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 _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxx https://lists.osdl.org/mailman/listinfo/virtualization
