Hierarchical schedulers, performance guarantees, and resource management

ManuscriptAn attractive approach to scheduling applications with diverse CPU scheduling requirements is to use different schedulers for different applications. For example: real-time schedulers allow applications to perform computations before deadlines, time-sharing schedulers provide high throughput for compute-bound processes and fast response time for interactive applications, and gang schedulers and cluster coschedulers permit tightly-coupled parallel applications to achieve high performance in the presence of multiprogramming. Furthermore, individual members of these broad classes of algorithms make tradeoffs that may or may not be appropriate for a given situation. In order to take advantage of these diverse algorithms, we permit schedulers to be arranged in a hierarchy - a root scheduler gives CPU time to the schedulers below it in the hierarchy and so on until an application thread is scheduled by a leaf scheduler. This architecture has a number of advantages

Multicore resource management

Current resource management mechanisms and policies are inadequate for future multicore systems. Instead, a hardware/software interface based on the virtual private machine abstraction would allow software policies to explicitly manage microarchitecture resources. VPM policies, implemented primarily in software, translate application and system objectives into VPM resource assignments. Then, VPM mechanisms securely multiplex, arbitrate, or distribute hardware resources to satisfy the VPM assignments.Peer ReviewedPostprint (published version

Hybrid Genetic Algorithms for Scheduling High-Speed Multimedia Systems

It has been observed that most conventional operating systems could not cope with the scheduling of multimedia tasks owing to the large size of these files. For instance, processing of multimedia tasks using the traditional operating systems are fraught with problems such as low quality of service and delay jitters. In order to address these problems, a scheduling algorithm christened hybrid genetic algorithm for multimedia task scheduling (HGAMTS) was developed. It employed heuristic knowledge of the problem domain to model a hybrid genetic algorithm in a multiprocessor environment. The system is made up of the scheduler model and the task model. The scheduler model consist a centralized dynamic scheduling scheme. In this scheme, all tasks arrive at a central processor (scheduler). The model has a minimum of five and maximum of ten processors. Attached to each processor is a dispatch queue

Hierarchical Scheduling for Real-Time Periodic Tasks in Symmetric Multiprocessing

In this paper, we present a new hierarchical scheduling framework for periodic tasks in symmetric multiprocessor (SMP) platforms. Partitioned and global scheduling are the two main approaches used by SMP based systems where global scheduling is recommended for overall performance and partitioned scheduling is recommended for hard real-time performance. Our approach combines both the global and partitioned approaches of traditional SMP-based schedulers to provide hard real-time performance guarantees for critical tasks and improved response times for soft real-time tasks. Implemented as part of VxWorks, the results are confirmed using a real-time benchmark application, where response times were improved for soft real-time tasks while still providing hard real-time performance

Capacity sharing and stealing in serverbased real-time systems

A dynamic scheduler that supports the coexistence of guaranteed and non-guaranteed bandwidth servers is proposed. Overloads are handled by an efficient reclaiming of residual capacities originated by early completions as well as by allowing reserved capacity stealing of non-guaranteed bandwidth servers. The proposed dynamic budget accounting mechanism ensures that at a particular time the currently executing server is using a residual capacity, its own capacity or is stealing some reserved capacity, eliminating the need of additional server states or unbounded queues. The server to which the budget accounting is going to be performed is dynamically determined at the time instant when a capacity is needed. This paper describes and evaluates the proposed scheduling algorithm, showing that it can efficiently reduce the mean tardiness of periodic jobs. The achieved results become even more significant when tasks’ computation times have a large variance

Design and Performance of Configurable Endsystem Scheduling Mechanisms

This paper describes a scheduling abstraction, called group scheduling, that emphasizes fine grain configurability of scheduling system semantics. The group scheduling approach described and evaluated in this paper is an extremely flexible framework within which a wide range of scheduling semantics can be expressed. The paper describes both the OS and middleware based implementations of the framework, and shows through evaluation that they produce the same behavior from a non-trivial set of application computations. Further, the evaluation shows that the framework can easily support application-aware scheduling algorithms to improve performance

The Design, Modeling, and Implementation of Group Scheduling for Isolation of Computations from Adversarial Interference

To isolate computations from denial of service (DoS) attacks and other forms of adversarial interference, it is necessary to constrain the effects of interactions among computations. This paper makes four contributions to research on isolation of computations from adversarial interference: (1) it describes the design and implementation of a kernel level scheduling policy to control the effects of adversarial attacks on computations’ execution; (2) it presents formal models of the system components that are involved in a representative DoS attack scenario; (3) it shows how model checking can be used to analyze that example scenario, under default Linux scheduling semantics and under our scheduling policy design; and (4) it presents empirical studies we have conducted to validate our scheduling policy implementation. Our results show that, with careful design, scheduling and detailed monitoring of computations’ behavior can be combined effectively to mitigate interference of attacks with computations’ execution

Utilization and SLO-Based Control for Dynamic Sizing of Resource Partitions”,

Abstract. This paper deals with a shared server environment where the server is divided into a number of resource partitions and used to host multiple applications at the same time. In a case study where the HP-UX Process Resource Manager is taken as the server partitioning technology, we investigate the technical challenges in performing automated sizing of a resource partition using a feedback control approach, where the CPU entitlement for the partition is dynamically tuned to regulate output metrics such as the CPU utilization or SLO-based application performance metric. We identify the nonlinear and bimodal properties of the models across different operating regions, and discuss their implications for the design of the control loops. To deal with these challenges, we then propose two adaptive controllers for tracking the target utilization and target response time respectively. We evaluate the performance of the closed-loop systems while varying certain operating conditions. We demonstrate that better performance and robustness can be achieved with these controllers compared with other controllers or our prior solution