Re: [Xen-devel] Re: [PATCH] x86: unconditionally mark TSC unstable under Xen

[Jed Smith <jed@xxxxxxxxxx>]

On Jul 14, 2010, at 5:36 PM, Jeremy Fitzhardinge wrote:

> On 07/14/2010 12:24 PM, Jed Smith wrote:
>> Jeremy, Jan - what do you think?  Is this a bad move?  I feel like there
>> is a consequence to this that I am unaware of, but it fixes my issue.
>> 
> 
> Ah, well that's interesting.
> 
> There's a couple of comments:
> 
>   1. you can't do this with just a compile-time test, since the same
>      kernel can also boot native
>   2. nothing in a Xen PV domU environment should be using the tsc
>      directly, so this shouldn't have an effect.  If something is using
>      the tsc we should track it down.
> 
> I wonder, however, if you're getting the same result as Jan's suggestion
> of making sched_clock unstable by making the tsc unstable.

That's what I went for - I had initially just commented out the assignment
of sched_clock_stable to 1, which fixed it, but this felt cleaner.

> In that case, this patch may help:

Will try and report.

Regards,

Jed Smith
Systems Administrator
Linode, LLC
+1 (609) 593-7103 x1209
jed@xxxxxxxxxx


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