No Linux logs when doing `ppc64_cpu --smt=off/8`

[Paul Menzel]

Dear Michal,


Thank you for your reply.

Am 14.02.22 um 10:43 schrieb Michal Suchánek:

> On Mon, Feb 14, 2022 at 07:08:07AM +0100, Paul Menzel wrote:
>> Dear PPC folks,
>>
>>
>> On the POWER8 server IBM S822LC running `ppc64_cpu --smt=off` or `ppc64_cpu
>> --smt=8`, Linux 5.17-rc4 does not log anything. I would have expected a
>> message about the change in number of processing units.
> 
> IIRC it was considered too noisy for systems with many CPUs and the
> message was dropped. You can always check the resulting state with
> ppc64_cpu or examining sysfs.

Yes, simple `nproc` suffice, but I was more thinking about, that the 
Linux log is often used for debugging and the changes of amount of 
processing units might be good to have. `ppc64_cpu --smt=off` or `=8` 
seems to block for quite some time, and each thread/processing unit 
seems to powered down/on sequentially, so it takes quite some time and 
it blocks. So 140 messages would indeed be quite noise. No idea how 
`ppc64_cpu` works, and if it could log a message at the beginning and end.


Kind regards,

Paul