Windows incorrectly schedules utility QoS threads exclusively to E-cores when running on AC power #117
Description
Windows Build Number
22631
Processor Architecture
AMD64
Memory
64GB
Storage Type, free / capacity
SSD 4TB
Relevant apps installed
WinDbg, LiveKD
Traces collected via Feedback Hub
Isssue description
Windows incorrectly schedules utility QoS threads exclusively to E-cores when running on AC power.
Steps to reproduce
[C:\]
> cd C:\Windows\Temp\
[C:\Windows\Temp]
> $sieve_URI = "https://github.com/kimwalisch/primesieve/releases/download/v11.2/primesieve-11.2-win-x64.zip"
[C:\Windows\Temp]
> Invoke-WebRequest -Uri $sieve_URI -OutFile "sieve.zip"
[C:\Windows\Temp]
> Expand-Archive -Path ".\sieve.zip" -DestinationPath ".\sieve\"
[C:\Windows\Temp]
> schtasks.exe /Create /SC ONLOGON /TN "PrimeSieve" /TR "C:\Windows\Temp\sieve\primesieve.exe 1e12" /NP
SUCCESS: The scheduled task "PrimeSieve" has successfully been created.
[C:\Windows\Temp]
> schtasks.exe /Run /TN "PrimeSieve"
SUCCESS: Attempted to run the scheduled task "PrimeSieve".
[C:\Windows\Temp]
>
Expected Behavior
Windows should schedule utility QoS processes/threads exclusively to E-core only when running on battery power. When running on AC power the default behavior should be kept.
According to the documentation of a company called Microsoft (archive):
QoS level
Utility
Description
Background services
Performance and power
On battery, selects most efficient CPU frequency and schedules to efficient cores.
Release
Windows 11 22H2
Actual Behavior
Windows schedules the process's threads to run only on the E-cores:
Taking a dump using livekd.exe while primesieve.exe is running allows us to verify the thread QoS:
0: kd> dx Debugger.Sessions[0].Processes.Where( p => p.Name == "primesieve.exe" ).First().Threads.Select( t => t.KernelObject.Tcb.BamQosLevel )
Debugger.Sessions[0].Processes.Where( p => p.Name == "primesieve.exe" ).First().Threads.Select( t => t.KernelObject.Tcb.BamQosLevel )
[0x9bac] : 0x6 [Type: unsigned long]
[0x215c] : 0x6 [Type: unsigned long]
[0x9978] : 0x6 [Type: unsigned long]
[0x7e84] : 0x6 [Type: unsigned long]
[0x5fc8] : 0x6 [Type: unsigned long]
[0x5f20] : 0x6 [Type: unsigned long]
[0xf6c] : 0x6 [Type: unsigned long]
[0x5a38] : 0x6 [Type: unsigned long]
[0x5aa8] : 0x6 [Type: unsigned long]
[0xa2b4] : 0x6 [Type: unsigned long]
[0x574c] : 0x6 [Type: unsigned long]
[0x67c4] : 0x6 [Type: unsigned long]
[0x5af4] : 0x6 [Type: unsigned long]
[0xa6d8] : 0x6 [Type: unsigned long]
[0x301c] : 0x6 [Type: unsigned long]
[0xa270] : 0x6 [Type: unsigned long]
[0x42d8] : 0x6 [Type: unsigned long]
[0x378] : 0x6 [Type: unsigned long]
[0xed4] : 0x6 [Type: unsigned long]
[0x84d0] : 0x6 [Type: unsigned long]
[0x2968] : 0x6 [Type: unsigned long]
And as we all know 6 means KHeteroCpuQosUtility.