A Retrospective on Region-Based Memory Management

We report on our experience with designing, implementing, proving correct, and evaluating a region-based memory management system.     

Nonintrusive Cloning Garbage Collection with Stock Operating System Support

It is well accepted that automatic garbage collection simplifies programming, promotes modularity, and reduces development effort. However it is commonly believed that these advantages do not counteract the perceived price: excessive overheads, possible long pause times while garbage collections occur, and the need to modify existing code. Even though there are publically available garbage collector implementations that can be used in existing programs, they do not guarantee short pauses, and some modification of the application using them is still required. In this paper we describe a snapshot-at-beginning concurrent garbage collector algorithm and its implementation. This algorithm guarantees short pauses, and can be easily implemented on stock UNIX-like operating systems. Our results show that our collector performs comparable to other garbage collection implementations on uniprocessor machines and outperforms similar collectors on multiprocessor machines. We also show our collector to be competitive in performance with explicit deallocation. Our collector has the added advantage of being non-intrusive. Using a dynamic linking technique and effective root set inferencing, we have been able to successfully run our collector even in commercial programs where only the binary executable and no source code is available. In this paper we describe our algorithm, its implementation, and provide both an algorithmic and a performance comparison between our collector and other similar garbage collectors. ©1997 by John Wiley & Sons, Ltd.     

气象卫星资料虚拟存储系统设计与实现

利用服务器连接（SAS）技术和存储局域网（SAN）技术构建气象卫星资料存储系统。实现群集环境中计算机系统间的存储资源共享,设计虚拟存储管理软件对不同的物理存储设备进行逻辑管理,可以简化存储设备的使用,可以提高系统运行效率,国家卫星气象中心的气象卫星资料存储系统的运行结果表明,虚拟存储是解决群体环境中不同物理存储设备有效使用的一条切实可行的技术路线。     

The implementation of generic smart pointers for advanced defensive programming

Smart pointers denote a well‐known technique for collective resource ownership, e.g. sharing dynamic object instances, while usually supporting automatic garbage collection based on reference counting. The original method has been retargeted to serve as a generic defensive programming method for ‘exhaustive tracking’ of erroneous pointer use in C++. Automatic bug tracking is supported in a unified manner both for pointers to heap memory, i.e. free storage, as well as for pointers to stack or global memory, i.e. auto or static storage. Overall, the presented technique (a) offers a simple contract for memory allocation and use; (b) supports type and indirection depth genericity; (c) implements most operators supported for built‐in pointers with embedded bug defense; (d) offers an alternative way of employing a garbage collection facility for memory leak detection; and (e) provides an appropriate collection of utility macros, through which defensive pointers should be used, with an alternative version re‐targeted to normal native pointers. Copyright © 2004 John Wiley & Sons, Ltd.     

A portable storage management system for the icon programming language

Icon is a new programming language designed primarily for non-numerical applications. Its roots are in SNOBOL4 and SL5; as in those languages, execution-time flexibility is an important attribute of Icon, although some aspects of programs are bound at compile time to improve efficiency. Icon, which is implemented in Ratfor, is also intended to be portable and suitable for 16-bit computers. The storage management system in Icon is designed to meet the goals of portability, flexibility and efficiency. This is accomplished by subdividing the storage management system into a set of type-specific storage management subsystems. This paper describes the implementation of these subsystems, their interaction, and their performance.     

The measured cost of conservative garbage collection

Because dynamic memory management is an important part of a large class of computer programs, high-performance algorithms for dynamic memory management have been, and will continue to be, of considerable interest. Experience indicates that for many programs, dynamic storage allocation is so important that programmers feel compelled to write and use their own domain-specific allocators to avoid the overhead of system libraries. As an alternative to explicit storage management techniques, conservative garbage collection has been suggested as an important algorithm for dynamic storage management in C programs. In this paper, I evaluate the costs of different dynamic storage management algorithms, including domain-specific allocators, widely-used general-purpose allocators, and a publicly available conservative garbage collection algorithm. Surprisingly, I find that programmer enhancements often have little effect on program performance. I also find that the true cost of conservative garbage collection is not the CPU overhead, but the memory system overhead of the algorithm. I conclude that conservative garbage collection is a promising alternative to explicit storage management and that the performance of conservative collection is likely to improve in the future. C programmers should now seriously consider using conservative garbage collection instead of explicitly calling free in programs they write.     

一种内存管理技术的研究与实现

内存管理在计算机系统设计中是及其重要且必须的部分.高效的内存分配,垃圾回收和整理,在并行,分布式和实时应用中变的越来越重要.提出了一种利用二叉树来管理可利用内存分区的算法,并通过试验得出的数据分析,表明为什么该方法比其它算法更为方便高效,实现起来也比较简单易行.     

内存数据库中存储结构的实现机制

内存数据库是外存数据库的"工作版本",它们无论在数据上、结构上等都应该保持一致性.怎么定义内存数据库的存储结构,特别当外存数据库中表的结构发生改变时,内存数据库中表结构的相应改变,都直接影响系统的性能.研讨了内存数据库结构的定义以及实现,并对静态和动态存储结构的机制作了详尽的分析,突出地反映了动态特性.     

仓储管理中的RFID中间件设计

针对无线射频识别(RFID)技术在仓储管理中的应用,探讨如何设计RFID中间件的问题.采用数据过滤,数据聚合,添加业务逻辑处理、查询支持等方法,将数据流转换为适合上层应用程序的逻辑形式,实现仓储管理的自动化、智能化.     

