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x86/xen: prefer TSC over xen clocksource for dom0 

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.

This patch decreases the rating of the Xen clocksource in Dom0s to 275.
Which is half-way between the rating of the TSC clocksource (300) and the
hpet clocksource (250).

Cc: Anthony Liguori <aliguori@amazon.com>
Signed-off-by: Imre Palik <imrep@amazon.de>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>
This commit is contained in:
Palik, Imre 2015-01-13 09:14:22 +01:00 committed by David Vrabel
parent 35c8ab4c5c
commit 94dd85f6a0
1 changed files with 4 additions and 0 deletions
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4
arch/x86/xen/time.c
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@ -479,6 +479,10 @@ static void __init xen_time_init(void)
int cpu = smp_processor_id(); int cpu = smp_processor_id();
struct timespec tp; struct timespec tp;
/* As Dom0 is never moved, no penalty on using TSC there */
if (xen_initial_domain())
xen_clocksource.rating = 275;
clocksource_register_hz(&xen_clocksource, NSEC_PER_SEC); clocksource_register_hz(&xen_clocksource, NSEC_PER_SEC);
if (HYPERVISOR_vcpu_op(VCPUOP_stop_periodic_timer, cpu, NULL) == 0) { if (HYPERVISOR_vcpu_op(VCPUOP_stop_periodic_timer, cpu, NULL) == 0) {