linux是否调度进程或线程? [英] Does linux schedule a process or a thread?

问题描述

在阅读这个 SO问题后，我有些疑问.请帮助理解.

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

计划涉及确定何时运行流程以及运行时间的时间.

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

1. Linux内核是否调度线程或进程?由于内核中的进程和线程没有区别，因此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?

如何确定每个线程的量子量? 一种.如果为一个进程确定了一个时间量(例如100us)，是该进程的所有线程之间共享的时间吗?或者 b.每个线程的数量由调度程序决定吗?

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的进展方式，在这里都将它们都贴了.

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(至少在最新的Linux内核上，例如3.0)正在调度可调度任务或只是 tasks .

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

任务可能是:

• 单线程进程(例如，由fork创建，没有任何线程库)
• 多线程进程中的任何线程(包括其主线程)，尤其是Posix线程(pthreads)
• 内核任务，这些任务在内核内部启动并停留在内核领域(例如kworker，nfsiod，kjournald，kauditd，kswapd等，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，多线程进程内部的线程的调度方式类似于非线程-i.单线程进程.

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

clone(2)底层系统调用用户级可调度任务(可用于创建fork -ed进程或用于实现线程库，例如 pthread ).除非您是低级线程库实现者，否则您不希望直接使用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，而是内部的每个线程(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，在调度中有一些线程组概念和 affinity ，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，处理器通常具有多个内核，并且每个内核都正在运行一个任务(在给定的瞬间)，因此您确实有多个并行运行的任务.

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量子时间分配给任务，而不是进程

CPU quantum times are given to tasks, not to processes

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