RE: [Xen-devel] [PATCH] replace rdtsc emulation-vs-native xen boot option with per-domain (hypervisor part)

[Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>]

> On 09/28/09 15:43, Dan Magenheimer wrote:
> > PV ones too.  An app doesn't have any idea (and doesn't
> > and shouldn't care) if it is running on a PV or HVM domain.  
> 
> Well, it shouldn't be enabled by default.  That slows down all rdtsc
> operations for the benefit of very niche applications.  The Xen
> clocksource assumes that rdtsc is fast, unemulated and in need of
> correction.
> 
> If someone really needs an artificial tsc, then they can enable the
> option for themselves.

While I understand and sympathize (and the idealistic side of me even
agrees with) your position, let me argue your point "they can enable
the option for themselves" by mangling a famous movie quote:

      "In a cloud, no-one can hear rdtsc scream"

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