Horst F. Wedde
Distributed Operating System Support for Scheduling Atomic Real-Time Transactions
EUROMICRO Workshop on Real-Time Systems, Copenhagen, 1990-06
The authors define and discuss novel distributed resource-scheduling algorithms which provide the support for efficient real-time operations on replicated distributed files, realizing them in the manner of distributed atomic real-time transactions. They first define a base algorithm version, called simultaneous enqueuing, and give its relevant properties: starvation-freeness and a minimal message overhead. They then enhance this algorithm by mechanisms which allow for promoting tasks ahead of resource competitors, e.g. because of an earlier deadline. This leads to the hurry-up version of simultaneous enqueuing. A first series of simulation experiments was performed under varying resource contention, and with varying upper bounds for the task laxity, using partial ordering resource scheduling as a benchmark. The results are very favorable for the algorithms which are implemented as part of the kernel services of the real-time version of the distributed operating system DRAGON SLAYER, designer to support is distributed and adaptive replicated file system MELODY.