[ori_prior]

WSL1 was a dead end, not because of compatibility but because of performance, especially when it comes to file system access and process operations. Windows is supremely complex in both, with things like filesystem filters, fused fork+exec+setuid+setcap+doWindowsStuffThatDoesntHaveUnixEquivalents syscalls, all of which you cannot avoid. If you layer a Linux syscall personality on top of that, things will get molasses-slow quickly.

[monocasa]

To be fair, at least on the syscall side, WSL1 was built in kernel space on Pico Processes, not regular NT processes. They very much were able to avoid the windows cruft. It really seemed to be the long tail on compat and the impedance mismatch on the vfs layer that killed it.

[pjc50]

Correct - the semantics are simply too different to directly emulate. The simple fact that starting processes takes much longer in Windows cripples naive implementations, for example.