RE: [Xen-users] cpufreq problems with hvm

["Tian, Kevin" <kevin.tian@xxxxxxxxx>]

>From: Birger Brunswiek
>Sent: 2008年7月24日 4:58
>
>Hi all,
>I was wondering if cpu frequency scaling in dom0 (using the 
>cpufreq=dom0-kernel 
>boot parameter) may cause problems with HVM domUs? This is on 
>Xen 3.2.1.
>
>PV domUs seem to work just fine. They adjust to the frequency 
>change on the go. 
>The HVM I run using the unmodified_driver drivers (also from 
>the 3.2.1 release) 
>seem to have very slow timers if dom0 lowers the frequency.
>

Current HVM can't cope with freq/tsc change, unless all rdtsc
are trapped which then may bring other side-effects for heavy
overhead. It's better for you to try cpufreq on a platform with
constant TSC, e.g. any Intel processors supporting VT.

Thanks,
Kevin

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