Queueing Terms and Littles Law

Queueing Terms
 
T = Measurement Interval
A = Arrivals
Lambda = Arrival Rate = A / T
 
N = Active Customers (Requests)
Q = Queue Length
W = Wait Time
B = Busy Time
C = Completions
S = Service Time = B / C
X = Throughput = C / T
U = Utilization % = S * X = (B / C) * (C / T) = B / T
 
Image: Queueing Terms


Little’s Law: N = X * R
 
Little’s law illustrates the relationship between the number of operations in the system, to the throughput and the response time of a steady state system.
 
N = X * R
 
Where:
N = Number of requests in the system
X = Throughput
R = Time in the System
 
Image: Little’s Law: Variable Definitions, Other Terms & Units

 
Image: Little’s Law Example

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