[hapless]

As I understand it, it's not really possible to "improve" Win32 I/O performance -- both the fundamental I/O APIs and the NTFS on-disk storage format make high performance infeasible.

Not without either abandoning all extant FS drivers, or abandoning NTFS compatibility, anyway.

Edit: Here are the WSL 1.x's team members original comments on this subject. It sounds like a deeply intractable problem.

https://github.com/microsoft/WSL/issues/873#issuecomment-424...

https://github.com/microsoft/WSL/issues/873#issuecomment-425...

The second link explains why a dentry cache just isn't feasible.

The short version is that the NT IO APIs seem to have been very, very ill-considered. It's just not possible to make it fast. Even win32 operations are extremely slow, so win32 applications go out of their way to avoid doing any file I/O. Linux applications were not written with those constraints in mind.

[dblohm7]

Amusingly enough, I just watched a talk about this topic earlier today:

https://www.youtube.com/watch?v=qbKGw8MQ0i8