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kimg

Member

Registered: 2019-09-13

Posts: 3

USB DAC - Low CPU load but excessively high CPU frequency

Hello,

I have an Intel Core i7-8565U based computer so intel_pstate driver and the default powersave CPU frequency scaling governor. When playing audio files through an USB DAC the CPU frequency on all threads goes up from ~1000-1500 Mhz to ~4000 Mhz causing a temperature rise of about 7C. When playing the exact same audio files through my motherboard internal sound card (Realtek ALC892) there is no significant CPU frequency change from baseline or subsequent temperature rise. There is almost no CPU load when checking the top utility under both circumstances.

Main software to play the music files is MPD. Have also tried VLC with the same outcome except a little higher CPU load by the VLC process. Only tested ALSA direct output, bypassing PulseAudio.

Also tried two different USB DACs and tested different USB ports, same problem with both devices no matter what port was used. Both DACs have XMOS XU208 USB interface.

Double checked /proc/asound/card*/pcm*p/sub*/hw_params for both DACs and internal sound card to determine that no re-sampling was taking place.

Have not found any faulty behavior of software and hardware when checking the journal.

This seems like excessive CPU utilization, is there anybody out there that can reproduce this issue and/or have suggestions as to what might be the problem?

rmnet

Member

Registered: 2010-04-16

Posts: 12

Re: USB DAC - Low CPU load but excessively high CPU frequency

Hello

I observe exactly the same thing.

Do you have a recommendation what to do or do you have found a solution for the problem ?

Thanks

LucasBiazi

Member

Registered: 2020-11-11

Posts: 111

Re: USB DAC - Low CPU load but excessively high CPU frequency

I had a similar issue some time ago. Turns out i had not installed a daemon used to prevent the overheating of platforms (which is recommended in the post install suggestions, here: https://wiki.archlinux.org/index.php/Ge … cy_scaling). You can find more about it in the Wiki: https://wiki.archlinux.org/index.php/CP … cy_scaling
Hope it helps.

Last edited by LucasBiazi (2020-12-04 23:04:00)

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Always backup important files when editing it.

kimg

Member

Registered: 2019-09-13

Posts: 3

Re: USB DAC - Low CPU load but excessively high CPU frequency

rmnet, please let me know if running thermald solves the issue. Currently not running Arch on the computer mentioned in the original post so no possibility for me to try. Thanks!

rmnet

Member

Registered: 2010-04-16

Posts: 12

Re: USB DAC - Low CPU load but excessively high CPU frequency

My computer is a Lenovo TkinkPad T490.
Kernel is 5.9.11-arch2-1 #1 SMP PREEMPT Sat, 28 Nov 2020 02:07:22 +0000 x86_64 GNU/Linux

I have now started thermald and with it a new problem ;-)

====
systemctl status thermald.service
● thermald.service - Thermal Daemon Service
     Loaded: loaded (/usr/lib/systemd/system/thermald.service; enabled; vendor preset: disabled)
     Active: inactive (dead) since Sun 2020-12-06 08:57:39 CET; 2h 36min ago
   Main PID: 328 (code=exited, status=0/SUCCESS)

Dec 06 08:57:39 xxxxxxxx systemd[1]: Starting Thermal Daemon Service...
Dec 06 08:57:39 xxxxxxxx systemd[1]: Started Thermal Daemon Service.
Dec 06 08:57:39 xxxxxxxx thermald[328]: 22 CPUID levels; family:model:stepping 0x6:8e:c (6:142:12)
Dec 06 08:57:39 xxxxxxxx thermald[328]: [/sys/devices/platform/thinkpad_acpi/dytc_lapmode] present: Thermald can't run on this platform
Dec 06 08:57:39 xxxxxxxx thermald[328]: Unsupported cpu model or platform
Dec 06 08:57:39 xxxxxxxx systemd[1]: thermald.service: Succeeded.
====

...and the CPU still runs at maximum on sound output via USB.

Seen this on the lenovo forums:
https://forums.lenovo.com/topic/view/27/4028489?page=46

rmnet

Member

Registered: 2010-04-16

Posts: 12

Re: USB DAC - Low CPU load but excessively high CPU frequency

I have now done the following:

1. UEFI BIOS updated from version 1.58 to 1.70.
-> no change

2. intel microcode image (intel-ucode.img) installed and activated (initrd).
-> no change

3. "CPU Power Management" DISABLED in the UEFI BIOS:

====
CPU Power Management

Enables or disables the power saving features that stop the
microprocessor clock automatically when there are no subsystem
activities.
====

Now I can play audio to an external sound card with normal CPU clock.
I hope that disabling "CPU Power Management" will not have unwanted side effects.

Notes:
* Command used for testing: aplay --device plughw:1,0 test.wav
* acpid as well as thermald are disabled.

HTH

kimg

Member

Registered: 2019-09-13

Posts: 3

Re: USB DAC - Low CPU load but excessively high CPU frequency

Thanks rmnet for the trial and error effort. My american megatrends BIOS don't have that specific option. There is a submenu "CPU - Power Management Control" with a multitude of options. Would be interesting to know exactly which option(s) to disable.

Will probably wait to mark this thread as solved until confirmation from another user. Seems a little dicey with all the different BIOSes out there.