聊聊Linux内核进程调度上篇

// 省略大部分字段，着重描述下运行队列中的一些字段
struct rq {
	// 每个CPU的运行队列的锁
	raw_spinlock_t		lock;
	// 运行队列的进程数
	unsigned int		nr_running;
	// 当前CPU上的负载
	struct load_weight	load;
	// 进程切换的次数
	u64			nr_switches;
	// 公平调度器
	struct cfs_rq		cfs;
	// 实时调度器
	struct rt_rq		rt;
	// deadline调度器
	struct dl_rq		dl;

	unsigned long		nr_uninterruptible;
	// 正在运行的进程任务
	struct task_struct	*curr;
	// 空闲的进程任务
	struct task_struct	*idle;
	// 停止的进程任务
	struct task_struct	*stop;
	unsigned long		next_balance;
};

static void __sched notrace __schedule(bool preempt)
{
	next = pick_next_task(rq, prev, &rf);
}
 // 选择一个优先级最高的进程执行
static inline struct task_struct *pick_next_task(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
{
	const struct sched_class *class;
	struct task_struct *p;


	if (likely((prev->sched_class == &idle_sched_class ||
		    prev->sched_class == &fair_sched_class) &&
		   rq->nr_running == rq->cfs.h_nr_running)) {

		p = fair_sched_class.pick_next_task(rq, prev, rf);
		if (unlikely(p == RETRY_TASK))
			goto again;

		if (unlikely(!p))
			p = idle_sched_class.pick_next_task(rq, prev, rf);

		return p;
	}

again:
	for_each_class(class) {
		p = class->pick_next_task(rq, prev, rf);
		if (p) {
			if (unlikely(p == RETRY_TASK))
				goto again;
			return p;
		}
	}

	BUG();
}