文档介绍：1 Using Hierarchical Using Hierarchical Scheduling to Support Soft Scheduling to Support Soft Real-Time Applications in Real-Time Applications in General-Purpose General-Purpose Operating Systems Operating Systems John Regehr March 20, 2001 2 Outline Outline ? Motivation and Approach ? Guarantees ? HLS Design ? Augmented Reservations ? Conclusions and Demo 3 Overview of Contributions Overview of Contributions ? A general hierarchy of soft real-time schedulers can provide guaranteed scheduling behavior ? The Hierarchical Loadable Scheduler (HLS) architecture …? Can be efficiently implemented in a general- purpose OS ? Increases application performance compared to case where scheduler and apps are mismatched ? Augmented CPU reservations increase predictability when the OS steals CPU time from real-time applications 4 Motivation Motivation ? People use general-purpose OSs (GPOSs) for many kinds of tasks ? . Unix, Windows, MacOS variants ? Compatibility, commodity, convenience ? Applications have diverse scheduling requirements ? Time-sharing ? Soft real-time ? Isolation ? Co-scheduling between processors or machines 5 The Problem The Problem ? One size does not fit all ? Supporting evidence: companies sell scheduler extensions ? Ensim: ServerXchange ? Sun: Solaris Resource Manager ? Aurema: Active Resource Management ? TimeSys: Linux/RT 6 Motivating Data: Unfair CPU Motivating Data: Unfair CPU Allocation Between Users Allocation Between Users ? User 1 gets little CPU time when User 2 creates many threads % 2256 64 16 4 1 N 0 0 00 00 % 100 1 1 1 1 1 N 17 Approach Approach ? Allow a hierarchy of CPU schedulers to control processor allocation ? Thesis Statement: ? It is useful and feasible to extend a GPOS with a general, heterogeneous scheduling hierarchy. ? A heterogeneous hierarchy employs different schedulers ? A general hierarchy does not impose a fixed scheduling model 8 Exam