What are the algorithms accuracy limitations?
By accuracy, we mean, how closely the scheduler can guarantee/limit a partition to be consuming only it’s budget on a loaded system. The accuracy limit is whichever of these is greater: • 0.5%, or • tick size (in milliseconds) / windowsize (in milliseconds). For a 100ms window, with a default tick, this is 1%. • When the user changes the averaging windowsize to x milliseconds, the accuracy is undefined for the next x milliseconds. Limitation 1 comes from the accuracy to which the RFF() calculation is carried out. The accuracy of RFF() is calculated to a limited number of bit’s specificially to speed up the scheduling algorithm. Limitation 2 comes from the uncertainty in predicting how long a thread will run before it voluntarily blocks, is preempted by a higher priority thread, or when the next tick interrupt occurs. In other words, this limitation comes from the fact that the AP scheduler is guaranteed control of the system only every tick (but may run more often). In practice, limita
