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USENIX Technical Program - Abstract - Windows NT Symposium 99
CPU Reservations and Time Constraints: Implementation Experience on Windows NT
Michael B. Jones, Microsoft Research, Microsoft Corporation; and John Regehr, Department of Computer Science, University of Virginia
Abstract
This paper presents an implementation of scheduling abstractions originally developed for the Rialto real-time operating system within a research version of Windows NT called Rialto/NT. These abstractions, CPU Reservations and Time Constraints, as described in the 1997 SOSP paper [Jones et
al. 97], are intended to allow: (1) activities to obtain minimum
guaranteed execution rates with application-specified reservation
granularities via CPU Reservations, and (2) applications to schedule
tasks by deadlines via Time Constraints, with on-time completion
guaranteed for tasks with accepted constraints.
The Rialto/NT scheduler differs from the original Rialto scheduler
in several key respects. First, it has been extended to schedule
multiprocessors--this is the primary new intellectual contribution
of this work. It has been adapted to operate with operating system
clock services that only provide timing interrupts at regular periodic
intervals measured in milliseconds, rather than being able to schedule
clock interrupts at arbitrary sub-millisecond points of time. It
coexists with the existing Windows NT scheduler, allowing it to
schedule time not scheduled by itself. Finally, it has been
implemented in a particularly non-intrusive manner, using rather than
replacing the existing Windows NT priority-based scheduler.
Results presented will demonstrate that CPU Reservations and Time
Constraints can be effectively implemented on multiprocessors. We
will also describe the implementation techniques chosen and tradeoffs
made as a result of implementing within Windows NT. Finally, we will
present performance results and execution traces.
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