[dividuum]

I don't see how that would work. The memory access causing the page fault still blocks, but now another thread handles paging in the requested data. So without coordination between those two, nothing really changes. Sounds easier to just use nonblocking reads directly.

Thanks for the pointer to userfaultfd. Didn't know that existed.

[cmrdporcupine]

Yeah. Part of the problem is that userfaultfd isn't itself quite flexible enough. What you might want to do is release the faulted thread to do some other work, letting it "know" what it can come back later when the data is available, but there's no mechanism to make that happen. Instead it's going to be entirely blocked until the fault can be resolved.