RE: [Xen-devel] Performance difference between Xen versions

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

> From: Konrad Rzeszutek Wilk [mailto:konrad.wilk@xxxxxxxxxx]
> Sent: Tuesday, May 03, 2011 3:36 AM
> 
> > # xenpm get-cpufreq-para 5
> > cpu id               : 5
> > affected_cpus        : 5
> > cpuinfo frequency    : max [2268000] min [1600000] cur [2268000]
> > scaling_driver       : acpi-cpufreq
> > scaling_avail_gov    : userspace performance powersave ondemand
> > current_governor     : ondemand
> >   ondemand specific  :
> >     sampling_rate    : max [10000000] min [10000] cur [20000]
> >     up_threshold     : 80
> > scaling_avail_freq   : *2268000 2267000 2133000 2000000 1867000
> > 1733000 1600000
> > scaling frequency    : max [2268000] min [1600000] cur [2268000]
> > turbo mode           : enabled
> >
> > Does it do it silently? If so, how can I see the true frequency?
> 
> <looks aroud> You are asking me I presume?
> 
> Ummm, no idea. I would actually email the authors of the those patches (CC-ed
> here).

the actual scaling governor runs in the Xen hypervisor. As the default governor 
is
ondemand, which means that Xen tries to scale freq upon workload heuristic 
periodically (e.g. 20ms interval). 

scaling_avail_freq tells you available frequency steppings on current cpu, and
the one marked with "*" is the current freq. But since this call is async with 
the
ongoing ondemand decision, it's probably not the latest one if you just issue
one single call. But if you invoke the call multiple times, and then sample an
average freq, it should be close.

or, you can use "xenpm set-scaling-governor" to choose a different one such as
"userspace" if you want to deploy your own policy from userland.

Thanks
Kevin


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel