On 13/01/15 15:42, Boris Ostrovsky wrote: > On 01/13/2015 04:52 AM, David Vrabel wrote: >> On 13/01/15 08:14, Imre Palik wrote: >>> From: "Palik, Imre" <im...@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. >>> >>> 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). >> I'm happy with this but would like to see acks from those who objected >> to v1. >> >> David >> >>> --- 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 */ > > Again, why not any PV guest with TSC_MODE_NEVER_EMULATE?
Surely if TSC_MODE_NEVER_EMULATE is set then the TSC is /not/ stable across a guest save/restore thus the PV clocksource must be used? I don't think we want to assume that TSC_MODE_NEVER_EMULATE => never migrate. David _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org http://lists.xen.org/xen-devel
