linux 是调度进程还是线程? [英] Does linux schedule a process or a thread?

问题描述

在阅读这个 SO 问题后，我有一些疑问.请帮助理解.

After reading this SO question I got a few doubts. Please help in understanding.

调度涉及决定何时运行进程以及运行多长时间.

Scheduling involves deciding when to run a process and for what quantum of time.

1. linux 内核是调度线程还是进程?由于进程和线程在内核内部没有区别，调度程序如何处理它们?

1. Does linux kernel schedule a thread or a process? As process and thread are not differentiated inside kernel how a scheduler treats them?

每个线程的量是如何决定的?一个.如果为一个进程确定了一个时间量(比如 100us)，是否在进程的所有线程之间共享?或者湾每个线程的量程是由调度程序决定的吗?

How quantum for each thread is decided? a. If a quantum of time (say 100us) is decided for a process is that getting shared between all the threads of the process? or b. A quantum for each thread is decided by the scheduler?

注意:问题 1 和问题 2 是相关的，可能看起来相同，但只是想弄清楚事情是如何运作的，将它们都张贴在这里.

Note: Questions 1 and 2 are related and may look the same but just wanted to be clear on how things are working posted them both here.

推荐答案

Linux 调度程序(在最近的 Linux 内核上，例如至少 3.0)正在调度可调度任务或简单地任务em>.

The Linux scheduler (on recent Linux kernels, e.g. 3.0 at least) is scheduling schedulable tasks or simply tasks.

一个任务可能是:

• 单线程进程(例如由fork创建，没有任何线程库)
• 多线程进程内的任何线程(包括其主线程)，尤其是 Posix 线程(pthread)
• 内核任务，在内核内部启动并留在内核空间(例如 kworker、nfsiod、kjournald、kauditd, kswapd 等等...)

• a single-threaded process (e.g. created by fork without any thread library)
• any thread inside a multi-threaded process (including its main thread), in particular Posix threads (pthreads)
• kernel tasks, which are started internally in the kernel and stay in kernel land (e.g. kworker, nfsiod, kjournald , kauditd, kswapd etc etc...)

换句话说，多线程进程中的线程被调度为非线程的——即单线程进程.

In other words, threads inside multi-threaded processes are scheduled like non-threaded -i.e. single threaded- processes.

低级 clone(2) 系统调用创建用户级可调度任务(可用于创建 fork 处理的进程或用于实现线程库，如 pthread).除非你是一个低级线程库实现者，否则你不想直接使用clone.

The low-level clone(2) syscall creates user-land schedulable tasks (and can be used both for creating fork-ed process or for implementation of thread libraries, like pthread). Unless you are a low-level thread library implementor, you don't want to use clone directly.

AFAIK，对于多线程进程，内核(几乎)不是在调度进程，而是在内部的每个单独线程(包括主线程).

AFAIK, for multi-threaded processes, the kernel is (almost) not scheduling the process, but each individual thread inside (including the main thread).

^{实际上，调度中有一些线程组和affinity的概念，但我不太了解他们}

^{Actually, there is some notion of thread groups and affinity in the scheduling, but I don't know them well}

如今，处理器通常有多个内核，每个内核都在运行一项任务(在某个给定时刻)，因此您确实有多个任务并行运行.

These days, processors have generally more than one core, and each core is running a task (at some given instant) so you do have several tasks running in parallel.

CPU 时间分配给任务，而不是给进程

CPU quantum times are given to tasks, not to processes

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