Linux 内核调度器类框架分析
1. struct sched_class 结构体定义
文件: kernel/sched/sched.h行号: 2500-2661
c
struct sched_class {
#ifdef CONFIG_UCLAMP_TASK
int uclamp_enabled;
#endif
/* 入队任务 */
void (*enqueue_task) (struct rq *rq, struct task_struct *p, int flags);
/* 出队任务 */
bool (*dequeue_task) (struct rq *rq, struct task_struct *p, int flags);
/* yield 相关 */
void (*yield_task) (struct rq *rq);
bool (*yield_to_task)(struct rq *rq, struct task_struct *p);
/* 抢占相关 */
void (*wakeup_preempt)(struct rq *rq, struct task_struct *p, int flags);
/* 负载均衡 */
int (*balance)(struct rq *rq, struct task_struct *prev, struct rq_flags *rf);
/* 选取任务 */
struct task_struct *(*pick_task)(struct rq *rq, struct rq_flags *rf);
struct task_struct *(*pick_next_task)(struct rq *rq, struct task_struct *prev,
struct rq_flags *rf);
/* 任务切换 */
void (*put_prev_task)(struct rq *rq, struct task_struct *p, struct task_struct *next);
void (*set_next_task)(struct rq *rq, struct task_struct *p, bool first);
/* 选择 CPU */
int (*select_task_rq)(struct task_struct *p, int task_cpu, int flags);
/* 任务迁移 */
void (*migrate_task_rq)(struct task_struct *p, int new_cpu);
/* 任务唤醒后处理 */
void (*task_woken)(struct rq *this_rq, struct task_struct *task);
/* CPU 亲和性设置 */
void (*set_cpus_allowed)(struct task_struct *p, struct affinity_context *ctx);
/* CPU 状态变更 */
void (*rq_online)(struct rq *rq);
void (*rq_offline)(struct rq *rq);
/* 查找可运行任务的 CPU */
struct rq *(*find_lock_rq)(struct task_struct *p, struct rq *rq);
/* 时钟tick处理 */
void (*task_tick)(struct rq *rq, struct task_struct *p, int queued);
void (*task_fork)(struct task_struct *p);
void (*task_dead)(struct task_struct *p);
/* 调度类切换钩子 */
void (*switching_from)(struct rq *this_rq, struct task_struct *task);
void (*switched_from) (struct rq *this_rq, struct task_struct *task);
void (*switching_to) (struct rq *this_rq, struct task_struct *task);
void (*switched_to) (struct rq *this_rq, struct task_struct *task);
/* 优先级相关 */
u64 (*get_prio) (struct rq *this_rq, struct task_struct *task);
void (*prio_changed) (struct rq *this_rq, struct task_struct *task, u64 oldprio);
/* 负载权重调整 */
void (*reweight_task)(struct rq *this_rq, struct task_struct *task,
const struct load_weight *lw);
/* RR 间隔获取 */
unsigned int (*get_rr_interval)(struct rq *rq, struct task_struct *task);
/* 运行时统计更新 */
void (*update_curr)(struct rq *rq);
#ifdef CONFIG_FAIR_GROUP_SCHED
void (*task_change_group)(struct task_struct *p);
#endif
#ifdef CONFIG_SCHED_CORE
int (*task_is_throttled)(struct task_struct *p, int cpu);
#endif
};2. 调度类注册与优先级顺序
2.1 调度类定义宏
文件: kernel/sched/sched.h行号: 2709-2712
c
#define DEFINE_SCHED_CLASS(name) \
const struct sched_class name##_sched_class \
__aligned(__alignof__(struct sched_class)) \
__section("__" #name "_sched_class")每个调度类被放置在独立的链接段中，通过 __section__ 编译器属性实现。
2.2 调度类实例声明
行号: 2715-2722
c
extern struct sched_class __sched_class_highest[];
extern struct sched_class __sched_class_lowest[];
extern const struct sched_class stop_sched_class;
extern const struct sched_class dl_sched_class;
extern const struct sched_class rt_sched_class;
extern const struct sched_class fair_sched_class;
extern const struct sched_class idle_sched_class;2.3 链接脚本中的排序
文件: include/asm-generic/vmlinux.lds.h行号: 153-162
c
#define SCHED_DATA \
STRUCT_ALIGN(); \
__sched_class_highest = .; \
*(__stop_sched_class) \
