On Thu, May 15, 2014 at 02:17:11PM +0200, Juan Quintela wrote: > Eduardo Habkost <[email protected]> wrote: > > From: Marcelo Tosatti <[email protected]> > > > > Invariant TSC documentation mentions that "invariant TSC will run at a > > constant rate in all ACPI P-, C-. and T-states". > > > > This is not the case if migration to a host with different TSC frequency > > is allowed, or if savevm is performed. So block migration/savevm. > > > > Cc: Juan Quintela <[email protected]> > > Signed-off-by: Marcelo Tosatti <[email protected]> > > Reviewed-by: Eduardo Habkost <[email protected]> > > Signed-off-by: Eduardo Habkost <[email protected]> > > Reviewed-by: Juan Quintela <[email protected]> > > I don't have a better suggestion. Really we could allow migration to > identical machines, but I assume that there is not a way to read the tsc > frequency? > (Althought reading the model name/numbers could be enough?)
Even if migration to identical machine is performed, you would have to perform timing of downtime to compensate. > I.e. Add a subsection that includes the cpu model name, or whatever we > can have to identify the host cpu? "On processors with invariant TSC support, the OS may use the TSC for wall clock timer services (instead of ACPI or HPET timers)."
