CacheAwareScheduling: What is it and how does Windows benefit?

Old post but some additional info. These values give perfect performance:

[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\kernel]
"CacheAwareScheduling"=dword:00000002 ; testing (0,1,2,4) don't know the default, MS internal use only?
"KernelSEHOPEnabled"=dword:00000000 ; testing (0,1), block exploits that use the Structured Exception Handler overwrite technique
"MaxDynamicTickDuration"=dword:000003e8 ; 1000 uS (Don't use: bcdedit /set disabledynamictick yes)
"MaximumSharedReadyQueueSize"=dword:00000001 ;w12r2 has 1
"SerializeTimerExpiration"=dword:00000002 ;w12r2 has 2

Cheers

St1cky said:

[Defaults] Windows 10 Pro 21H2 - Build: 10.0.19044.1645
CacheAwareScheduling = 7 ( Its not Internal use only, its writeable per Registry. )
MaxDynamicTickDuration = Hex: 54f820d4
MaxDynamicTickDurationSize = Hex: ffffffff
*MinDynamicTickDuration = Decimal: 1000; Hex: 3E8
MaximumSharedReadyQueueSize = Decimal: 260; Hex: 104
SerializeTimerExpiration = 1I tested SerializeTimerExpiration 2, didnt work. Value of 2 sets SerializeTimerExpiration to 0.

So:CacheAwareScheduling has values 0 1 2 3 4 5 6 7 (3 bit flags non documented)
MaxDynamicTickDuration 1000 basicaly disables DynamicTick, since Min value (non registry) is the same
SerializeTimerExpiration 0=def/auto 1=force 2=off (win internals), but 2 falls back to 0 in win10
MaximumSharedReadyQueueSize if I set 256 I get BSOD, 128 works

Is it possible for you to list all these kernel values on your running system (while you are at it)?
Allthough Windows 10 is pretty optimized on this it would be nice to know running values.

Cheers

tweakradje said:

So:CacheAwareScheduling has values 0 1 2 3 4 5 6 7 (3 bit flags non documented)
MaxDynamicTickDuration 1000 basicaly disables DynamicTick, since Min value (non registry) is the same
SerializeTimerExpiration 0=def/auto 1=force 2=off (win internals), but 2 falls back to 0 in win10
MaximumSharedReadyQueueSize if I set 256 I get BSOD, 128 works

Is it possible for you to list all these kernel values on your running system (while you are at it)?
Allthough Windows 10 is pretty optimized on this it would be nice to know running values.

Cheers

Correct, DWORD: MinDynamicTickDuration cannot be changed via the registry, only via debugger.
I didnt tested max value of MaximumSharedReadyQueueSize.

I believe it might be possible to list all values. But the values ​​and names are not the same names as in the registry. Some DWORDs are not associated with a name or it is not readable, more of a guessing game.

Not all settings can be changed via the registry atleast some of them require special combinations or you need the deactived some locks. As I found out, some locks are unlocked by default.

Example: Here, there is a DWORD called KiForceIdleDisabled, but here the prefix already helps us, the next point would be to find out what the registry keyword is, somehow some values ​​are not linked, which could be a problem with IDA. Possibilities would be: "ForceIdleDisabled","IdleForceDisable" etc.

This DWORD is no power setting recognizable by the prefix and I had a different value before that when I tested some other things. Now it's back to 0. Of course, in this example, this DWORD could be linked to power settings.

Idle Strings:

Code:

ActiveIdleLevel
ActiveIdleThreshold
ActiveIdleTimeout
DisableIdleStatesAtBoot
Enlightened Idle
ForceIdleGracePeriod
ForceIdleResetReason
HalProcessorIdle
Idle
IdleAllowScaling
IdleDemoteThreshold
IdleDisable
IdleDurationExpirationTimeout
IdleIntervalCountBucketLimitsInMs
IdleIntervalCountBuckets
IdleMaxDurationInUs
IdleMinDurationInUs
IdlePhaseWatchdog
IdleProcessorsRequireQosManagement
IdlePromoteThreshold
IdleScanInterval
IdleStateCount
IdleStateMax
IdleStateTimeout
IdleTimeCheck
IdleTotalDurationInUs
LatencyToleranceIdleResiliency
PdcIdlePhaseDefaultWatchdogTimeoutSeconds
PoCpuIdledSinceLastCallImprecise
PoFxCompleteIdleCondition
PoFxCompleteIdleCondition
PoFxCompleteIdleState
PoFxCompleteIdleState
PoFxIdleComponent
PoFxIdleComponent
PoFxSetDeviceIdleTimeout
PoFxSetDeviceIdleTimeout
PoGetProcessorIdleAccounting
PoRegisterDeviceForIdleDetection
Power-IdleStatesMax-Enabled
SystemIdle
WorkerFactoryThreadIdleTimeout

Some Code of DynamicTick:

Code:

__int64 __fastcall KiSetupTimeIncrement(unsigned __int64 a1, unsigned int a2)
{
  unsigned int v3; // er9
  unsigned int v4; // eax
  unsigned int v5; // ecx
  unsigned __int64 v6; // rax
  LARGE_INTEGER v7; // rax
  LARGE_INTEGER v8; // rbx
  LARGE_INTEGER v9; // rdi
  unsigned __int64 v10; // rax
  __int64 result; // rax
  char v12; // [rsp+30h] [rbp+8h] BYREF
  char v13; // [rsp+38h] [rbp+10h] BYREF
  LARGE_INTEGER PerformanceFrequency; // [rsp+40h] [rbp+18h] BYREF

  PerformanceFrequency.QuadPart = 0i64;
  v12 = 0;
  v3 = 156250; // Minimum Timer Resolution
  v4 = a2;
  if ( a2 <= 5000 ) // Maximum Timer Resolution ?
    v4 = 5000;
  v5 = KiMinDynamicTickDuration;
  KeMinimumIncrement = v4;
  if ( a1 < 156250 )
    v3 = a1;
  KeMaximumIncrement = v3;
  if ( a2 > KiMinDynamicTickDuration )
  {
    v5 = a2;
    KiMinDynamicTickDuration = a2;
  }
  v6 = KiMaxDynamicTickDuration;
  if ( a1 < KiMaxDynamicTickDuration )
  {
    v6 = a1;
    KiMaxDynamicTickDuration = a1;
  }
  if ( v6 < v5 )
    KiMaxDynamicTickDuration = v5;
  KiTickOffset = v3;
  v13 = 0;
  KiMaximumIncrementReciprocal = RtlpComputeFraction(1u, v3, &v13);
  KeNumberProcessorsGroup0[1] = -v13;
  v7 = KeQueryPerformanceCounter(&PerformanceFrequency);
  v8 = PerformanceFrequency;
  KeTimeAdjustmentFrequency = PerformanceFrequency.QuadPart;
  v9 = v7;
  v10 = RtlGenerateQpcToIncrementConstants(PerformanceFrequency.LowPart, &v12);
  MEMORY[0xFFFFF78000000300] = v8.QuadPart;
  MEMORY[0xFFFFF78000000360] = v10;
  MEMORY[0xFFFFF78000000369] = v12;
  MEMORY[0xFFFFF78000000358] = v10;
  MEMORY[0xFFFFF78000000368] = v12;
  MEMORY[0xFFFFF78000000348] = v9.QuadPart;
  MEMORY[0xFFFFF78000000350] = v9.QuadPart;
  result = 0x989680u / KeMaximumIncrement;
  KiBalanceSetManagerPeriod = 0x989680u / KeMaximumIncrement;
  KiBalanceSetManagerCount = 0x989680u / KeMaximumIncrement;
  return result;
}