*(__dl_sched_class) \
*(__rt_sched_class) \
*(__fair_sched_class) \
*(__ext_sched_class) \
*(__idle_sched_class) \
__sched_class_lowest = .;2.4 调度类优先级顺序
| 优先级 | 调度类 | 说明 |
|---|---|---|
| 最高 | stop_sched_class | 停止任务（用于 CPU 热插拔、负载均衡等） |
| dl_sched_class | 期限调度任务 | |
| rt_sched_class | 实时任务（SCHED_FIFO/SCHED_RR） | |
| fair_sched_class | 完全公平调度器（CFS）任务 | |
| ext_sched_class | SCX BPF 调度器扩展（可选） | |
| 最低 | idle_sched_class | 空闲任务（swapper） |
3. 各调度类实现
3.1 stop_sched_class
文件: kernel/sched/stop_task.c:99-119
c
DEFINE_SCHED_CLASS(stop) = {
.enqueue_task = enqueue_task_stop,
.dequeue_task = dequeue_task_stop,
.yield_task = yield_task_stop,
.wakeup_preempt = wakeup_preempt_stop,
.pick_task = pick_task_stop,
.put_prev_task = put_prev_task_stop,
.set_next_task = set_next_task_stop,
.balance = balance_stop,
.select_task_rq = select_task_rq_stop,
.set_cpus_allowed = set_cpus_allowed_common,
.task_tick = task_tick_stop,
.prio_changed = prio_changed_stop,
.switching_to = switching_to_stop,
.update_curr = update_curr_stop,
};3.2 dl_sched_class
文件: kernel/sched/deadline.c:3406-3437
c
DEFINE_SCHED_CLASS(dl) = {
.enqueue_task = enqueue_task_dl,
.dequeue_task = dequeue_task_dl,
.yield_task = yield_task_dl,
.wakeup_preempt = wakeup_preempt_dl,
.pick_task = pick_task_dl,
.put_prev_task = put_prev_task_dl,
.set_next_task = set_next_task_dl,
.balance = balance_dl,
.select_task_rq = select_task_rq_dl,
.migrate_task_rq = migrate_task_rq_dl,
.set_cpus_allowed = set_cpus_allowed_dl,
.rq_online = rq_online_dl,
.rq_offline = rq_offline_dl,
.task_woken = task_woken_dl,
.find_lock_rq = find_lock_later_rq,
.task_tick = task_tick_dl,
.task_fork = task_fork_dl,
.get_prio = get_prio_dl,
.prio_changed = prio_changed_dl,
.switched_from = switched_from_dl,
.switched_to = switched_to_dl,
.update_curr = update_curr_dl,
};3.3 rt_sched_class
文件: kernel/sched/rt.c:2581-2611
c
DEFINE_SCHED_CLASS(rt) = {
.enqueue_task = enqueue_task_rt,
.dequeue_task = dequeue_task_rt,
.yield_task = yield_task_rt,
.wakeup_preempt = wakeup_preempt_rt,
.pick_task = pick_task_rt,
.put_prev_task = put_prev_task_rt,
.set_next_task = set_next_task_rt,
.balance = balance_rt,
.select_task_rq = select_task_rq_rt,
.set_cpus_allowed = set_cpus_allowed_common,
.rq_online = rq_online_rt,
.rq_offline = rq_offline_rt,
.task_woken = task_woken_rt,
.switched_from = switched_from_rt,
.find_lock_rq = find_lock_lowest_rq,
.task_tick = task_tick_rt,
.get_rr_interval = get_rr_interval_rt,
.switched_to = switched_to_rt,
.prio_changed = prio_changed_rt,
.update_curr = update_curr_rt,
};3.4 fair_sched_class
文件: kernel/sched/fair.c:13951-13980
c
DEFINE_SCHED_CLASS(fair) = {
.enqueue_task = enqueue_task_fair,
.dequeue_task = dequeue_task_fair,
.yield_task = yield_task_fair,
.yield_to_task = yield_to_task_fair,
.wakeup_preempt = wakeup_preempt_fair,
.pick_task = pick_task_fair,
.pick_next_task = pick_next_task_fair,
.put_prev_task = put_prev_task_fair,
.set_next_task = set_next_task_fair,
.select_task_rq = select_task_rq_fair,
.migrate_task_rq = migrate_task_rq_fair,
.rq_online = rq_online_fair,
.rq_offline = rq_offline_fair,
.task_dead = task_dead_fair,
.set_cpus_allowed = set_cpus_allowed_fair,
.task_tick = task_tick_fair,
.task_fork = task_task_fair,
.reweight_task = reweight_task_fair,
.prio_changed = prio_changed_fair,
.switching_from = switching_from_fair,
