Re: Xen default install - no cpufreq on dom0 ?

[Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>]

On Tue, Feb 23, 2016 at 11:18:09PM +0100, Luis R. Rodriguez wrote:
> 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.

OK, serial console output pls with full debug :-)
> 
> > > 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.

No idea as I never had this issue on my systems. And I've a ton of different
hardware (desktops, laptops, servers, etc) running with Xen.

> 
>   Luis