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Accepted
Sirajus Salekin
Asked: 2018-06-09 19:25:23 +0800 CST

make zram use lz4 compression algorithm

  • 772

Ubuntu 18, trying to make zram to use lz4 compression.

Tried modifying /usr/bin/init-zram-swapping file

#!/bin/sh
...........
...........
for i in $(seq ${NRDEVICES}); do
  DEVNUMBER=$((i - 1))
  echo $mem > /sys/block/zram${DEVNUMBER}/disksize
  echo lz4 > /sys/block/zram${DEVNUMBER}/comp_algorithm # <= added this line
  mkswap /dev/zram${DEVNUMBER}
  swapon -p 5 /dev/zram${DEVNUMBER}
done

But, after rebootzramctl still shows I'm using lzo algortihm

NAME       ALGORITHM DISKSIZE  DATA  COMPR TOTAL STREAMS MOUNTPOINT
/dev/zram3 lzo           466M  2.9M 614.2K    1M       4 [SWAP]
/dev/zram2 lzo           466M  2.9M 631.2K    1M       4 [SWAP]
/dev/zram1 lzo           466M  2.9M 536.1K 1020K       4 [SWAP]
/dev/zram0 lzo           466M    3M   610K    1M       4 [SWAP]

I also tried adding adding it inrc.local, but it throws device already in use warning, because as far as I know, the change needs to be done before mkswap and swapon runs.

swap compression zram

1 Answers

  1. Best Answer

    This works:

    # initialize the devices
for i in $(seq ${NRDEVICES}); do
  DEVNUMBER=$((i - 1))
  echo lz4 > /sys/block/zram${DEVNUMBER}/comp_algorithm
  echo $mem > /sys/block/zram${DEVNUMBER}/disksize
  mkswap /dev/zram${DEVNUMBER}
  swapon -p 100 /dev/zram${DEVNUMBER}
done

    Note: it seems you need to define the compression algorithm before zram size. Set swapon -p to priority level 100 to use zram actively as it improves performance.

    • 7