Application domains such as multimedia, databases, and parallel computing, require operating system services with high performance and high functionality. Existing operating systems provide fixed interfaces and implementations to system services and resources. This makes them inappropriate for applications whose resource demands and usage patterns are poorly matched by the services provided. The SPIN operating system enables system services to be defined in an application-specific fashion, through an extensible microkernel. It offers applications fine-grained control over a machine's logical and physical resources through run-time adaptation of the system to application requirements. 1

Recent shared-memory parallel computer systems offer the exciting possibility of customizing memory coherence protocols to fit an application's semantics and sharing patterns. Custom protocols have been used to achieve message-passing performance---while retaining the convenient programming model of a global address space---and to implement high-level language constructs. Unfortunately, coherence protocols written in a conventional language such as C are difficult to write, debug, understand, or modify. This paper describes Teapot, a small, domain-specific language for writing coherence protocols. Teapot uses continuations to help reduce the complexity of writing protocols. Simple static analysis in the Teapot compiler eliminates much of the overhead of continuations and results in protocols that run nearly as fast as hand-written C code. A Teapot specification can be compiled both to an executable coherence protocol and to input for a model checking system, which permits the specifica...

We describe computation migration, a new technique that is based on compile-time program transformations, for accessing remote data in a distributed-memory parallel system. In contrast with RPC-style access, where the access is performed remotely, and with data migration, where the data is moved so that it is local, computation migration moves part of the current thread to the processor where the data resides. The access is performed at the remote processor, and the migrated thread portion continues to run on that same processor; this makes subsequent accesses in the thread portion local. We describe an implementation of computation migration that consists of two parts: an implementation that migrates single activation frames, and a high-level language annotation that allows a programmer to express when migration is desired. We performed experiments using two applications; these experiments demonstrate that computation migration is a valuable alternative to RPC and data migration.

Recent advances in I/O bus structures (e.g., PCI), highspeed networks, and fast, cheap disks have significantly expanded the I/O capacity of desktop-class systems. This paper describes a messaging system designed to deliver the potential of these advances for network storage systems including cluster file systems and network memory. We describe gms net, an RPClike kernel-kernel messaging system based on Trapeze, a new firmware program for Myrinet network interfaces. We show how the communication features of Trapeze and gms net are used by the Global Memory Service (GMS), a kernel-based network memory system. The paper focuses on support for zero-copy page migration in GMS/Trapeze using two RPC variants important for peer-peer distributed services: (1) delegated RPC in which a request is delegated to a third party, and (2) nonblocking RPC in which replies are processed from the Trapeze receive interrupt handler. We present measurements of sequential file access from network memory in t...

Traditional operating systems use a fixed LRU-like page replacement policy and centralized frame pool that cannot properly serve all types of memory access patterns of various applications. As a result, many memory-intensive applications, such as databases, multimedia applications and scientific simulators, induce excessive page faults and page replacement when running on top of existing operating systems. This paper presents a High Performance External virtual memory Caching mechanism (HiPEC) to provide applications with their own specific page replacement management. The user specific policy, programmed in the HiPEC command set, is stored in user address space. When a page fault occurs, the kernel fetches and interprets the corresponding policy commands to perform the user-specific page replacement management. Experimental results show that HiPEC induces little overhead and can significantly improve performance for memory-intensive applications. 1 Introduction Though technological a...

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We have defined and implemented a kernel API that makes every exported operation fully interruptible and restartable, thereby appearing atomic to the user. To achieve interruptibility, all possible kernel states in which a thread may become blocked for a "long" time are represented as kernel system calls, without requiring the kernel to retain any unexposable internal state. Since all kernel operations appear atomic, services such as transparent checkpointing and process migration that need access to the complete and consistent state of a process can be implemented by ordinary user-mode processes. Atomic operations also enable applications to provide reliability in a more straightforward manner. This API also allows us to explore novel kernel implementation techniques and to evaluate existing techniques. The Fluke kernel's single source implements either the "process" or the "interrupt" execution model on both uniprocessors and multiprocessors, depending on a configuration option affec...

This paper presents a new asynchronous programming library (libasync-smp) that allows event-driven applications to take advantage of multiprocessors by running code for event handlers in parallel. To control the concurrency between events, the programmer can specify a color for each event: events with the same color (the default case) are handled serially; events with different colors can be handled in parallel. The programmer can incrementally expose parallelism in existing event-driven applications by assigning different colors to computationally-intensive events that do not share mutable state. An

EMERALDS (Extensible Microkernel for Embedded, ReAL-time, Distributed Systems) is a real-time microkernel designed for small-memory embedded applications. These applications must run on slow (15--25MHz) processors with just 32--128 kbytes of memory, either to keep production costs down in mass-produced systems or to keep weight and power consumption low. To be feasible for such applications, the OS must not only be small in size (less than 20 kbytes) but also have low-overhead kernel services. Unlike commercial embedded OSs which rely on carefully-optimized code to achieve efficiency, EMERALDS takes the approach of redesigning the basic OS services of task scheduling, synchronization, communication, and system call mechanism by using characteristics found in small-memory embedded systems such as small code size and a priori knowledge of task execution & communication patterns. With these new schemes, the overheads of various OS services are reduced 20--40% without compromising any OS functionality.

In this paper we describe a new, low-overhead technique for manipulating processor interrupt state in an operating system kernel. Both uniprocessor and multiprocessor operating systems protect against uniprocessor deadlock and data corruption by selectively enabling and disabling interrupts during critical sections. This happens frequently during latency-critical activities such as IPC, scheduling, and memory management. Unfortunately, the cycle cost of modifying the interrupt mask has increased by an order of magnitude in recent processor architectures. In this paper we describe optimistic interrupt protection, a technique which substantially reduces the cost of interrupt masking by optimizing mask manipulation for the common case of no interrupts. We present results for the Mach 3.0 microkernel operating system, although the technique is applicable to other kernel architectures, both micro and monolithic, that rely on interrupts to manage devices. 1 Introduction This paper describes...