14.0-RELEASE-p6 High acpi_task_* CPU utilization

From: Steve Bernacki <steve_at_copacetic.net>
Date: Thu, 28 Mar 2024 15:20:16 UTC
Hello,

I've just installed FreeBSD 14.0-RELEASE-p6 (GENERIC) on a AWOW Mini PC 
[1]. Completely idle, top(1) reports unusually high system CPU usage:

   CPU:  0.0% user,  0.0% nice, 27.7% system,  0.0% interrupt, 72.3% idle

Running top -SH reveals that the CPU time is being consumed by kernel 
acpi_tasks:

   PID USERNAME    PRI NICE   SIZE    RES STATE    C   TIME    WCPU COMMAND
    11 root        187 ki31     0B    64K CPU0     0  29:22  97.15% 
idle{idle: cpu0}
    11 root        187 ki31     0B    64K RUN      2  22:05  74.21% 
idle{idle: cpu2}
    11 root        187 ki31     0B    64K CPU3     3  22:11  73.37% 
idle{idle: cpu3}
    11 root        187 ki31     0B    64K RUN      1  21:59  70.21% 
idle{idle: cpu1}
     0 root          8    -     0B  1456K -        0   8:08  29.74% 
kernel{acpi_task_1}
     0 root          8    -     0B  1456K CPU3     3   8:30  28.67% 
kernel{acpi_task_2}
     0 root          8    -     0B  1456K CPU1     1   8:31  26.09% 
kernel{acpi_task_0}

The BIOS configurables for this system are pretty sparse; I'm not able 
to see or adjust any ACPI settings. Relevant (I hope) snippets from 
dmesg below:

======
CPU: Intel(R) Celeron(R) CPU N3450 @ 1.10GHz (1094.62-MHz K8-class CPU)
   Origin="GenuineIntel"  Id=0x506c9  Family=0x6  Model=0x5c Stepping=9
Features=0xbfebfbff<FPU,VME,DE,PSE,TSC,MSR,PAE,MCE,CX8,APIC,SEP,MTRR,PGE,MCA,CMOV,PAT,PSE36,CLFLUSH,DTS,ACPI,MMX,FXSR,SSE,SSE2,SS,HTT,TM,PBE>
Features2=0x4ff8ebb7<SSE3,PCLMULQDQ,DTES64,DS_CPL,VMX,EST,TM2,SSSE3,SDBG,CX16,xTPR,PDCM,SSE4.1,SSE4.2,x2APIC,MOVBE,POPCNT,TSCDLT,AESNI,XSAVE,OSXSAVE,RDRAND>
   AMD Features=0x2c100800<SYSCALL,NX,Page1GB,RDTSCP,LM>
   AMD Features2=0x101<LAHF,Prefetch>
   Structured Extended 
Features=0x2294e283<FSGSBASE,TSCADJ,SMEP,ERMS,NFPUSG,MPX,PQE,RDSEED,SMAP,CLFLUSHOPT,PROCTRACE,SHA>
   XSAVE Features=0xf<XSAVEOPT,XSAVEC,XINUSE,XSAVES>
   VT-x: PAT,HLT,MTF,PAUSE,EPT,UG,VPID,VID,PostIntr
   TSC: P-state invariant, performance statistics
real memory  = 6442450944 (6144 MB)
avail memory = 5978120192 (5701 MB)
Event timer "LAPIC" quality 600
ACPI APIC Table: <INTEL  EDK2    >
[snip]
smbios0: <System Management BIOS> at iomem 0xf05e0-0xf05fe
smbios0: Version: 3.0, BCD Revision: 3.0
aesni0: <AES-CBC,AES-CCM,AES-GCM,AES-ICM,AES-XTS,SHA1,SHA256>
acpi0: <ALASKA A M I >
acpi0: Power Button (fixed)
unknown: I/O range not supported
ACPI Error: No handler for Region [ECF2] (0xfffff800038c2680) 
[EmbeddedControl] (20221020/evregion-292)
ACPI Error: Region EmbeddedControl (ID=3) has no handler 
(20221020/exfldio-428)
ACPI Error: Aborting method \134_SB.PCI0.SBRG.H_EC.BAT0._STA due to 
previous error (AE_NOT_EXIST) (20221020/psparse-689)
cpu0: <ACPI CPU> on acpi0
attimer0: <AT timer> port 0x40-0x43,0x50-0x53 irq 0 on acpi0
[snip]
Timecounter "ACPI-fast" frequency 3579545 Hz quality 900
acpi_timer0: <32-bit timer at 3.579545MHz> port 0x408-0x40b on acpi0
acpi_ec0: <Embedded Controller: GPE 0x2c> port 0x62,0x66 on acpi0
pcib0: <ACPI Host-PCI bridge> port 0xcf8-0xcff on acpi0
pci0: <ACPI PCI bus> on pcib0
======

Relevant kenv output:

======
acpi.oem="ALASKA"
acpi.revision="2"
acpi.rsdp="0x000f05b0"
acpi.rsdt="0x793a5030"
acpi.xsdt="0x00000000793a50c0"
acpi.xsdt_length="36"
acpi_dsdt_load="NO"
acpi_dsdt_name="/boot/acpi_dsdt.aml"
acpi_dsdt_type="acpi_dsdt"
acpi_video_load="NO"
hint.acpi_throttle.0.disabled="1"
smbios.bios.reldate="09/30/2022"
smbios.bios.revision="4.6"
smbios.bios.vendor="American Megatrends Inc."
smbios.bios.version="4.06"
smbios.chassis.type="Mini PC"
smbios.memory.enabled="6291456"
smbios.planar.maker="AWOW Technology Co., Ltd."
smbios.planar.product="PC BOX"
smbios.system.product="AK34"
======

The few search results for similar issues I've found suggest trying to 
disable ACPI altogether, which just results in the kernel immediately 
panicking when booting.

Any suggestions on how I can troubleshoot this further?

Thank you
Steve

[1] https://www.amazon.com/gp/product/B0B4RMLCH7/?th=1