How does AP guarantee a partitions minimum cpu budget?
The adaptive partitioning scheduler guarantees a minimum CPU budget by ensuring that other partitions do not overrun their budget. This determination is made every clock tick. The AP scheduler is invoked by the clock interrupt handler. That means it runs a minimum of every clock period (typically every millisecond). On each clock tick: • On a uni-processor, it examines the partition of the currently running thread to see if it should keep running. The AP scheduler will decide if a thread should stop running if its partition has less available time (budget-cycles minus used-cycles during this averaging window) than what is necessary to pay for the duration of the next clock period. If the currently running partition fails this test then the AP portion of the clock handler sets a “must examine all partitions” flag
• On an SMP processor, the AP scheduler’s portion of the clock interrupt handler always sets the “must examine all partitions flag”. On exit from the Neutrino clock interr
