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sched_domain用于描述调度域：

struct sched_domain {	/* These fields must be setup */	struct sched_domain *parent;	/* top domain must be null terminated */	struct sched_domain *child;	/* bottom domain must be null terminated */	struct sched_group *groups;	/* the balancing groups of the domain */	unsigned long min_interval;	/* Minimum balance interval ms */	unsigned long max_interval;	/* Maximum balance interval ms */	unsigned int busy_factor;	/* less balancing by factor if busy */	unsigned int imbalance_pct;	/* No balance until over watermark */	unsigned int cache_nice_tries;	/* Leave cache hot tasks for # tries */	unsigned int busy_idx;	unsigned int idle_idx;	unsigned int newidle_idx;	unsigned int wake_idx;	unsigned int forkexec_idx;	unsigned int smt_gain;	int nohz_idle;			/* NOHZ IDLE status */	int flags;			/* See SD_* */	int level;	/* Runtime fields. */	unsigned long last_balance;	/* init to jiffies. units in jiffies */	unsigned int balance_interval;	/* initialise to 1. units in ms. */	unsigned int nr_balance_failed; /* initialise to 0 */	/* idle_balance() stats */	u64 max_newidle_lb_cost;	unsigned long next_decay_max_lb_cost;	u64 avg_scan_cost;		/* select_idle_sibling */#ifdef CONFIG_SCHEDSTATS	/* load_balance() stats */	unsigned int lb_count[CPU_MAX_IDLE_TYPES];	unsigned int lb_failed[CPU_MAX_IDLE_TYPES];	unsigned int lb_balanced[CPU_MAX_IDLE_TYPES];	unsigned int lb_imbalance[CPU_MAX_IDLE_TYPES];	unsigned int lb_gained[CPU_MAX_IDLE_TYPES];	unsigned int lb_hot_gained[CPU_MAX_IDLE_TYPES];	unsigned int lb_nobusyg[CPU_MAX_IDLE_TYPES];	unsigned int lb_nobusyq[CPU_MAX_IDLE_TYPES];	/* Active load balancing */	unsigned int alb_count;	unsigned int alb_failed;	unsigned int alb_pushed;	/* SD_BALANCE_EXEC stats */	unsigned int sbe_count;	unsigned int sbe_balanced;	unsigned int sbe_pushed;	/* SD_BALANCE_FORK stats */	unsigned int sbf_count;	unsigned int sbf_balanced;	unsigned int sbf_pushed;	/* try_to_wake_up() stats */	unsigned int ttwu_wake_remote;	unsigned int ttwu_move_affine;	unsigned int ttwu_move_balance;#endif#ifdef CONFIG_SCHED_DEBUG	char *name;#endif	union {		void *private;		/* used during construction */		struct rcu_head rcu;	/* used during destruction */	};	struct sched_domain_shared *shared;	unsigned int span_weight;	/*	 * Span of all CPUs in this domain.	 *	 * NOTE: this field is variable length. (Allocated dynamically	 * by attaching extra space to the end of the structure,	 * depending on how many CPUs the kernel has booted up with)	 */	unsigned long span[0];};

调度域静态定义，其跟CPU拓扑结构密切相关。

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