Skip to content

zramSwap

Zramswap

zramSwap.algorithm

Compression algorithm. lzo has good compression, but is slow. lz4 has bad compression, but is fast. zstd is both good compression and fast, but requires newer kernel. You can check what other algorithms are supported by your zram device with {command}cat /sys/class/block/zram*/comp_algorithm

Type: one of "842", "lzo", "lzo-rle", "lz4", "lz4hc", "zstd" or string

Default

"zstd"

Example

"lz4"

Declared by: https://github.com/nixos/nixpkgs/blob/master/nixos/modules/config/zram.nix

zramSwap.enable

Enable in-memory compressed devices and swap space provided by the zram kernel module. See https://www.kernel.org/doc/Documentation/blockdev/zram.txt .

Type: boolean

Default

false

Declared by: https://github.com/nixos/nixpkgs/blob/master/nixos/modules/config/zram.nix

zramSwap.memoryMax

Maximum total amount of memory (in bytes) that can be stored in the zram swap devices. This doesn't define how much memory will be used by the zram swap devices.

Type: null or signed integer

Default

null

Declared by: https://github.com/nixos/nixpkgs/blob/master/nixos/modules/config/zram.nix

zramSwap.memoryPercent

Maximum total amount of memory that can be stored in the zram swap devices (as a percentage of your total memory). Defaults to 1/2 of your total RAM. Run zramctl to check how good memory is compressed. This doesn't define how much memory will be used by the zram swap devices.

Type: signed integer

Default

50

Declared by: https://github.com/nixos/nixpkgs/blob/master/nixos/modules/config/zram.nix

zramSwap.priority

Priority of the zram swap devices. It should be a number higher than the priority of your disk-based swap devices (so that the system will fill the zram swap devices before falling back to disk swap).

Type: signed integer

Default

5

Declared by: https://github.com/nixos/nixpkgs/blob/master/nixos/modules/config/zram.nix

zramSwap.swapDevices

Number of zram devices to be used as swap, recommended is 1.

Type: signed integer

Default

1

Declared by: https://github.com/nixos/nixpkgs/blob/master/nixos/modules/config/zram.nix

zramSwap.writebackDevice

Write incompressible pages to this device, as there's no gain from keeping them in RAM.

Type: null or path

Default

null

Example

"/dev/zvol/tarta-zoot/swap-writeback"

Declared by: https://github.com/nixos/nixpkgs/blob/master/nixos/modules/config/zram.nix