OverlayFS performance

[l2nkxk8z]

is it true that FUSE-overlayFS has performance implications and may cause stuttering, other performance issues in games?

[cookesan]

Yes, it is possible, but I would phrase it as workload-dependent overhead rather than guaranteed stutter.

FUSE-overlayfs runs the overlay through a userspace filesystem layer. Compared with direct files, and often compared with kernel overlayfs, that can add CPU/latency overhead. Games that stream many assets or do lots of small-file reads are the kind of workload where that overhead can show up as longer loads or occasional hitching. If the game mostly reads large files and they are already cached, you may not notice it.

For Barnacle specifically, the current source points in that direction but does not prove that every game run is already going through FUSE-overlayfs:

nix/package.nix includes fuse-overlayfs as a runtime-related input
barnacle-lib depends on damascus with the overlayfs feature
the generic deployer is shaped around OverlayFs::new(...) and mount/unmount
the generic deployer setup/module path still looks unfinished/commented

So I would not read the repo as "Barnacle will definitely make games stutter." I would read it as "if the final deployment mode uses FUSE-overlayfs, benchmark the games that stream heavily."

A practical test is to compare the same game/profile with direct/native files versus the overlay path, once after a cold cache and once after a warm cache. If the hitching only appears on the overlay path, then it is a plausible deployment tradeoff rather than a general game issue.