Messages in this thread | | | Date | Wed, 07 Jan 2015 11:59:00 -0500 | From | Boris Ostrovsky <> | Subject | Re: [PATCH RFC] xen-time: decreasing the rating of the xen clocksource below that of the tsc clocksource for dom0's |
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On 01/07/2015 11:16 AM, Imre Palik wrote: > From: "Palik, Imre" <imrep@amazon.de> > > In Dom0's the use of the TSC clocksource (whenever it is stable enough to > be used) instead of the Xen clocksource should not cause any issues, as > Dom0 VMs never live-migrated. The TSC clocksource is somewhat more > efficient than the Xen paravirtualised clocksource, thus it should have > higher rating. > > Cc: Anthony Liguori <aliguori@amazon.com> > Signed-off-by: Imre Palik <imrep@amazon.de> > --- > arch/x86/xen/time.c | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/arch/x86/xen/time.c b/arch/x86/xen/time.c > index f473d26..c768726 100644 > --- a/arch/x86/xen/time.c > +++ b/arch/x86/xen/time.c > @@ -487,6 +487,10 @@ static void __init xen_time_init(void) > int cpu = smp_processor_id(); > struct timespec tp; > > + /* As Dom0 is never moved, no penalty on using TSC there */ > + if (xen_initial_domain()) > + xen_clocksource.rating = 275;
Should this only be limited to dom0? Can we do this for guests running with TSC_MODE_NEVER_EMULATE as well?
We also have disable_migrate flag for guests (but it doesn't appear to be accessible to a guest kernel).
-boris
> + > clocksource_register_hz(&xen_clocksource, NSEC_PER_SEC); > > if (HYPERVISOR_vcpu_op(VCPUOP_stop_periodic_timer, cpu, NULL) == 0) {
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