Real-time scheduling theory has developed powerful tools for translating conditions on aggregate system utilization into per-task schedulability guarantees. The main breakthrough has been Liu and Layland's utiliza...
详细信息
Real-time scheduling theory has developed powerful tools for translating conditions on aggregate system utilization into per-task schedulability guarantees. The main breakthrough has been Liu and Layland's utilization bound for schedulability of periodic tasks. In 2001 this bound was generalized by Abdelzaher and Lu to the aperiodic task case. In this paper we further generalize the aperiodic bound to the case of multiprocessors, and present key new insights into schedulability, analysis of aperiodic tasks. We consider a special task model, called the liquid task model, representative of high-performance servers with aperiodic workloads, such as network routers, web servers, proxies, and real-time databases. For this model, we derive the optimal multiprocessor utilization bound, defined on a utilization-like metric we call "synthetic utilization". This bound allows developing constant-time admission control tests that provide utilization-based absolute delay, tees. We show that the real utilization of admitted tasks can be close to unity even when synthetic utilization is kept below the bound. Thus, our results lead to multiprocessor systems which combine constant-time admission control with high utilization while making no periodicity assumptions regarding the task arrival pattern.
In this paper, we consider the mapping of two radar algorithms on a new scalable hardware architecture. The architecture consists of several computational modules that work independently and send data simultaneously i...
详细信息
The preemptive scheduling of systems of periodic tasks on a platform comprised of several identical processors is considered. A scheduling algorithm is proposed for static-priority scheduling of such systems; this alg...
详细信息
ISBN:
(纸本)0769514200
The preemptive scheduling of systems of periodic tasks on a platform comprised of several identical processors is considered. A scheduling algorithm is proposed for static-priority scheduling of such systems; this algorithm is a simple extension of the uniprocessor rate-monotonic scheduling algorithm. It is proven that this algorithm successfully schedules any periodic task system with a worst-case utilization no more than a third the capacity of the multiprocessor platform. It is also shown that no static-priority multiprocessor scheduling algorithm (partitioned or global) can guarantee schedulability for a periodic task set with a utilization higher than one half the capacity of the multiprocessor platform.
This paper shows how the database model of the CHAMP control system architecture must be updated, at times after and at times before different actions in the system. The reason for this is to reach a safe state after ...
详细信息
This paper shows how the database model of the CHAMP control system architecture must be updated, at times after and at times before different actions in the system. The reason for this is to reach a safe state after a fault from which point the control system can make a restart. CHAMP is a control system architecture for manufacturing cells that enhances flexibility.
The paper describes an expert system development toolset called the Production-Based Expert System Toolset (P-BEST) and how it is employed in the development of a modern generic signature analysis engine for computer ...
详细信息
The paper describes an expert system development toolset called the Production-Based Expert System Toolset (P-BEST) and how it is employed in the development of a modern generic signature analysis engine for computer and network misuse detection. For more than a decade, earlier versions of P-BEST have been used in intrusion detection research and in the development of some of the most well known intrusion detection systems, but this is the first time the principles and language of P-BEST are described to a wide audience. We present rule sets for detecting subversion methods against which there are few defenses-specifically, SYN flooding and buffer overruns-and provide performance measurements. Together, these examples and performance measurements indicate that P-BEST based expert systems are well suited for real time misuse detection in contemporary computing environments. In addition, the simplicity of the P-BEST language and its close integration with the C programming language makes it easy to use while still being very powerful and flexible.
作者：
Tomas MollerJohn F. Hughes[a]Brown University
Computer Science Department 115 Waterman Street Providence RI 02912 E-mail: [b]Chalmers University of Technology Department of Computer Engineering 412 96 Gothenburg Sweden E-mail:
We show how to easily create a right-handed orthonormal basis, given a unit vector, in 2−, 3−, and 4-space.
We show how to easily create a right-handed orthonormal basis, given a unit vector, in 2−, 3−, and 4-space.
Snap-shot mechanisms are used to read a globally consistent set of variable values. Methods based on locking are penalized by blocking, which typically leads to difficulties in guaranteeing deadlines of high priority ...
详细信息
Snap-shot mechanisms are used to read a globally consistent set of variable values. Methods based on locking are penalized by blocking, which typically leads to difficulties in guaranteeing deadlines of high priority tasks. A method which combines the predictability of locking-based methods with the low interference (no blocking) of lock-free methods is desirable. In this paper we present one such method, based and the concept of wait-freeness. A wait-free method is a lock-free method which is guaranteed to correctly complete in a bounded number of steps. The price to pay for this predictability in the timing domain is the need for more than one copy of the shared objects. We evaluate our method analytically by formulating and comparing schedulability equations for snapshots in systems using lock-based lock-free and our wait-free method. We also outline ideas to study the effects of using the different snapshot methods in distributed (CAN-based) systems.
In a multiprocessor with a Cache-Only Memory Architecture (COMA) all available memory is used to form large cache memories called attraction memories. These large caches help to satisfy shared memory accesses locally,...
详细信息
In a multiprocessor with a Cache-Only Memory Architecture (COMA) all available memory is used to form large cache memories called attraction memories. These large caches help to satisfy shared memory accesses locally, reducing the need for node-external communication. However since a COMA has no back-up main memory, blocks replaced from one attraction memory must be relocated into another attraction memory. To keep memory overhead low, it is desirable to have most of the memory space filled with unique data. This leaves little space left for replication of cache blocks, resulting in that replacement traffic may become excessive. We have studied two schemes for removing the traditional demand for full inclusion between the lower-level caches and the attraction memory: the loose-inclusion and no-inclusion schemes. They differ in efficiency but also in implementation cost. Detailed simulation results show that the replacement traffic is reduced substantially for both approaches, indicating that breaking inclusion is an efficient way to bound the sensitivity for high memory pressure in COMA machines.
暂无评论