Linux内核如何在多个内核之间迁移进程? [英] How does Linux kernel migrate the process among multiple cores?

问题描述

上下文:

进程1在核心0上执行.Core-1处于空闲状态.

Process-1 is executing on core-0. Core-1 is idle.

现在，进程1使用 sched_setaffinity()更改其CPU亲和性为core-1.

Now, process-1 uses sched_setaffinity() to change its CPU affinity as core-1.

问题:

哪些内核函数将process-1迁移到core-1上执行?

Which kernel function(s) migrate the process-1 to execute on core-1?

推荐答案

以下是从内核中的 sched_setaffinity 系统调用入口点开始的调用序列:

Here is the call sequence starting from the sched_setaffinity system call entry point in the kernel:

1. sys_sched_setaffinity .
>
2. sched_setaffinity .
>
3. __set_cpus_allowed_ptr .
>

在最后一个函数中，有两种情况，如第1101行:

In the last function, there are two cases as shown in the code at line 1101:

if (task_running(rq, p) || p->state == TASK_WAKING) {
    // ...
    stop_one_cpu(cpu_of(rq), migration_cpu_stop, &arg);
    // ...
} else if (task_on_rq_queued(p)) {
    rq = move_queued_task(rq, &rf, p, dest_cpu);
}

如果要迁移的任务当前正在运行或正在唤醒，则可以通过调用 stop_one_cpu 来迁移它，该命令依次调用以下函数:

If the task to be migrated is currently running or waking up, then it is migrated by calling stop_one_cpu, which calls the following functions in order:

1. migration_cpu_stop .
>
2. __migrate_task .
>
3. moque_queued_task .
>

最后一个函数 move_queued_task 是将任务从当前运行队列实际移动到目标运行队列的函数.请注意，这是从 __ set_cpus_allowed_ptr 的另一个分支调用的函数.该分支处理任务处于其他任何状态的情况.

The last function, move_queued_task, is the one that actually moves the task from the current runqueue to the target runqueue. Note that this is the same function that is called from the other branch of __set_cpus_allowed_ptr. That branch handles the case where the task is in any of the other states.

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