Re: [PATCH] turbostat: Running on virtual machine is not supported

Re: [PATCH] turbostat: Running on virtual machine is not supported

[Prarit Bhargava]

On 07/26/2017 11:09 PM, Len Brown wrote:
> Henrique,
> 
> I like your suggestion, thanks!
> 
> BTW. let's discuss (and patch) turbostat on linux-pm, rather than on lkml.
> 
> thanks,
> -Len
> 
> 
> On Tue, Jul 25, 2017 at 11:59 AM, Henrique de Moraes Holschuh
> <hmh@hmh.eng.br> wrote:
>> On Tue, 25 Jul 2017, Prarit Bhargava wrote:
>>> A common way of determining if the system is a virtual machine is to
>>> search /proc/cpuinfo flags entry for "hypervisor".  turbostat must output
>>> a proper error message when found.
>>
>> Maybe you could output that message only if it fails to both use
>> /dev/msr and perf *and* it is under a virtual machine?  That would have
>> better forward compatibility, maybe someday /dev/msr or perf will work
>> inside a VM for what turbostat needs...

To answer Len's previous question: I was wrong in my description.  perf does
work (mostly) under virt.  So this would only be for the msr code.  I'll post a
v2 to linux-pm, and take Henrique's suggestion to only trigger on an msr read
failure.

P.

>>
>> --
>>   Henrique Holschuh
> 
> 
> 

Re: [PATCH] turbostat: Running on virtual machine is not supported

[Len Brown]

>  perf does work (mostly) under virt.

Let's hold off on this patch for a bit till the port to perf is ready,
since this logic is going to change slightly.

I think something like this:

1. make the debug info (the stuff hidden with --quiet) optional
    don't bail out if it fails.  (but continue to bail out of anything
    that is needed to provide a column fails)

2. attempt the faster of /dev/msr or perf first, and try the 2nd
    only when the 1st doesn't work.

   (currently /dev/msr is faster, but I'm not done w/ the perf work)

3. When neither /dev/msr or perf work, then check for virt
    to see if it may be the cause.

   Print the error message about permissions for perf and /dev/msr and
virt, as appropriate.

thanks,
Len Brown, Intel Open Source Technology Center