#!/bin/bash

TOTAL_MB=100
TOTAL_BYTES=$((TOTAL_MB << 20))
ROOT_CG=/sys/fs/cgroup
ZRAM_DEV=/dev/zram0
TMPFS=./tmpfs
A_ASCII=$(printf '%d' "'A")

function cleanup() {
  rm -rf $TMPFS/*
  umount $TMPFS
  rmdir $TMPFS

  if swapon -s | grep -q $ZRAM_DEV; then
    swapoff $ZRAM_DEV
  fi
  echo 1 > /sys/block/zram0/reset

  rmdir $ROOT_CG/test
}
trap cleanup EXIT

echo 1 > /sys/module/zswap/parameters/shrinker_enabled

# Initialize tmpfs
mkdir $TMPFS
mount -t tmpfs none $TMPFS

# Initialize zram
echo $((TOTAL_MB*2))m > /sys/block/zram0/disksize
mkswap -L zram0 $ZRAM_DEV
swapon $ZRAM_DEV

# Initialize cgroup
echo "+memory" > $ROOT_CG/cgroup.subtree_control
mkdir $ROOT_CG/test

# Create a test tmpfs file containing the alphabet on repeat
(
  echo 0 > $ROOT_CG/test/cgroup.procs
  s=$(printf '%s' {A..Z})
  yes $s | dd iflag=fullblock of=$TMPFS/test bs=1M count=$TOTAL_MB status=none
)

# Reclaim everything (invoking the zswap shrinker)
echo $TOTAL_BYTES > $ROOT_CG/test/memory.reclaim