SSD6名词解释(个人完善版)

SSD6名词解释
1. alignment（对齐）
Compilers often try to align data word boundaries or even double-word or even double-word boundaries.
(计算机系统对基本数据类型的可允许地址做出的限制，要求某种类型的对象地址必须是某个值K（2,4,8）的倍数。

2. activation record（活动记录）
The chunk of memory allocated for each function invocation .
大块的内存分配为每个函数调用
3. buffer overflow（缓存溢出）
Place more than the buffer can hold, so overwrite the boundary .
4. static memory allocation（静态内存分配）
Static memory allocation is the allocation of memory storage during the compile time and link time (在程序编译和链接时分配内存)
5. dynamic memory allocation（动态内存分配）
Dynamic memory allocation is the allocation of memory storage during the runtime of program. （在程序运行时分配内存）
6. garbage collection （垃圾回收）
Automatic reclamation of heap-allocated storage .
自动回收堆存储的过程叫做垃圾回收。

垃圾收集器是一种动态存储分配器，它自动释放程序不再需要的已分配块。

7. timer（计时器）
A component in computer system/CS, as a hardware or software, which can provide the ability of measure time in some degree.
计算机系统的组件，可以是硬件或者软件，能够提供某种精度上的时间的测量。

8. walltime（挂钟时间）
Wall clock time is the time an ordinary clock on the wall or a wrist watch shows.
实际上就是指实际时间。

9. CPUtime
（包含两部分时间，一个是CPU 用户时间，还有一个是CPU系统时间，用户时间指用来执行用户代码的时间，而系统时间指，操作系统执行一系列指令所耗费的时间）
CPU time = user CPU time + system CPU time
CPU user time: the CPU time spent directly executing your program code,
CPU system time: the CPU time spent by the operating system on behalf of your program 10．Profiling(抽样统计)
（抽样统计用于帮助程序员鉴别，程序的那个部分是导致导致运行缓慢的瓶颈；哪部分程序调用的频率最高）
Profiling is used to help programmers to identify:
which areas of the program are causing sluggish bottlenecks.
which parts of the code are being called the most often.
11．SRAM:
Static RAM (SRAM) Static Random Access Memory
构成：Each cell stores bit with a six-transistor circuit.
·Retains value indefinitely, as long as it is kept powered.
·Relatively insensitive to disturbances such as electrical noise.
·Faster and more expensive than DRAM.
（每个存储单元有六个晶体管电路控制，相对稳定，不容易受电子噪声的干扰，只要不断电，就会保存所存储的内容，比DRAM更快，但是更贵。

）
12．DRAM
Dynamic RAM (DRAM) Dynamic Random Access Memory
·构成：Each cell stores bit with a capacitor and transistor.
·Value must be refreshed every 10-100 ms.
·Sensitive to disturbances.
·Slower and cheaper than SRAM.
（DRAM每个存储单元由一个电容器和晶体管组成，对周围的环境比较敏感，容易受到电子噪声干扰，但是比SRAM慢，相对比较便宜。

）
13．memory hierarchy（存储器的层次结构）
The computer system is not to rely on a single memory component or technology but to employ a memory hierarchy. Thus, smaller, more expensive, faster memories are supplemented by larger, cheaper, slower memories. The key to the success of this organization is the last item: decreasing frequency of access.
计算机系统不是依赖于单一的存储组件或技术，而是使用存储器的层次结构。

容量较大、价格较便宜的慢速存储器是容量较小、价格较贵的快速存储器的后备。

这种存储器的层次结构能够成功的关键在于最后一种情况：处理器访问存储器的频率递减。

14．locality（局部性）
Memory addresses that have been accessed recently are likely to be accessed again. This is often called the principle of locality of reference.
According to this principle, all programming results in patterns of memory access in which: (1) References to a single address occur close together in time (this is called temporal locality). Temporal locality entails that addresses that are referenced are soon referenced repeatedly, and should thus be kept in fast memory.
(2) References to addresses that are near to(位置) each other occur together in time (this is called spatial locality). Spatial locality addresses will soon be accesses near a referenced address will soon be accessed and should thus be brought into fast memory.
局部性原理：程序倾向于引用的数据项邻近于其他最近引用过的数据，或者邻近于最近自我引用过的数据项。

