Ubuntu runner ext4 filesystem optimization.

[aagmv]

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What GitHub Actions topic or product is this about?

Actions Runner Image

Discussion Details

actions/runner-images#1939 was an issue about optimizing mount options for ubuntu runners. This was closed with a comment requesting more data to justify optimizations.

I am testing on

ubuntu-latest-2cpu-8ram-75ssd
Image: ubuntu-24.04
Version: 20250929.60.1

I saw a sudo rm -r /usr/local/lib/android step taking 4m11s with the default configuration.
Then I changed our workflow and applied sudo mount -o remount,delalloc,noauto_da_alloc,barrier=0,lazytime / before the deletion step. The deletion step then only took 22s.

So 4m11s -> 22s.

I also tried applying data=writeback,journal_async_commit but those options can't be changed without rebooting, so I can't test whether they would provide a benefit on the cloud hardware used by GHA. On my development workstation they do help in some benchmarks.

---

Additionally building the runners with XFS instead of ext4 might provide a benefit for workloads that do a lot of file copying since XFS on modern kernels does support reflink copies while ext4 does not. But this is even more difficult to test since the filesystem can't be converted in-place.

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