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xen-users
Re: [Xen-users] cpufreq problems with hvm
Tian, Kevin wrote:
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.
I see ... it's just when the last time I looked for Intel CPUs it way quite
difficult to get those with VT in the consumer segment. That's quite different
with AMD.
Does anyone know if the modules (?) which are responsible to get the freq
scaling right in PVs can be used/ported to an HVM? Similar to the unmodified
drivers to use a paravirtualised disk and netif.
Birger
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