Glossary

averaging window

a sliding window, 100 ms long by default, over which the thread scheduler calculates the CPU percentage usage.

the thread scheduler also keeps track of the usage over longer windows, strictly for reporting purposes. window 2 is typically 10 times the length of the averaging window, and window 3 is typically 100 times the length of the averaging window.

bankruptcy

what happens when critical threads exhaust their partition's critical time budget.

budget

the CPU time, expressed as a fraction of 100%, that a partition is guaranteed to receive when it demands it.

CPU share

another word for budget.

critical budget

a time, in milliseconds, that critical threads are allowed to run even if their partition is out of CPU budget.

critical thread

a thread that's allowed to run, even if its partition is out of CPU budget, provided its partition has a nonzero critical budget.

fair-share schedulers

a class of thread schedulers that consider dynamic processor loads, rather than only fixed thread priorities, in order to guarantee groups of threads some kind of minimum service.

free time

a time period when some partitions aren't demanding their guaranteed CPU percentage.

inheritance

what happens when one thread, usually a message receiver, temporarily adopts the properties of another thread, usually the message sender.

inheritance of partition

what occurs when a message-receiving thread runs in the partition of its message-sender.

microbilling

calculating the small fraction of a clock tick used by threads that block frequently, and counting this time against the threads' partitions.

partition

a division of CPU time, memory, file resources, or kernel resources with some policy of minimum guaranteed usage.

scheduler partition

a named group of threads with a minimum guaranteed CPU budget.

thread scheduler

lets you guarantee minimum percentages of the CPU's throughput (using budgets) to groups of threads, processes, or applications.

throttling

not running threads in one partition, in favor of running threads in another partition, in order to guarantee each their minimum CPU budgets.

underload

The situation when the CPU time that the partitions demand is less than their CPU budgets.