From 94dd85f6a0688245dbb5a452a86a2a545dee96c1 Mon Sep 17 00:00:00 2001 From: "Palik, Imre" Date: Tue, 13 Jan 2015 09:14:22 +0100 Subject: [PATCH] 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 Signed-off-by: Imre Palik Signed-off-by: David Vrabel --- 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 69087341d9ae..55da33b1d51c 100644 --- a/arch/x86/xen/time.c +++ b/arch/x86/xen/time.c @@ -479,6 +479,10 @@ 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; + clocksource_register_hz(&xen_clocksource, NSEC_PER_SEC); if (HYPERVISOR_vcpu_op(VCPUOP_stop_periodic_timer, cpu, NULL) == 0) { -- 2.11.0