> I can't see how a userland implementation can have better performances > than an all in-kernel implementation. There are more context switches, > which are notr so cheap with Xen.
>From what I understand using blktap with Xen provides better performance because it is designed specifically for this task (attach disks to virtual machines), and uses asynchronous I/O, not because it's implemented in userspace (if the whole thing was implemented inside the kernel it will of course be faster, but it would also be more dangerous regarding the security of the Dom0).
