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Re: KVM wrong CPU speed reported


Fixing that is not back compatible because SOs can be created aligned to
TurboBoost values. Adding global variable switch can be an option.

пт, 28 дек. 2018 г., 7:38 Andrija Panic andrija.panic@xxxxxxxxx:

> I agree Wido, it's just that it's wrong - there should be no implicit CPU
> over-provisioning by default - and yes, later you can do over-provision by
> 2-3 as most of us do...
> just something that hurts my eyes :)
>
> On Fri, 28 Dec 2018 at 11:39, Wido den Hollander <wido@xxxxxxxxx> wrote:
>
> >
> >
> > On 12/28/18 9:23 AM, Andrija Panic wrote:
> > > Hi guys,
> > >
> > >
> >
> https://github.com/apache/cloudstack/commit/29e389eb872ffa816be99aa66ff20bdec56d3187
> > >
> > > this one gets above gets CPU frequency with "effectively
> > > "cat sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_max_freq" which gives
> > the
> > > TurboBoost CPU frequency (in case of Intel CPU) and similar for AMD.
> > >
> > > Problem is that TurboBoost can only boost frequency of a very small
> > number
> > > of CPU cores for a period of time - not by any means all cores.
> > >
> > > CPU frequency is wrongly reported here as i.e. 3.4 GHz instead of 2.6
> GHZ
> > > (example of Intel(R) Xeon(R) CPU E5-2650 v2 @ 2.60GHz)
> > >
> > > We here thus have effective over-provisioning of 30% by default.
> > >
> > > Can we fix this somehow to actually read the base CPU frequency ?
> > > i.e. Xen reports correct CPU frequency (base/nominal one)
> > >
> >
> > Probably fixable by reading a different file on the KVM hypervisor. But
> > I always have the feeling that Ghz are a soft factor. Memory and Storage
> > are hard limits, but CPUs are different.
> >
> > We have a over provision of 2x of 3x on many systems as the CPUs are
> > pretty much idle and the defaults of CS are very conservative.
> >
> > What does a Ghz really tell us? A Ghz from 5 years ago isn't the same as
> > one from today.
> >
> > Wido
> >
> > > Best,
> > >
> >
>
>
> --
>
> Andrija Panić
>