[email protected] writes: > From: Tianyu Lan <[email protected]> > > Hyper-V guests use the default native_sched_clock() in pv_ops.time.sched_clock > on x86. But native_sched_clock() directly uses the raw TSC value, which > can be discontinuous in a Hyper-V VM. Add the generic hv_setup_sched_clock() > to set the sched clock function appropriately. On x86, this sets > pv_ops.time.sched_clock to read the Hyper-V reference TSC value that is > scaled and adjusted to be continuous.
Hypervisor can, in theory, disable TSC page and then we're forced to use MSR-based clocksource but using it as sched_clock() can be very slow, I'm afraid. On the other hand, what we have now is probably worse: TSC can, actually, jump backwards (e.g. on migration) and we're breaking the requirements for sched_clock(). -- Vitaly
