Print network soft IRQ back-pressure stats

soft_net.sh

#!/bin/bash

# A variation of:
# https://github.com/majek/dump/blob/master/how-to-receive-a-packet/softnet.sh
# by jwbensley@gmail.com / https://github.com/jwbensley

cmd="${0##*/}"

usage() {
cat >&2 <<EOI
usage: $cmd [ -h ]
Output column definitions:
      cpu  # of the cpu
    total  # of packets (not including netpoll) received by the interrupt handler
             There might be some double counting going on:
                net/core/dev.c:1643: __get_cpu_var(netdev_rx_stat).total++;
                net/core/dev.c:1836: __get_cpu_var(netdev_rx_stat).total++;
             I think the intention was that these were originally on separate
             receive paths ...
  dropped  # of packets that were dropped because netdev_max_backlog was exceeded
 squeezed  # of times ksoftirq ran out of netdev_budget or time slice with work
             remaining
collision  # of times that two cpus collided trying to get the device queue lock.
EOI
        exit 1
}



softnet_stats_header() {
        printf "%3s %10s %10s %10s %10s %10s %10s\n" cpu total dropped squeezed collision rps flow_limit
}

softnet_stats_format() {
        printf "%3u %10lu %10lu %10lu %10lu %10lu %10lu\n" "$1" "0x$2" "0x$3" "0x$4" "0x$5" "0x$6" "0x$7"
}


getopts h flag && usage

cpu=0
softnet_stats_header
while read total dropped squeezed j1 j2 j3 j4 j5 collision rps flow_limit_count
do
        # the last field does not appear on older kernels
        # https://github.com/torvalds/linux/commit/99bbc70741903c063b3ccad90a3e06fc55df9245#diff-5dd540e75b320a50866267e9c52b3289R165
        softnet_stats_format $((cpu++)) "$total" "$dropped" "$squeezed" "$collision" "$rps" "${flow_limit_count:-0}"
done < /proc/net/softnet_stat