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

[Ian Pratt <Ian.Pratt@xxxxxxxxxxxxx>]

> > 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"

If we had some actual bug reports detailing failures of real-world applications 
then the decision would be easy.

I realise it could be hard to pin strange application behaviour down to TSC 
issues, but I can't readily spot any bugs on the XenServer or xen.org bug 
trackers that might even be candidates. 

Ian


 

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