"Threads" are nothing but kernel-mode coroutines with purpose-built schedulers in the kernel.
Redoing the same machinery except in usermode is not the way to get performance.
The problem is that scripting languages don't let you access the kernel API's cleanly due to various braindead design decisions - global locks in the garbage collector, etc.
But the solution isn't to rewrite the kernel in every scripting language, the solution is to learn to make scripting languages that aren't braindead.
"Threads" are nothing but kernel-mode coroutines with purpose-built schedulers in the kernel.
Redoing the same machinery except in usermode is not the way to get performance.
The problem is that scripting languages don't let you access the kernel API's cleanly due to various braindead design decisions - global locks in the garbage collector, etc.
But the solution isn't to rewrite the kernel in every scripting language, the solution is to learn to make scripting languages that aren't braindead.