On the Shadow Cpu Approximation for Modelling Priority Scheduling in Computer Systems (Classic Reprint)

Excerpt from On the Shadow Cpu Approximation for Modelling Priority Scheduling in Computer Systems We shall use a model proposed by [sevc, 77] that contains very little of the complexity of an actual system but still reflects the intrinsic difficulty of analytically approaching priority scheduling. flue queuing network is a closed cyclic uetggtg_of two servers: a cpu and an i/o server. There are just two cystomer classes, with class 1 having pre-emptive priority over class -the cpu, while all scheduling is fcfs at the i/o. That L(jiept-rlazl processor will be devoted to class 1 whenever a class 1_job; is, availahle for service. Within each class jobs are served irpyfcejsiggdetfl'og-ixhe average service times at the i/o are the same (x3) ffxyboghggiasse§ hut the average cpu service times (bemeen i/o -t-=for the two classes (xi for class i, i Jobs always teturn to the cpu after being served at the i/o. We assume, for simplicity, that the service time distribution of the i/o is exponential (of rate u3 X51) and the cpu service for class 1 is exponential (rate 1 Xfl). For class 2 the same holds, when the cpu service time distribution is conditional to the event of absence of class 1 jobs from the cpu. About the Publisher Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works.