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Comment by oblio | Hacker News Reader

NT has had support for "personalities" since its inception. This is not even the first *NIX one it has had :)

Still, I agree that it's an impressive achievement.

Except WSL has little in common with traditional NT personalities. Traditional NT personalities were a false good idea, and have been a failure in the long term, especially to run Unix workloads -- however this jugement is easy with insight -- when it came out traditional NT personalities were quite interesting.

No idea about code commonality, but the broad architecture of WSL is basically the same as the original POSIX personality from the 90's. The "foreign" process runs in a special mode and handles a different set of system calls via a different dispatch mechanism in the kernel, but still on top of the same set of kernel functionality beneath that.

Actually they are using the picoprocess ideas taken from Drawbridge research.

You are partially right, it is just that they improved a few things.

Traditional NT personalities were about the mechanism details.

Otherwise it is very current in operating systems to have a common kernel running different kind of userspace using different API - so of course there are some similarities, but only because it would be completely impossible not to have some.

What was the first?

The first featured one was Interix, which became SFU and then SUA. Picoprocesses (the base block behind WSL) were introduced in Windows 8.1, where SUA was removed (was deprecated in 8.0).

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