Multi-threaded programming is difficult and error prone. It is easy to make a mistake in synchronization that produces a data race, yet it can be extremely hard to locate this mistake during debugging. This paper describes a new tool, called Eraser, for dynamically detecting data races in lock-based multi-threaded programs. Eraser uses binary rewriting techniques to monitor every shared memory reference and verify that consistent locking behavior is observed. We present several case studies, including undergraduate coursework and a multi-threaded Web search engine, that demonstrate the effectiveness of this approach. 1

This paper presents a novel interprocedural, flow-sensitive, and context-sensitive pointer analysis algorithm for multithreaded programs that may concurrently update shared pointers. For each pointer and each program point, the algorithm computes a conservative approximation of the memory locations to which that pointer may point. The algorithm correctly handles a full range of constructs in multithreaded programs, including recursive functions, function pointers, structures, arrays, nested structures and arrays, pointer arithmetic, casts between pointer variables of different types, heap and stack allocated memory, shared global variables, and thread-private global variables. We have implemented the algorithm in the SUIF compiler system and used the implementation to analyze a sizable set of multithreaded programs written in the Cilk multithreaded programming language. Our experimental results show that the analysis has good precision and converges quickly for our set of Cilk programs.

UNIX Internet servers with an event-driven architecture often perform poorly under real workloads, even if they perform well under laboratory benchmarking conditions. We investigated the poor performance of event-driven servers. We found that the delays typical in wide-area networks cause busy servers to manage a large number of simultaneous connections. We also observed that the select system call implementation in most UNIX kernels scales poorly with the number of connections being managed by a process. The UNIX algorithm for allocating file descriptors also scales poorly. These algorithmic problems lead directly to the poor performance of event-driven servers. We implemented scalable versions of the select system call and the descriptor allocation algorithm. This led to an improvement of up to 58% in Web proxy and Web server throughput, and dramatically improved the scalability of the system.

Cooperative task management can provide program architects with ease of reasoning about concurrency issues. This property is often espoused by those who recommend "event-driven" programming over "multithreaded " programming. Those terms conflate several issues. In this paper, we clarify the issues, and show how one can get the best of both worlds: reason more simply about concurrency in the way "event-driven" advocates recommend, while preserving the readability and maintainability of code associated with "multithreaded" programming. We identify the source of confusion about the two programming styles as a conflation of two concepts: task management and stack management. Those two concerns define a two-axis space in which "multithreaded" and "event-driven" programming are diagonally opposite; there is a third "sweet spot" in the space that combines the advantages of both programming styles. We point out pitfalls in both alternative forms of stack management, manual and automatic, and we supply techniques that mitigate the danger in the automatic case. Finally, we exhibit adaptors that enable automatic stack management code and manual stack management code to interoperate in the same code base.

ions To provide remote execution of both parallel and sequential jobs, GLUnix extends some existing UNIX abstractions and introduces new abstractions, borrowing heavily from MPP environments such as that of the CM-5. The new abstractions include network programs and globally unique network program identifiers (NPIDs) for GLUnix jobs and virtual node numbers (VNNs) to name the nodes running a network program. The existing abstractions of signal delivery to remote applications and I/O redirection were extended to support parallel and remote jobs. GLUnix provides both programming and command-line interfaces to access these abstractions. Network Programs A network program is an executing parallel or sequential job that is controlled by GLUnix. Network programs can be located anywhere in the cluster and are identified using a 32-bit, cluster-unique network program identifier (NPID) which is assigned and tracked by GLUnix. Using a cluster-wide, location-independent identifier provides th...

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Permission is hereby granted to make and distribute verbatim copies of this document without royalty or fee. Permission is granted to quote excerpts from this documented provided the original source is properly cited. ii When separately written programs are composed so that they may cooperate, they may instead destructively interfere in unanticipated ways. These hazards limit the scale and functionality of the software systems we can successfully compose. This dissertation presents a framework for enabling those interactions between components needed for the cooperation we intend, while minimizing the hazards of destructive interference. Great progress on the composition problem has been made within the object paradigm, chiefly in the context of sequential, single-machine programming among benign components. We show how to extend this success to support robust composition of concurrent and potentially malicious components distributed over potentially malicious machines. We present E, a distributed, persistent, secure programming language, and CapDesk, a virus-safe desktop built in E, as embodiments of the techniques we explain.

Widely-used operating systems provide inadequate support for large-scale Internet server applications. Their algorithms and interfaces fail to efficiently support either event-driven or multi-threaded servers. They provide poor control over the scheduling and management of machine resources, making it difficult to provide robust and controlled service. We propose new UNIX interfaces to improve scalability, and to provide fine-grained scheduling and resource management. 1 Introduction The performance of Internet server applications on a general purpose operating system is often dismayingly lower than what one would expect from the underlying hardware. Internet servers also suffer from other undesirable properties such as poor scalability, unfair resource allocation, susceptibility to livelock under excess load, instability under denial of service attacks, and inability to prioritize handling of requests. The cause of these problems is a fundamental mismatch between the original design ...

The use of threads is becoming commonplace in both sequential and parallel programs. This paper describes our design and initial experience with non-trace based performance instrumentation techniques for threaded programs. Our goal is to provide detailed performance data while maintaining control of instrumentation costs. We have extended Paradyn's dynamic instrumentation (which can instrument programs without recompiling or relinking) to handle threaded programs. Controlling instrumentation costs means efficient instrumentation code and avoiding locks in the instrumentation. Our design is based on low contention data structures. To associate performance data with individual threads, we have all threads share the same instrumentation code and assign each thread with its own private copy of performance counters or timers. The asynchrony in a threaded program poses a major challenge to dynamic instrumentation. To implement time-based metrics on a per-thread basis, we need to instrument t...

We develop new methods to statically bound the resources needed for the execution of systems of concurrent, interactive threads.