局部性通常有两种，时间局部性和空间局部性，
对于时间局部性，被引用过一次的存储器位置很可能在不远的将来再被多次引用。

对于空间局部性：如果一个存储器位置被引用了一次，那么程序很可能在不远的将来引用附近的一个存储器位置。

15．linking
Linking is the process of collecting and combining the various pieces of code and data that a program needs in order to be loaded (copied) into memory and executed 。

链接就是将不同部分的代码和数据收集和组合成为一个单一文件的过程，这个文件可被加载到存储器并执行。

16．linker(链接器)
连接器是一个系统程序，它把编译产生的多个文件结合成一个可执行文件
Linker or link editor is a program that takes one or more objects generated by a compiler and combines them into a single executable program.
17．symbol resolution
Symbol Resolution/符号解析：Object files define and reference symbols. The purpose of symbol resolution is to associate each symbol reference with exactly one symbol definition.
Symbol resolution:
(1) The linker associates each reference with exactly one symbol definition
(2) References to local symbols defined in the same module is straightforward
(3) Resolving references to global variables is trickier
（将每个引用与它输入的可重定位目标文件的符号表中的一个确定的符号定义联系起来）18．relocation（重定位）
Relocation/重定位：Compilers and assemblers generate code and data sections that start at address zero. The linker relocates these sections by associating a memory location with each symbol definition, and then modifying all of the references to those symbols so that they point to this memory location.
（合并输入模块，并为每个符号分配运行时地址，重定位分为两步：○1重定位节和符号定义○2重定位节中的符号引用）
19．loading
Loading is the process of copying the program into memory and then running it.
将程序拷贝到主存并执行。

20．loader
A loader is a system program that performs the loading function (_execve). Some systems have a linker to perform the linking and a separate loader to handle relocation and loading. Some systems blurs the distinction between the compile-time process and the run-time process, many loaders also support relocation and linking.
一个执行加载功能的系统程序。

21．exception（异常）:
an exeption is an abrupt change in the control flow in response to some change in the processor’s state.(异常就是控制流中的突变，用来响应处理器状态中的某些变化)
22．exceptional control flow(ECF)（异常控制流）
ECF refers to abrupt control transfers to react to changes in system state 。

ECF就是控制流中的突变，用来响应处理器状态中的某些变化。

23．process（进程）
a process is an instance of a program in execution.
(进程最经典的定义就是一个执行中程序的实例)。

24．thread（线程）：
thread is a logical Flow of Control/Trace/Execution path in the space of one process 25．concurrency(并发)
concurrent program is a collection of autonomous(自主的) sequential threads, executing (logically) in parallel .
26．synchronization（同步）
Synchronization refers to the ability of multiple processes (or threads) to coordinate their activities by the exchange of information
多个进程相互交换信息相互共同协作。

27．mutual exclusion（互斥）
Mutual exclusion refers to the ability of multiple processes (or threads) to share code, resources, or data in such a way that only one process has access to the shared object at a time
在同一段时间，只允许一个进程访问共享代码，资源。

28．critical section（临界区）
critical section is a piece of code that accesses a shared resource (data structure or device) that must not be concurrently accessed by more than one thread of execution.
临界区是一段访问共享资源的代码，当另一个进程已经在这段代码中运行时，这个进程就不能在这段代码中运行。

29．starvation（饥饿）
a situation in which a runnable process is overlooked indefinitely by the scheduler,although it is able to process,it is never chosen.
(饥饿是指一个可运行的进程尽管能继续执行，但被调度器无限期地忽视，而不能被调度执行的情况)
30．deadlock（死锁）
deadlock refers to a collection of threads are blocked,waiting for a condition that will never be true.
两个或者两个以上的进程在执行过程中，因争夺资源而造成一种相互等待的现象，如果没有外力作用，这个状态将会一直持续下去，产生的结果就是死锁。

31．Kenel object（内核对象）
Each kernel object is simply a memory block allocated by the kernel and is accessible only by the kernel. This memory block is a data structure whose members maintain information about the object.
每个内核对象都是由内核分配的并且只能被内核访问的内存块，这个内存块上维护着对象的信息，比如进程对象，线程对象，时间对象…..。