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#!/bin/bash
# This script does the following:
# zramswap start:
# * Space is assigned to each zram device, then swap is initialized on
# there
# zramswap stop:
# * Undo start
# * Also attempts to remove zram module at the end
# TODO:
# * Migrate to using zramctl from util-linux for the setup,
# (this will close debian bug #917643):
# then also:
# - add option for compression algorythm
# - ammount of compression streams
# - Make use of the zramctl stats too
function start {
#Set some defaults:
ALLOCATION=256 # ZRAM Swap you want assigned, in MiB
PRIORITY=100 # Swap priority, see swapon(2) for more details
# Get amount of available CPU cores, set to 1 if not detected correctly
if [ ! -f /proc/cpuinfo ]; then
echo "WARNING: Can't find /proc/cpuinfo, is proc mounted?"
echo " Using a single core for zramswap..."
CORES=1
else
CORES=$(grep -c ^processor /proc/cpuinfo)
fi
# Override above from config file, if it exists
if [ -f /etc/default/zramswap ]; then
. /etc/default/zramswap
fi
ALLOCATION=$((ALLOCATION * 1024 * 1024)) # convert amount from MiB to bytes
if [ -n "$PERCENTAGE" ]; then
totalmemory=$(awk '/MemTotal/{print $2}' /proc/meminfo) # in KiB
ALLOCATION=$((totalmemory * 1024 * $PERCENTAGE / 100))
fi
# Initialize zram devices
modprobe zram num_devices=$CORES
# Assign memory to zram devices, initialize swap and activate
# Decrementing $CORE, because cores start counting at 0
for CORE in $(seq 0 $(($CORES - 1))); do
echo $(($ALLOCATION / $CORES)) > /sys/block/zram$CORE/disksize
mkswap /dev/zram$CORE
swapon -p $PRIORITY /dev/zram$CORE
done
}
function status {
orig_data_size="0"
for file in /sys/block/zram*/*_data_size ; do
if [ $file = "/sys/block/zram*/*_data_size" ]; then
compress_ratio="0"
break
fi
read file_content < $file
what=$(basename $file)
eval "$what=\$(($what + $file_content))"
compress_ratio=$(echo "scale=2; $orig_data_size / $compr_data_size" | bc)
done
echo "compr_data_size: $((compr_data_size / 1024)) KiB"
echo "orig_data_size: $((orig_data_size / 1024)) KiB"
echo "compression-ratio: $compress_ratio"
}
function stop {
for swapspace in $(swapon -s | awk '/zram/{print $1}'); do
swapoff $swapspace
done
modprobe -r zram
}
function usage {
echo "Usage:"
echo " zramswap start - start zram swap"
echo " zramswap stop - stop zram swap"
echo " zramswap status - prints some statistics"
}
if [ "$1" = "start" ]; then
start
fi
if [ "$1" = "stop" ]; then
stop
fi
if [ "$1" = "status" ]; then
status
fi
if [ "$1" = "" ]; then
usage
fi
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