Department of Computer Science
University of Maryland
College Park, Maryland 20742
U.S.A.

Accomplishments for First Quarter, 1995

• GNU C based MPL processor completed. Previously MPL was implemented with a preprocessor that generated C code. That implementation had numerous limitations - in particular it could only estimate stack size requirements because it could not predict what compiler temporaries would be generated that used the stack. The new MPL processor is a modification of the Gnu C compiler version 2.5.8. Memory usage requirements are now known exactly, and more accurate control flow analysis can be done.

• New multi-resource allocator/scheduler completed. The previous single-machine scheduler has been replaced with a combined allocator and scheduler that can distribute Maruti applications across many processors sharing a communications bus. A simulated-annealing-based search strategy is used to find a schedule that meets all allocation and scheduling constraints specified by the application. Preemption is now supported on a per-elemental-unit basis: no preemption is done by default, but it can be turned on for certain threads in the application. The allocator/scheduler generates a calendar for each processor and for the communications bus.

• Release Engineering for late spring release. Much of our effort has been directed at preparing for a June release of Maruti to interested researchers. The new tools described above are being integrated and tested with the rest of the system, bug fixes and improvements are being made across the board, and documentation is being updated or filled in.

Accomplishments for Fourth Quarter, 1994

• Maruti/Standalone kernel implemented: An initial version of the Maruti kernel is up and running. Previously Maruti had been implemented via a modified Mach kernel (Maruti/Mach). Maruti/Standalone runs on the bare PC hardware, allowing the full control over resources and timing needed for embedded systems.

• Distributed kernel implemented: An initial version of the kernel support for distributing Maruti applications was completed. Distributed Maruti uses Time Division Multiplexed Access (TDMA) over ethernet for reliable communication. The kernel support includes a specialized ethernet driver, a time-synchronization protocol, and a communications agent to transfer messages over the network.

• Scheduling demo developed: We reimplemented our popular track scheduling demo using a new video driver that uses a standard VGA mode (640x480) rather than the previous Super VGA (1024x768). The new demo also calibrates itself to the system's speed so that uniform timing can be had across different platforms. Using Maruti/Standalone, we are able to put the demo on a floppy and give it away to interested parties. Please contact the Maruti project to obtain a copy of the floppy demo.

• Maruti/Virtual environment: We implemented an initial version of our Unix-based debugging environment. In this environment, Maruti programs run in virtual real-time. The virtual time base can be controlled by the users, allowing for temporal debugging of Maruti applications within the development environment.

• All three runtime environments (Maruti/Mach, Maruti/Standalone, Maruti/Virtual) use the same application object code. The application's code is bound with one of the runtime systems before execution.

• Maruti demos at DSSA Workshop: Maruti technology was demonstrated at the DSSA Workshop at the end of November, 1994. All above items were included in demos given at the meeting.

The Maruti Project

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