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zram.md

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Zram

Description

zram, formerly called compcache, is a Linux kernel module for creating a compressed block device in RAM, i.e. a RAM disk with on-the-fly disk compression. The block device created with zram can then be used for swap or as general-purpose RAM disk.

Directory

References

Setup

Important

Parts of this guide assumes that you are using the BTRFS filesystem and GRUB.

Description

This details how to setup Zram to be used as an alternative to swap.

References

Steps

  1. First and foremost, ensure that swap is currently disabled:

    inxi -j

    Sample output:

    Swap:
Alert: No swap data was found.

    If swap is enabled, disable it first.

  2. Install the zram-generator package using yay.

  3. Prepare a zram-generator config:

    Create the config file:

    sudo nano /etc/systemd/zram-generator.conf

    Sample content of the config:

    [zram0]
zram-size = ram / 2
compression-algorithm = zstd
swap-priority=60

    [!TIP]
    This sets the zram-size to half of your total system memory. To set it to full, set the value to ram.

    [!TIP]
    The swap-priority variable is optional and can be set from -1 (lowest priority) to 32767 (highest priority). This variable defaults to 100 if not set.

  4. Reload and start the relevant services:

    • Reload the systemd manager configuration:

      sudo systemctl daemon-reload

    • Start the Zram service we had configured (i.e. /dev/zram0).

  5. Disable Zswap for maximum efficiency with using Zram:

    • Update the GRUB file:

      sudo nano /etc/default/grub

    • Locate the GRUB_CMDLINE_LINUX_DEFAULT variable in the file.

      Sample content:

      GRUB_CMDLINE_LINUX_DEFAULT='nowatchdog nvme_load=YES loglevel=3'

    • Add the zswap.enabled=0 parameter to the end of the value of the GRUB_CMDLINE_LINUX_DEFAULT variable.

      Sample content:

      GRUB_CMDLINE_LINUX_DEFAULT='nowatchdog nvme_load=YES loglevel=3 zswap.enabled=0'

    • Save the file.

  6. Regenerate a new GRUB config so our changes to GRUB apply in the next boot.

  7. Restart the system.

  8. Verify our changes:

    • Verify Zram has been enabled:

      inxi -j
sudo dmesg | grep zram

      Sample output:

      Swap:
ID-1: swap-1 type: zram size: 7.66 GiB used: 2.44 GiB (31.9%)
    dev: /dev/zram0
      [    3.471553] zram: Added device: zram0
[    3.753380] systemd[1]: Created slice Slice /system/systemd-zram-setup.
[    3.760467] systemd[1]: Expecting device /dev/zram0...
[    4.857465] zram0: detected capacity change from 0 to 16072704
[    5.057472] Adding 8036348k swap on /dev/zram0.  Priority:60 extents:1 across:8036348k SSDsc

    • Verify Zswap has been disabled:

      sudo dmesg | grep zswap

      Sample output:

      [    0.000000] Command line: BOOT_IMAGE=/@/boot/vmlinuz-linux-lts root=UUID=bzxd1bo8-9nnb-ddet-qykk-qjdgr9yytybg rw rootflags=subvol=@ nowatchdog nvme_load=YES loglevel=3 zswap.enabled=0
[    0.046053] Kernel command line: BOOT_IMAGE=/@/boot/vmlinuz-linux-lts root=UUID=bzxd1bo8-9nnb-ddet-qykk-qjdgr9yytybg rw rootflags=subvol=@ nowatchdog nvme_load=YES loglevel=3 zswap.enabled=0