摘要:
The systems and methods described herein may be used to implement a shared dynamic-sized data structure using hardware transactional memory to simplify and/or improve memory management of the data structure. An application (or thread thereof) may indicate (or register) the intended use of an element of the data structure and may initialize the value of the data structure element. Thereafter, another thread or application may use hardware transactions to access the data structure element while confirming that the data structure element is still part of the dynamic data structure and/or that memory allocated to the data structure element has not been freed. Various indicators may be used determine whether memory allocated to the element element can be freed.
摘要:
The systems and methods described herein may be used to implement a shared dynamic-sized data structure using hardware transactional memory to simplify and/or improve memory management of the data structure. An application (or thread thereof) may indicate (or register) the intended use of an element of the data structure and may initialize the value of the data structure element. Thereafter, another thread or application may use hardware transactions to access the data structure element while confirming that the data structure element is still part of the dynamic data structure and/or that memory allocated to the data structure element has not been freed. Various indicators may be used determine whether memory allocated to the element can be freed.
摘要:
We teach a powerful approach that greatly simplifies the design of non-blocking mechanisms and data structures, in part by, largely separate the issues of correctness and progress. At a high level, our methodology includes designing an “obstruction-free” implementation of the desired mechanism or data structure, which may then be combined with a contention management mechanism whose role is to facilitate the conditions under which progress of the obstruction-free implementation is assured. In general, the contention management mechanism is separable semantically from an obstruction-free concurrent shared/sharable object implementation to which it is/may be applied. In some cases, the contention management mechanism may actually be coded separately from the obstruction-free implementation. We elaborate herein on the notions of obstruction-freedom and contention management, and various possibilities for combining the two. In addition, we include description of some exemplary applications to particular concurrent software mechanisms and data structure implementations.
摘要:
We propose a new form of software transactional memory (STM) designed to support dynamic-sized data structures, and we describe a novel non-blocking implementation. The non-blocking property we consider is obstruction-freedom. Obstruction-freedom is weaker than lock-freedom; as a result, it admits substantially simpler and more efficient implementations. An interesting feature of our obstruction-free STM implementation is its ability to use of modular contention managers to ensure progress in practice.
摘要:
We present a technique for implementing obstruction-free atomic multi-target transactions that target special “transactionable” locations in shared memory. A programming interface for using operations based on these transactions can be structured in several ways, including as n-word compare-and-swap (NCAS) operations or as atomic sequences of single-word loads and stores (e.g., as transactional memory).
摘要:
We explore techniques for designing nonblocking algorithms that do not require advance knowledge of the number of processes that participate, whose time complexity and space consumption both adapt to various measures, rather than being based on predefined worst-case scenarios, and that cannot be prevented from future memory reclamation by process failures. These techniques can be implemented using widely available hardware synchronization primitives. We present our techniques in the context of solutions to the well-known Collect problem. We also explain how our techniques can be exploited to achieve other results with similar properties; these include long-lived renaming and dynamic memory management for nonblocking data structures.
摘要:
We propose a new form of software transactional memory (STM) designed to support dynamic-sized data structures, and we describe a novel non-blocking implementation. The non-blocking property we consider is obstruction-freedom. Obstruction-freedom is weaker than lock-freedom; as a result, it admits substantially simpler and more efficient implementations. An interesting feature of our obstruction-free STM implementation is its ability to use of modular contention managers to ensure progress in practice.
摘要:
Solutions to a value recycling problem facilitate implementations of computer programs that may execute as multithreaded computations in multiprocessor computers, as well as implementations of related shared data structures. Some exploitations allow non-blocking, shared data structures to be implemented using standard dynamic allocation mechanisms (such as malloc and free). Some exploitations allow non-blocking, indeed even lock-free or wait-free, implementations of dynamic storage allocation for shared data structures. In some exploitations, our techniques provide a way to manage dynamically allocated memory in a non-blocking manner without depending on garbage collection. While exploitations of solutions to the value recycling problem that we propose include management of dynamic storage allocation wherein values managed and recycled tend to include values that encode pointers, they are not limited thereto. Indeed, the techniques are more generally applicable to management of values in a multithreaded computation. For example, value recycling techniques may be exploited, in some cases, apart from dynamic storage allocation, to allow a multithreaded computation to avoid the classic ABA hazard.
摘要:
Solutions to a value recycling problem that we define herein facilitate implementations of computer programs that may execute as multithreaded computations in multiprocessor computers, as well as implementations of related shared data structures. Some exploitations of the techniques described herein allow non-blocking, shared data structures to be implemented using standard dynamic allocation mechanisms (such as malloc and free). Indeed, we present several exemplary realizations of dynamic-sized, non-blocking shared data structures that are not prevented from future memory reclamation by thread failures and which depend (in some implementations) only on widely-available hardware support for synchronization. Some exploitations of the techniques described herein allow non-blocking, indeed even lock-free or wait-free, implementations of dynamic storage allocation for shared data structures. A class of general solutions to value recycling is described in the context of an illustration we call the Repeat Offender Problem (ROP), including illustrative Application Program Interfaces (APIs) defined in terms of the ROP terminology. Furthermore, specific solutions, implementations and algorithm, including a Pass-The-Buck (PTB) implementation are described.
摘要:
We introduce obstruction-freedom—a new non-blocking condition for shared data structures that weakens the progress requirements of traditional nonblocking conditions, and as a result admits solutions that are significantly simpler and more efficient in the typical case of low contention. We demonstrate the merits of obstruction-freedom by showing how to implement an obstruction-free double-ended queue that has better properties than any previous nonblocking deque implementation of which we are aware. The beauty of obstruction-freedom is that we can modify and experiment with the contention management mechanisms without needing to modify (and therefore reverify) the underlying non-blocking algorithm. In contrast, work on different mechanisms for guaranteeing progress in the context of lock-free and wait-free algorithms has been hampered by the fact that modifications to the “helping” mechanisms has generally required the proofs for the entire algorithm to be done again.