英文：9250字
中文：3153字

Process Management

The process is one of the fundamental abstractions in Unix operating systems. A process is a program(object code stored on some media) in execution. Processes are, however, more than just the executingprogram code (often called the text section in Unix). They also include a set of resources such as open files and pending signals, internal kernel data, processor state, an address space, one or more threads ofexecution, and a data section containing global variables. Processes, in effect, are the living result of running program code.
Threads of execution, often shortened to threads, are the objects of activity within the process. Each thread includes a unique program counter, process stack, and set of processor registers. The kernel schedules individual threads, not processes. In traditional Unix systems, each process consists of one thread. In modern systems, however, multithreaded programsthose that consist of more than one threadare common. Linux has a unique implementation of threads: It does not differentiate between threads and processes. To Linux, a thread is just a special kind of process.

進(jìn)程管理
進(jìn)程是Uinx操作系統(tǒng)最基本的抽象之一。一個進(jìn)程就是處于執(zhí)行期間的程序（目標(biāo)代碼放在某種存儲介質(zhì)上）。但進(jìn)程并不僅僅局限于一段可執(zhí)行程序（Unix稱其為代碼段（text section））。通常進(jìn)程還要包含其他資源，像打開的文件、掛起的信號、內(nèi)核內(nèi)部數(shù)據(jù)、處理器狀態(tài)、地址空間及一個或多個執(zhí)行線程、當(dāng)然還包括用來存放全局變量的數(shù)據(jù)段等。實際上，進(jìn)程就是正在執(zhí)行的程序代碼的活標(biāo)本。
 執(zhí)行線程，簡稱線程（thread），是在進(jìn)程中活動的對象。每個線程用由一個獨立的程序計數(shù)器、進(jìn)程棧和一組進(jìn)程寄存器。內(nèi)核調(diào)度的對象是線程，而不是進(jìn)程。在傳統(tǒng)的Unix系統(tǒng)中，一個進(jìn)程只包含一個線程，但現(xiàn)在的系統(tǒng)中，包含多個線程的多線程程序司空見慣。Linux系統(tǒng)的線程實現(xiàn)非常特別—他對線程和進(jìn)程并不特別區(qū)分。對Linux而言，線程只不過是一種特殊的進(jìn)程罷了。
 在現(xiàn)代操作系統(tǒng)中，進(jìn)程提供兩種虛擬機(jī)制：虛擬處理器和虛擬內(nèi)存。雖然實際上可能是許多進(jìn)程正在分享一個處理器，但虛擬處理器給進(jìn)程一種假象，讓這些進(jìn)程覺得自己在獨享處理器。而虛擬內(nèi)存讓進(jìn)程在獲取和使用內(nèi)存是覺得自己擁有整個操作系統(tǒng)的所有內(nèi)存資源。有趣的是，注意在線程之間（這里是指包含在同一個進(jìn)程中的進(jìn)程）可以共享虛擬內(nèi)存，但擁有各自的虛擬處理器。