Re: Xen default install - no cpufreq on dom0 ?

[Andrew Cooper <andrew.cooper3@citrix.com>]

On 23/02/2016 23:44, Luis R. Rodriguez wrote:
> On Tue, Feb 23, 2016 at 10:44:56PM +0000, Andrew Cooper wrote:
>> On 23/02/2016 22:18, 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.
>> You have dislodged the heat sync and the processor is shutting down due
>> to thermal cutout.
> How do I prevent this ?

Open up your computer and shuffle things around.  Alternatively unclog
the fan.  Possibly both.

> The difference in operation between dom0 and
> bare metal is rather extreme. Is this expected ? Is there a clutch
> I can use ?

The only thing software can control is now badly things go wrong.  It is
not the source of the problem.

Baremetal probably has deep C and P states set up properly, but it will
still be under clocking as much as it can in an attempt to avoid
generating as much heat.

~Andrew