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How to Calculate Dehydration

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To calculate dehydration, you use the configured properties and certain run-time values. The following example demonstrates how to calculate a hypothetical dehydration scenario.

To calculate dehydration

  1. Let alpha represent a factor between 0 and 1 that measures memory stress. In practice, alpha has a component for each of the three memory throttling criteria (dehydration properties); in this example we denote them as alpha(virtual), alpha(private) and alpha(physical). Define the following:

    IF ActualPrivateBytes < OptimalUsage  
   alpha(private) = 1  
ELSE IF ActualPrivateBytes > MaximalUsage  
   alpha(private) = 0  
ELSE  
   alpha(private) = (MaximalUsage - ActualPrivateBytes) / (MaximalUsage - OptimalUsage)

    Note

    OptimalUsage and MaximalUsage have default values for each dehydration property. These values can be changed in the BTSNTSvc.exe.config file. For more information, see Dehydration Default Properties.

  2. Define the other alpha components analogously. Define the following:

    alpha = Minimum { alpha(virtual), alpha(private), alpha(physical) }  
where alpha(…) = 1 whenever IsActive=false for that given memory unit

  3. Then define TestThreshold (TestThreshold, MinThreshold, and MaxThreshold are defined in seconds):

    TestThreshold = MinThreshold + (alpha * (MaxThreshold – MinThreshold))

    Note

    MinThreshold default value = 1. MaxThreshold default value = 1800. These values can be changed in the BTSNTSvc.exe.config file. For more information, see Dehydration Default Properties.

  4. Then define TimeBlocked and EstimatedTime:

    • TimeBlocked = actual time we have been waiting for this subscription to be satisfied

    • EstimatedTime = estimated time that this orchestration will remain idle (e.g. remaining timeout on the listen)

    The decision whether to dehydrate is the result of the following Boolean condition (true = dehydrate):

  • Dehydrate = (EstimatedTime > TestThreshold OR TimeBlocked > (2* TestThreshold))

Note

Estimated time is the time remaining until the delay is ended (if delayed for 5 minutes and 2 minutes has passed, TimeBlocked=120 seconds, EstimatedTime=180 seconds).

See Also

Dehydration Default Properties
BTSNTSvc.exe.config File