AMD Ryzen 7 PRO 7735U: 8 instead of 16 CPUs?

AMD Ryzen 7 PRO 7735U: 8 instead of 16 CPUs?

[Dirk Gouders]

I got new hardware and after setting up everything, I was wondering why
I don't see the expected 16 CPUs in top(1) or /proc/cpuinfo...

From the AMD website [1] I read:
------------------------------------------------------------------------
Name                    AMD Ryzen™ 7 PRO 7735U
...
Architecture            Zen 3+
# of CPU Cores          8
...
# of Threads            16
------------------------------------------------------------------------

But lscpu(1) shows me:
------------------------------------------------------------------------
Architecture:             x86_64
  CPU op-mode(s):         32-bit, 64-bit
  Address sizes:          48 bits physical, 48 bits virtual
  Byte Order:             Little Endian
CPU(s):                   8
  On-line CPU(s) list:    0-7
Vendor ID:                AuthenticAMD
  Model name:             AMD Ryzen 7 Pro 7735U with Radeon Graphics
    CPU family:           25
    Model:                68
    Thread(s) per core:   2
    Core(s) per socket:   4
    Socket(s):            1

------------------------------------------------------------------------

Then, I booted a BSD livesystem (NomadBSD), looked at dmesg(1):
------------------------------------------------------------------------
# dmesg | grep SMP
FreeBSD/SMP: Multiprocessor System Detected: 16 CPUs
FreeBSD/SMP: 1 package(s) x 8 core(s) x 2 hardware threads
------------------------------------------------------------------------

And I installed it's lscpu(1) and that reports:
------------------------------------------------------------------------
Architecture:            amd64
Byte Order:              Little Endian
Total CPU(s):            16
Thread(s) per core:      2
Core(s) per socket:      8
Socket(s):               1
Vendor:                  AuthenticAMD
CPU family:              25
Model:                   68
Model name:              AMD Ryzen 7 Pro 7735U with Radeon Graphics     
------------------------------------------------------------------------

Do I misunderstand something from the above?

Best regards,

Dirk

[1] https://www.amd.com/en/products/processors/laptop/ryzen-pro/7000-series/amd-ryzen-7-pro-7735u.html

Re: AMD Ryzen 7 PRO 7735U: 8 instead of 16 CPUs?

[Borislav Petkov]

On Wed, Apr 09, 2025 at 12:49:14PM +0200, Dirk Gouders wrote:
> I got new hardware and after setting up everything, I was wondering why
> I don't see the expected 16 CPUs in top(1) or /proc/cpuinfo...

Send full dmesg pls.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette

Re: AMD Ryzen 7 PRO 7735U: 8 instead of 16 CPUs?

[Dirk Gouders]

Borislav Petkov <bp@alien8.de> writes:

> On Wed, Apr 09, 2025 at 12:49:14PM +0200, Dirk Gouders wrote:
>> I got new hardware and after setting up everything, I was wondering why
>> I don't see the expected 16 CPUs in top(1) or /proc/cpuinfo...
>
> Send full dmesg pls.

Oh well, thanks for the hint: CONFIG_NR_CPUS=8

And if I had analyzed that better, I would have noticed myself:

[    0.059658] CPU topo: CPU limit of 8 reached. Ignoring further CPUs
...
[    0.059709] CPU topo: Rejected CPUs 8


OK, next recipients are the amdgpu folks with a trace that has a higher
chance the problem isn't me...

Best regards,

Dirk

Re: AMD Ryzen 7 PRO 7735U: 8 instead of 16 CPUs?

[Borislav Petkov]

On Wed, Apr 09, 2025 at 02:11:49PM +0200, Dirk Gouders wrote:
> Oh well, thanks for the hint: CONFIG_NR_CPUS=8

Yeah, that option has been known to be very strict, stingy and not giving even
a single CPU more than specified!

:-P :-P

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette