I'm here with the same question. – rlib Aug 25 '16 at 7:11
  • nope, i never found out how :( – Christopher Neylan Oct 12 '16 at 0:16
probe kernel.statement("enqueue_to_backlog@net/core/dev.c:3536") {
    printf("probe enqueue_to_backlog on cpu: %d qlen: %d\n", $sd->cpu, $qlen + 1)

systemtap probe. Line number(3536) depends on kernel version, look for this line

if (qlen <= netdev_max_backlog && !skb_flow_limit(skb, qlen)) {

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