Linux ｜负载均衡理解之调度了解

负载均衡

系统中存在的负载有：中断，异常，软中断，系统调用，进程等。

每个处理器各自设置一个调度队列，从而可能出现有的处理器的就绪队列进程很多而另一个处理器上的就绪队列任务很少的现象。

处理器层次结构

调度域分层组织，每个调度域可以包括一个或多个子调度域
调度域指的是一组具有相同属性和调度策略的处理器集合，任务可以在它们内部按某种策略调度迁移。
每个调度域内部可以有一个或多个调度组（Scheduling Groups）
调度域根据Hyper-threading, Multi-core, SMP, Numa architechures 等系统结构划分不同的级别。

CPU负载

内核在每一个运行队列结构中为当前CPU维护一个静态权重load(load_weight), 其值为此次运行队列中的每一个任务权重task_struct->se->load的总和，

/Users/heidsoft/Downloads/research/linux-5.15.4/kernel/sched/fair.c

代码语言：javascript复制

/*
 * sd_lb_stats - Structure to store the statistics of a sched_domain
 *     during load balancing.
 */
struct sd_lb_stats {
  struct sched_group *busiest;  /* Busiest group in this sd */
  struct sched_group *local;  /* Local group in this sd */
  unsigned long total_load;  /* Total load of all groups in sd */
  unsigned long total_capacity;  /* Total capacity of all groups in sd */
  unsigned long avg_load;  /* Average load across all groups in sd */
  unsigned int prefer_sibling; /* tasks should go to sibling first */

  struct sg_lb_stats busiest_stat;/* Statistics of the busiest group */
  struct sg_lb_stats local_stat;  /* Statistics of the local group */
};

代码语言：javascript复制

/*
 * sg_lb_stats - stats of a sched_group required for load_balancing
 */
struct sg_lb_stats {
  unsigned long avg_load; /*Avg load across the CPUs of the group */
  unsigned long group_load; /* Total load over the CPUs of the group */
  unsigned long group_capacity;
  unsigned long group_util; /* Total utilization over the CPUs of the group */
  unsigned long group_runnable; /* Total runnable time over the CPUs of the group */
  unsigned int sum_nr_running; /* Nr of tasks running in the group */
  unsigned int sum_h_nr_running; /* Nr of CFS tasks running in the group */
  unsigned int idle_cpus;
  unsigned int group_weight;
  enum group_type group_type;
  unsigned int group_asym_packing; /* Tasks should be moved to preferred CPU */
  unsigned long group_misfit_task_load; /* A CPU has a task too big for its capacity */
#ifdef CONFIG_NUMA_BALANCING
  unsigned int nr_numa_running;
  unsigned int nr_preferred_running;
#endif
};

Linux System Load
负载均衡情景分析
https://docs.kernel.org/driver-api/basics.html

linux kernel 负载均衡 load scheduling

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Linux ｜ 负载均衡理解之调度了解

Linux ｜负载均衡理解之调度了解