Draw a sparkline of dirty pages over time on Linux.

watch-spark-dirty-pages.sh

#!/bin/bash
set -e
set -o pipefail

statefile="$(mktemp --tmpdir=/run spark-dirty-pages.XXXXX)"
trap 'rm -f $statefile' INT HUP QUIT

function watch_iter {
  declare -a dirty
  readarray -t dirty < "$statefile"

  dirty+=( "$(grep Dirty /proc/meminfo | awk '{print $2 "K";}' | numfmt --from=iec)" )
  declare -i trimstart
  (( trimstart = ${#dirty[@]} - COLUMNS ))
  if (( trimstart < 0 )); then
    trimstart=0
  fi
  dirty=( "${dirty[@]:$trimstart:$COLUMNS}" )

  # Flush the state file
  printf "%s\n" "${dirty[@]}" > "$statefile"

  echo "Dirty: $(numfmt --to=iec --suffix=B ${dirty[-1]})"
  # https://github.com/holman/spark
  spark <<< "${dirty[@]}"
}

export -f watch_iter
export statefile

watch -ex "$@" -- "$BASH" -c watch_iter