计算机英语(第四版).2.5.-作者：刘兆毓、郑家农(普通高等教育“十一五”国家级规划教材).ppt

PART 1 COMPUTER HARDWARE CHAPTER 2 COMPUTER OPERATING SYSTEM,2-5 A CACHING MODEL OF OPERATING SYSTEM KERNEL FUNCTIONALITY,2-5 A CACHING MODEL OF OPERATING SYSTEM KERNEL FUNCTIONALITY,Main Point Insufficiencies of micro-kernels in operating system Introduction to an alternative approach to kernet design on a caching model,KEYWORDS,caching model 高速缓存模型 micro-kernel 微内核 monolithic 单块（片）的 virtual memory system 虚拟存储系统 copy-on-write 按写拷贝 domain-specific 特定域 resource allocation 资源分配 random access 随机访问,sequential access 顺序访问 resource management 资源管理 failure 故障，失效 application module 应用模块 server 服务器 active object 活动对象 address space 地址空间 thread 线程,Inter-Process Communication (IPC) 进程间通信 mapping 映像，镜像 descriptor 描述符 page frame 页面帧 supervisor-level 管理层 programming interface 编程接口 emulator 仿真器,Micro-kernels to date have not provided compelling advantages over the conventional monolithic operating system kernel for several reasons. First, micro-kernels are larger than desired because of the complications of a modern virtual memory system (such as the copy-on-write facility), the need to support many different hardware devices, and complex optimizations in communication facilities, all of which have been handled inside most micro-kernels. 1,原因状语,原因状语,原因状语,非限定性定语从句,Moreover, performance problems have tended to force services originally implemented on top of a micro-kernel back into the kernel, increasing its size. 2 Second, micro-kernel do not support domain-specific resource allocation policies any better than monolithic kernels, an increasingly important issues with sophisticated applications and application systems. 3 For example, the standard page-replacement policies of UNIX-like operating systems perform poorly for applications with random or,定语,结果状语,比较,同位语,sequential access. Placement of conventional operating system kernel services in a micro-kernel-based does not generally give the applications any more control because the server is a fixed protected system service. 4 Adding a variety of resource management policies to the micro-kernel fails to achieve the efficiency that application-specific knowledge allows and increases the kernel size and complexity. 5,宾语补语,原因状语从句,主语,谓语,原因状语从句,Finally, micro-kernels are bloated with exception-handling mechanisms for the failure and unusual cases that can arise with the hardware and with other server and application modules. 6 For example, the potential page-in exception conditions with external pagers introduces complications into machine.,原因状语,定语从句,原因状语,?1 List three reasons that micro-kernels have not provided compeling advantages over the conventional monolithic operating kernel ?,In this paper, we present an alternative approach to kernel design based on a caching model, as realized in the V+ Cache Kernel. The V+ Cache Kernel caches the active objects associated with the basic operating system facilities, namely the address spaces and threads associated with virtual memory, scheduling and IPC. In contrast to conventional micro-kernel design, it does not fully implement all the functionality associated with address spaces and threads. Instead, it relies on higher-level application,方式状语,同位语,kernels to provide the management functions required for a complete implementation, including the loading and write-back of these objects to and from the Cache Kernel. 7 For example, on a page fault, the application kernel associated with the faulting thread loads a new page mapping descriptor into the Cache Kernel as part of a cached address space object. This new descriptor may cause another page mapping descriptor to be written back to another application kernel to make space for the new descriptor.,状语,宾语补语,Because the application kernel selects the physical page frame to use, it fully controls physical page selection, the page replacement policy and paging I/O The following sections argue that this caching model reduces supervisor-level complexity, provides application control of resource management and provides application control over exception conditions and recovery, addressing the problems with microkernel designs to date (including a micro-kernel that we developed previously). 8,原因状语从句,宾语,宾语,宾语,宾语从句,谓语,谓语,谓语,状语,The next section describes the Cache Kernel programming interface, illustrating its use by describing how an emulator application kernel would use this interface to implement standard UNIX-like services. 9 Section 3 describes how sophisticated applications can use this interface directly by executing as part of their own application kernel. Section 3 describes how resources are allocated among competing applications. Section 4 describes our Cache Kernel implementation, and Section 5,状语,方式状语,宾语从句,宾语从句,宾语从句,describes its performance, which appears to provide competitive performance with conventional monolithic kernels. Section 6 describes previous research we see as relevant to this work. We close with a summary of the work, our conclusions and some indication of future directions,非限定性定语从句,定语从句,?2 Point out the point described in following dix sections ?,NOTES,1 长句。Because of引导的原因状语由三部分组 成: all of which为非限定性定语从句。 2 implemented 过去分词短语作定语，修饰 services；increasing现在分词短语作结果状 语。 3 an increasingly important issues.同位语。 4 any more control是the applications宾语的补语； because引导的是原因状语从句。,5 Adding动名词短语作主语，fails为谓语，that引 导的是原因状语从句。 6 that引导的是定语从句，修饰cases. 7 本句和上一句中的it均指Caching model. 8 长句。that引导的宾语从句有三部分; addressing分词短语作状语。 9 句中有两个现在分词短语，一是illustrating作状 语，另一个是describing作方式状语，其中how 引导的是宾语从句。,EXERCISES,Multiple Choices 1.Modern virtual memory system . a. needs to support complex optimizations in communication facilities. b. includes copy-on-write facility. c. requires to support only one type of hardware device. d. requires to support many different hardware device.,a,b,d,2.Adding a variety of resource management policies to the micro-kernel . a. can achieve the efficiency b. can not achieve the efficiency c. can increase the kernel size d. can increase the kernel complexity,b,c,d,3. Cache Kernel programming interface can be used . a. by an emulator application kernel b. by sophisticated applications c. to implement standard UNIX-like services d. to execute as part of the sophisticated application kernel,a,b,c,d,4. Micro-kernels are bloated and complicated with . a. exception-handling mechanisms b. regular handling mechanisms c. potential page-in exception conditions d. external pages,a,c,d,5. Caching model has ability of . a. increasing supervisor-level complexity b. reducing supervisor-level complexity c. providing application control of resource management d. providing application control over exception conditions,b,c,d,6. The reasons that the micro-kernels to date have not provided compelling advantages over the conventional monolithic operating system kernel are . a. Micro-kernels do not support domain-specific resource allocation policies any better than monolithic kernels b. Micro-kernels are larger than desired c. Micro-kernels are bloated with exception- handling mechanisms d. Micro-kernels are complex with page-in exception conditions and external pagers,a,b,c,d,7. The standard page-replacement policies of UNIX-like operating system . a. are an increasingly important problems with sophisticated applications b. perform poorly for applications with random access c. perform poorly for applications with sequential access d. are an increasingly important problems with application systems,a,b,c,d,8. The V+ Cache Kernel . a. fully implements all the functionality associated with address spac