sonic-buildimage/files/initramfs-tools/modules
Samuel Angebault fa95ebcaae Add optional zram compression for docker_inram
Some devices running SONiC have a small storage device (2G and 4G mainly)
The SONiC image growth over time has made it impossible to install
2 images on a single device.
Some mitigations have been implemented in the past for some devices but
there is a need to do more.

One such mitigation is `docker_inram` which creates a `tmpfs` and
extracts `dockerfs.tar.gz` in it.
This all happens in the SONiC initramfs and by ensuring the installation
process does not extract `dockerfs.tar.gz` on the flash but keep the file as is.

This mitigation does a tradeoff by using more RAM to reduce the disk footprint.
It however creates new issues for devices with 4G of system memory since
the extracted `dockerfs.tar.gz` nears the 1.6G.
Considering debian upgrades (with dual base images) and the continuous
stream of features this is only going to get bigger.

This change introduces an alternative to the `tmpfs` by allowing a system
to extract the `dockerfs.tar.gz` inside a `zram` device thus bringing
compression in play at the detriment of performance.

Introduce 2 new optional kernel parameters to be consumed by SONiC initramfs.
 - `docker_inram_size` which represent the max physical size of the
   `zram` or `tmpfs` volume (defaults to DOCKER_RAMFS_SIZE)
 - `docker_inram_algo` which is the method to use to extract the
   `dockerfs.tar.gz` (defaults to `tmpfs`)
   other values are considered to be compression algorithm for `zram`
   (e.g `zstd`, `zlo-rle`, `lz4`)

Refactored the logic to mount the docker fs in the SONiC initramfs under
the `union-mount` script.
Moved the code into a function to make it cleaner and separated the
inram volume creation and docker extraction.

On Arista platform with a flash smaller or equal to 4GB set
`docker_inram_algo` to `zstd` which produces the best compression ratio
at the detriment of a slower write performance and a similar read
performance to other `zram` compression algorithms.
2023-05-18 14:21:52 -07:00

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squashfs
overlay
vfat
nls_ascii
nls_cp437
nls_utf8
nvme
zstd