On Thu, Mar 01, 2007 at 06:54:24PM -0800, Zachary Amsden wrote:

The custom_sched_clock hook is broken.  The result from sched_clock needs to be
in nanoseconds, not in CPU cycles.  The TSC is insufficient for this purpose,
because TSC is poorly defined in a virtual environment, and mostly represents
real world time instead of scheduled process time (which can be interrupted
without notice when a virtual machine is descheduled).

To make the scheduler consistent, we must expose a different nature of time,
that is scheduled time.  So deprecate this custom_sched_clock hack and turn it
into a paravirt-op, as it should have been all along.  This allows the tsc.c
code which converts cycles to nanoseconds to be shared by all paravirt-ops
backends.

It is unfortunate to add a new paravirt-op, but this is a very distinct
abstraction which is clearly different for all virtual machine implementations,
and it gets rid of an ugly indirect function which I ashamedly admit I hacked
in to try to get this to work earlier, and then even got in the wrong units.

Please apply.

I think it's better to remove this completely and not allow paravirt
to hook into sched_clock.  After all a hypervisor stealing time is no
different from interrupts stealing time and we don't try to handle
that either. 

I will remove the custom hook.

-Andi