Re: [Xen-devel] [PATCH] xen: always set the sched clock as unstable

[David Vrabel <david.vrabel@xxxxxxxxxx>]

On 16/04/12 17:05, Dan Magenheimer wrote:
>> From: David Vrabel [mailto:david.vrabel@xxxxxxxxxx]
>> Subject: Re: [Xen-devel] [PATCH] xen: always set the sched clock as unstable
> 
> Nacked-by: Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>

Fair enough,

> [A stable clock] should be true for Xen 4.0+ (but not for pre-Xen-4.0).

The original customer problem is on a host with Xen 3.4.  What do you
recommend for Linux guests running such hosts?

> In fact, it might be wise for a Xen-savvy kernel to check to see
> if it is running on Xen-4.0+ and, if so, force clocksource=tsc
> and tsc=reliable.

So, should the xen clocksource do:

if Xen 4.0+
    clock is stable, use rdtsc only.
else
    clock is unstable, use existing pvclock implementation.

David

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