CPU scaling governors dont work, linux wont obey my command!

Operating Systems & Open Source Linux
1

i have a dell precision m6800 laptop.
i have set sudo cpupower frequency-set -d 2000mhz
but every now and then, the system still allows it to go slower. as low as 600MHZ!


i even get analyzing CPU 0:
  driver: intel_cpufreq
  CPUs which run at the same hardware frequency: 0
  CPUs which need to have their frequency coordinated by software: 0
  maximum transition latency: 20.0 us
  hardware limits: 800 MHz - 3.70 GHz
  available cpufreq governors: ondemand performance schedutil
  current policy: frequency should be within 2.00 GHz and 3.70 GHz.
                  The governor "performance" may decide which speed to use
                  within this range.
  current CPU frequency: Unable to call hardware
  current CPU frequency: 698 MHz (asserted by call to kernel)
  boost state support:
    Supported: yes
    Active: yes

but the slowdowns still happen!! how do make Linux obey my commands here?

2

UPDATE: been doing research. this is apperently a common bug with haswell boards. ive reached out to Dell, they refuse to make a bios update to fix.

somebody at my university told me that AVX causes power spikes in some haswell systems. and that disabling avx might work.
so ive added noxsave to my boot parameters. this disables avx, but not avx2. hopefully its enough. i will run some experiments with this configuration.

i will update this thread with my findings.

3

UPDATE: disabling avx1 didnt fix anything. maybe i also need to find some way to disable avx2?

ill try with clearcpuid=avx,avx2 and post my findings.

4

Hmmm. It seems clearcpuid and noxsave just doesnt work. Avx1 and 2 remain enabled.

5

while i do still suspect avx to be the cause of this issue, linux 6.8 just will not obey the parameter to disable it. unless im doing something wrong.
my current boot parameters are

root=PARTUUID=a327c32c-875f-e54f-9ba0-108bbda50fd8 rw rootfstype=ext4 initrd=\EFI\debian\initrd.img amdgpu.si_support=1 amdgpu.cik_support=1 b43.allhwsupport=1 mitigations=off intel_iommu=on,igfx_off snd_usb_audio.implicit_fb=1 noxsave clearcpuid=avx,avx2

and avx is clearly still enabled because my dmesg has

[  0.132933] x86/fpu: Supporting XSAVE feature 0x004: 'AVX registers'
[  0.142281] raid6: skipped pq benchmark and selected avx2x4
[  0.142281] raid6: using avx2x2 recovery algorithm
[  0.245916] xor: automatically using best checksumming function   avx    
[  5.250089] AVX2 version of gcm_enc/dec engaged.

does anybody here have a working method to disable avx1 and 2?

currently building a new kernel by
CFLAGS=“-fno-tree-vectorize -mno-avx” make -jnproc bindeb-pkg.
hopefully this should result in a kernel that doesnt do avx at all.

update: this diddnt work. the kernel still uses avx. i guess the kernel just doesnt take gcc flags?

now im out of ideas as to how i might disable avx system-wide.

6

apperently some bioses have the option to just disable avx. i wonder if its possible to enable this feature on the precision m6800?