Use btrfs with compress to further reduce storage consumption

[RadxaYuntian]

Before I knew this action I was using btrfs with compress to workaround my own space issue. I see this action is still using ext4, so this could be another way to accommodate large projects.

[easimon]

Sounds interesting. Do you have any ballpark figures, how good the compression works and how compression affects CPU usage?

[RadxaYuntian]

In my old action I used zstd compression, and by default btrfs uses compress level 3. Some old benchmark show that it can yield about 42% space saving. Running at full speed zstd is said to consume 20-30% CPU cycles, but such heavy IO operation shouldn't occur too often for normal workflows.

[easimon]

That could be an interesting option for those requiring even more space.

Would you mind creating a merge request with btrfs as an option?

[mirage335]

I would very greatly appreciate this, and can confirm BTRFS compression plays nice with GitHub Actions and 'maximize-build-space'. Since I am already running a compressed BTRFS ChRoot on a loopback image within GitHub Actions after the 'maximize-build-space' step. Yes, the kernels used by GitHub Actions have full support and all.

This would improve my margins from only a few gigabytes, to a several more gigabytes. Compression is a good upwards of 30%-50%, and much, much more importantly, compression eliminates unused disk space from loopback filesystems in which a 'dd if=/dev/zero of=./fill' has been applied recently.

EDIT: You might find relevant code scattered around relevant shell code projects I do some work on...
https://github.com/soaringDistributions/ubDistBuild/blob/main/ubiquitous_bash.sh
https://github.com/mirage335-colossus/ubiquitous_bash/blob/c70169e4e512b07d6699c64339e7bd7e9c5c4d6a/virtualization/bios/createvm.sh

[mirage335]

Looks like this line could change to use btrfs instead of ext4 :

https://github.com/easimon/maximize-build-space/blob/master/action.yml#L176

And this line could enable compression :

https://github.com/easimon/maximize-build-space/blob/master/action.yml#L181

[libenc]

I've made some progress on my fork libenc/maximize-build-space@add-btrfs-support. These changes have actually been running for a while in my private projects brefore this fork and have shown to be stable enough, so I decided to share them out. Since there is already a PR #37 about this issue, I'll wait for some feedback, and add some docs related if needed.

As turning on the compression with BTRFS may have a large performance impact and also for compatibility reasons, an option has been added to explicitly turn on the BTRFS (use-btrfs) and provide options for tuning the compression algorithm and levels. So these changes will not have an unexpected impact on existing users.