On 08/27/2009 03:09 PM, Thomas Gleixner wrote:

That's just the wrong approach. All you need is a way to tell the
kernel that CPUx can switch off the scheduler tick when only one
thread is running and that very thread is running in user space. Once
another thread arrives on that CPU or the single thread enters the
kernel for a blocking syscall the scheduler tick has to be
restarted.

That's an elegant approach...I like it.

How would you deal with per-cpu kernel threads (softirqs, etc.) or
softirq processing while in the kernel?  Switching off the timer tick
isn't sufficient because the scheduler will be triggered on the way back
to userspace in a syscall.

Chris