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Comment by scandinavian | Hacker News Reader

Accessing the Windows filesystem from WSL and vice versa is extremely slow, so running for example your IDE in WSL and having your code etc. stored in WSL is useful. I think that is one of the big usecases. It's already kinda supported in vscode, where it runs a vscode server in WSL and Windows just runs the frontend.

It's useful for me when developing dotnet intended for Linux as I can store the code in WSL and be able to build, debug, run docker and so on directly from vscode.

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Why is it so slow? I use VMware player and swapping files is fine. WSL2 seems like it's just using a lightweight VM over HyperV... is Hyper V really that much worse than VMware (and VBox) in this?

WSL2 uses 9P (of the venerable Plan 9 pedigree, I assume because Erick Smith is a nerd!) to remote the filesystems. I don't think that's part of HyperV (though it could be a custom VSP/VSC, and that channel is ridiculously slow.)

Personally I haven't run into slowness other than Windows sucking at copying lots of small files, which is NT's fault for allowing FS filter drivers and their ridiculous locking scheme.

Are you talking about WSL1 or WSL? Wsl2 is much much faster due to having a virtualized real linux kernel running

Accessing the WSL filesystem from WSL is indeed a lot faster on WSL2. Accessing the Windows filesystem from WSL or vise versa is even slower in WSL2 compared to WSL1.

https://docs.microsoft.com/en-us/windows/wsl/compare-version...

> As you can tell from the comparison table above, the WSL 2 architecture outperforms WSL 1 in several ways, with the exception of performance across OS file systems.

System performance is, IO between Windows and Linux isn’t.

https://github.com/microsoft/WSL/issues/4197

WSL2 disk access from the Windows side is very slow. It's the reciprocal problem of WSL1.

WSL2 Linux apps now get proper performance now but if your IDE is on the Windows side, access time to project files on native Linux partition is terrible.

...actually e.g. VS Code has a really great split backend, so you can actually have the frontend "properly" on Windows anyway, and yet still use WSL2.

My own case was something different: annoyingly configured automated browser tests with Cypress. Just running them inside WSL and letting that start a browser on the distro itself was the most comfortable way to debug these.

But I mean come on, they're Microsoft. If they really wanted filesystem access to be efficient across systems, we'd have it by now. Although convenient, I doubt that's on their list of primary motivations for doing this.

>But I mean come on, they're Microsoft. If they really wanted filesystem access to be efficient across systems, we'd have it by now.

Here's one of the developers saying it is hard back in the WSL days.

https://github.com/Microsoft/WSL/issues/873#issuecomment-391...

The reason makes sense to me, but I'm not an expert. Maybe you could expand on why you think they could do it but chose not to?

Seeing how every file system (NTFS) imrovement since windows 7 (like new compression methods) is done in layers running on top of ntfs. I think that Microsoft has either lost the source to ntfs driver or institutional knowledge of how it works.

The real answer is that they're building filters on top of NTFS because that's precisely how it was designed to work.

GP's explanation was almost as plausible, and much funnier.

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