But that's not what SA was about. Even with N:N architecture, if one kernel thread blocks (say, on I/O), the point is for the user-space scheduler to decide wh

But that's not what SA was about. Even with N:N architecture, if one kernel thread blocks (say, on I/O), the point is for the user-space scheduler to decide which thread should run next. The point was that the kernel scheduler cannot/should not understand the application thread scheduling requirements, and that when a kernel thread allocated to the task blocks, only user space can (correctly) decide what to do.