基于三方传送的存储管理系统设计与实现

存储系统已由NAS向SAN发展,如何融合NAS和SAN技术,提高存储系统的可管理性和性能,是目前存储领域研究的热点。提出了一种扩展文件共享的方法,采用三方传送机制来融合NAS和SAN,通过存储管理器和存储服务器的功能划分,由存储管理器负责存储设备的空间和文件的管理,存储服务器能共享SAN中的存储设备以及直接访问存储设备上的数据。该系统采用Lease协议来保证存储服务器端数据一致性,在此基础上分析了Lease协议模型。     

基于垃圾回收的三维引擎内存管理系统

本文面向三维引擎的上层内存管理,提出了一种基于垃圾回收算法的管理系统,辅助三维引擎使用者回收循环引用的内存.该系统基于由库的形式提供,并且不需要用户修改现有代码.用户只需要使用系统提供的接口创建对象,系统就能够在必要时自动回收内存.测试表明,本系统在可接受的开销下实现了循环引用内存的回收.     

仓储仿真三维图元管理平台

在仓储仿真项目的开发中,图元的创建和三维场景的布置是重要的步骤。为了简化仓储仿真项目的开发,提出一种仓储三维仿真图元管理的平台方案。该平台模型由4个关键模块组成。并在WPF下实现了关键模块,结果表明采用该平台的相应模块能够实现仿真图元对象的快速创建、仿真图元的高效管理,方便地为开发基于WPF平台的仓储仿真项目提供合适的图元对象。因此该平台能够简化仓储仿真项目的开发步骤。节省开发时间。     

网络测试数据存储MIB设计与实现

传统基于文件存储的大规模网络测试系统存在设计复杂、实时性差等不足．本文设计并实现了一个用于存储网络测试数据的管理信息库．基于该管理信息库存储数据的测试系统，使用标准的简单网络管理协议通信，可降低测试数据读写设计的复杂性，并保证测试数据传输的实时性，解决了网络测试系统文件存储方式存在的不足．     

JFFS2文件系统闪存管理策略研究与改造

本文通过分析JFFS2闪存日志文件系统闪存管理过程,发现了其现有垃圾回收算法的某些不足,讨论并提出了一种解决这些不足的方法,最后给出了改进的实现过程。     

信任管理系统中证书的分布式存储

对信任管理系统中证书的分布式存储问题进行了研究,分析了现有信任管理系统分布式存储方案存在的不足,提出一种新的证书分布式存储方案,通过由证书的接受者存放颁发给自己的证书,既实现了证书存储的分布性,又消除了现有方案中存在的瓶颈问题.方案设计简单,查找证书准确、快速,能够以不同模式进行查找,无需对现有证书格式进行修改,适用于多种现有信任管理系统的证书分布式存储.     

Implementation of a constant‐time dynamic storage allocator

This paper describes the design criteria and implementation details of a dynamic storage allocator for real‐time systems. The main requirements that have to be considered when designing a new allocator are concerned with temporal and spatial constraints. The proposed algorithm, called TLSF (two‐level segregated fit), has an asymptotic constant cost, O(1), maintaining a fast response time (less than 200 processor instructions on a x86 processor) and a low level of memory usage (low fragmentation). TLSF uses two levels of segregated lists to arrange free memory blocks and an incomplete search policy. This policy is implemented with word‐size bitmaps and logical processor instructions. Therefore, TLSF can be categorized as a good‐fit allocator. The incomplete search policy is shown also to be a good policy in terms of fragmentation. The fragmentation caused by TLSF is slightly smaller (better) than that caused by best fit (which is one of the best allocators regarding memory fragmentation). In order to evaluate the proposed allocator, three analyses are presented in this paper. The first one is based on worst‐case scenarios. The second one provides a detailed consideration of the execution cost of the internal operations of the allocator and its fragmentation. The third analysis is a comparison with other well‐known allocators from the temporal (number of cycles and processor instructions) and spatial (fragmentation) points of view. In order to compare them, a task model has been presented. Copyright © 2007 John Wiley & Sons, Ltd.     

内容管理系统存储层的设计与实现

为有效达到内容管理系统在海量数据的存储,以及在高并发请求下仍能快速响应用户的请求的目的,在研究了传统存储管理方式和分析了在系统中使用关系数据库将会遇到的问题后,采用开源软件Hadoop作为底层分布式存储基础,设计和实现了此时的内容管理系统的存储层,以满足系统快速读取内容的需求。介绍了系统的内容组织管理模型,针对系统快速读写内容的需求,对读写机制进行了改进、优化和封装,并通过实验测试来验证正确性和可行性。     

基于策略的对象存储文件系统管理模型研究

基于对象存储文件系统结构特点和策略管理思想,提出了对象存储文件系统管理的一般模型.定义了两种策略结构,并通过分析对象存储文件系统节点状态转换逻辑关系,给出了管理策略订制的理论依据.模型及其管理策略订制方法在Lustre对象存储文件系统中得到应用,效果良好.     

浅析.NET的垃圾回收机制

.NET Framework中的垃圾回收(Garbage Collection)机制减少了一些应用程序中发生内存泄露和访问冲突的可能性,但GC的工作机制仍然存在问题。在程序开发中,总会发现对于GC的错误理解。文章针对此问题进行研究分析,简要说明内存垃圾的产生原因、垃圾回收机制的原理、垃圾回收的主要对象以及释放模式。