.switched_from = switched_from_fair,
.switched_to = switched_to_fair,
};3.5 idle_sched_class
文件: kernel/sched/idle.c:569-590
c
DEFINE_SCHED_CLASS(idle) = {
.dequeue_task = dequeue_task_idle,
.wakeup_preempt = wakeup_preempt_idle,
.pick_task = pick_task_idle,
.put_prev_task = put_prev_task_idle,
.set_next_task = set_next_task_idle,
.balance = balance_idle,
.select_task_rq = select_task_rq_idle,
.set_cpus_allowed = set_cpus_allowed_common,
.task_tick = task_tick_idle,
.prio_changed = prio_changed_idle,
.switching_to = switching_to_idle,
.update_curr = update_curr_idle,
};4. pick_next_task 遍历逻辑
文件: kernel/sched/core.c:5909-5964
c
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;
rq->dl_server = NULL;
if (scx_enabled())
goto restart;
/* CFS 快速路径：只有公平任务时直接调用 */
if (likely(!sched_class_above(prev->sched_class, &fair_sched_class) &&
rq->nr_running == rq->cfs.h_nr_queued)) {
p = pick_next_task_fair(rq, prev, rf);
if (unlikely(p == RETRY_TASK))
goto restart;
if (!p) {
p = pick_task_idle(rq, rf);
put_prev_set_next_task(rq, prev, p);
}
return p;
}
restart:
prev_balance(rq, prev, rf);
/* 遍历所有活跃调度类，从高优先级到低优先级 */
for_each_active_class(class) {
if (class->pick_next_task) {
p = class->pick_next_task(rq, prev, rf);
if (unlikely(p == RETRY_TASK))
goto restart;
if (p)
return p;
} else {
p = class->pick_task(rq, rf);
if (unlikely(p == RETRY_TASK))
goto restart;
if (p) {
put_prev_set_next_task(rq, prev, p);
return p;
}
}
}
BUG();
}迭代宏定义
文件: kernel/sched/sched.h:2740-2752
c
#define for_class_range(class, _from, _to) \
for (class = (_from); class < (_to); class++)
#define for_each_class(class) \
for_class_range(class, __sched_class_highest, __sched_class_lowest)
#define for_active_class_range(class, _from, _to) \
for (class = (_from); class != (_to); class = next_active_class(class))
#define for_each_active_class(class) \
for_active_class_range(class, __sched_class_highest, __sched_class_lowest)
#define sched_class_above(_a, _b) ((_a) < (_b))5. 调度类选择函数
文件: kernel/sched/core.c:7254-7266
c
const struct sched_class *__setscheduler_class(int policy, int prio)
{
if (dl_prio(prio))
return &dl_sched_class;
if (rt_prio(prio))
return &rt_sched_class;
#ifdef CONFIG_SCHED_CLASS_EXT
if (task_should_scx(policy))
return &ext_sched_class;
#endif
return &fair_sched_class;
}6. 核心设计思想
6.1 可插拔调度器抽象
sched_class 结构体通过函数指针定义了调度器的完整行为接口：
| 类型 | 函数指针 | 用途 |
|---|---|---|
| 任务队列 | enqueue_task, dequeue_task | 入队/出队管理 |
| 选取任务 | pick_task, pick_next_task | 核心调度决策 |
| 任务切换 | put_prev_task, set_next_task | 上下文切换支持 |
| 负载均衡 | balance, find_lock_rq | 多 CPU 负载均衡 |
| 事件处理 | task_tick, task_woken, migrate_task_rq | 各种调度事件 |
6.2 优先级比较
sched_class_above(a, b) 宏通过比较指针地址判断优先级。链接脚本保证高优先级调度类在低优先级之前，因此地址较小的类优先级更高。
7. 关键源码位置
| 组件 | 文件 | 行号 |
|---|---|---|
| struct sched_class | kernel/sched/sched.h | 2500-2661 |
| DEFINE_SCHED_CLASS | kernel/sched/sched.h | 2709-2712 |
| SCHED_DATA | include/asm-generic/vmlinux.lds.h | 153-162 |
| stop_sched_class | kernel/sched/stop_task.c | 99-119 |
| dl_sched_class | kernel/sched/deadline.c | 3406-3437 |
| rt_sched_class | kernel/sched/rt.c | 2581-2611 |
| fair_sched_class | kernel/sched/fair.c | 13951-13980 |
| idle_sched_class | kernel/sched/idle.c | 569-590 |
| __pick_next_task | kernel/sched/core.c | 5909-5964 |
| __setscheduler_class | kernel/sched/core.c | 7254-7266 |