Re: [Xen-devel] Xen default install - no cpufreq on dom0 ?

["Luis R. Rodriguez" <mcgrof@xxxxxxxxxx>]

On Tue, Feb 23, 2016 at 05:00:12PM -0500, Konrad Rzeszutek Wilk wrote:
> On Tue, Feb 23, 2016 at 12:48:18PM -0800, Luis R. Rodriguez wrote:
> > For a while now I've been installing Xen from source on my Debian box,
> > with a default configuration always. This is party why I've run into
> > compile issues before it seems, but I've also just picked up on
> > another possible issue. My system on dom0 overheats and shuts itself
> > off. For a while I didn't think this was Xen related and perhaps
> > related to the fact that I built this system myself. However, after
> > running Debian without Xen (rm -rf /boot/xen*; update-grub; reboot;
> > systemd-detect-virt yield none) it would seem this does not happen.
> > What's a bit concerning though is even if I run offlineimap in
> > singlethreaded mode (offlineimap -1) the machine overheats and shuts
> > itself off, so I don't necessarily need to be doing a lot of work. I
> > tried compiling the kernel without Xen while running offlineimap as
> > well with make -j 8 and it doesn't overheat, meanwhile on Xen dom0
> > just using offlineimap -1 seems to trigger a shutoff rather quickly.
> 
> What exactly triggers the shutoff.

Clearly, overheating. I'm not yet sure if its just BIOS/kernel/hypervisor
induced forced shutdown. Will try again, but this is rather intrusive as
its on my personal home system.

> > The kernel has:
> > 
> > CONFIG_CPU_FREQ_GOV_PERFORMANCE=y
> > 
> > I tried on /etc/default/grub
> > 
> > GRUB_CMDLINE_LINUX_XEN_REPLACE="cpufreq=dom0-kernel"
> > 
> > But that didn't help. This is running 4.5.0-rc2 and the latest Xen I
> > was able to build (I try xen staging tree always).
> 
> Right.  We are actually going to remove that option as it makes no sense
> for Linux (dom0) to control the cpu frequency.
> 
> Irrespective of that - there are simply no drivers in dom0 that would
> do the cpufreq for you (unless you recompile the kernel and edit in
> arch/x86/xen/enlighten.c the calls to disable cpuidle and cpufreq code).

How can I (and Xen by default) not overheat a system then ?
What's the short term and long term plan? I was a bit surprised
a simple single threaded offlineimap would force a shutoff on
Xen. I figured I must be seriously misconfiguring something
but this is just running with defaults.

  Luis

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