Xen的调度分析 (五) ——关于RTDS调度算法简介

credit算法看的头晕，现在看一下RTDS算法，换换心情。

貌似中文文献为零，如果你是通过搜索引擎检索到了看过不要怪我太菜啊，我只是个机械专业的学生。。。

先把前言部分人话部分看一下吧，天书部分到后面再看：

/*
 * TODO:
 *
 * Migration compensation and resist like credit2 to better use cache;
 * Lock Holder Problem, using yield?
 * Self switch problem: VCPUs of the same domain may preempt each other;
 */
//任务:
//对补偿和抗拒部分进行移植，类似credit2高效利用缓存
//锁的持有者问题，使用yield吗?
//自开关的问题：同一个域的可能会互相抢占VCPU;

/*
 * Design:
 *
 * This scheduler follows the Preemptive Global Earliest Deadline First (EDF)
 * theory in real-time field.
 * At any scheduling point, the VCPU with earlier deadline has higher priority.
 * The scheduler always picks highest priority VCPU to run on a feasible PCPU.
 * A PCPU is feasible if the VCPU can run on this PCPU and (the PCPU is idle or
 * has a lower-priority VCPU running on it.)
 *
//设计思路
//该调度器遵循全局抢占最早时限优先(EDF)理论,用于实时调度领域
//在每次调度中，那些有更早期限的任务将会有更高的优先级
//调度器总是选择一个更高优先级的VCPU运行在可运行的物理CPU上。
//一个可运行的pcpu指的是一个VCPU可以运行在该pcpu上，(包括pcpu处于空闲或有低优先级任务)

 * Each VCPU has a dedicated period and budget.
 * The deadline of a VCPU is at the end of each period;
 * A VCPU has its budget replenished at the beginning of each period;
 * While scheduled, a VCPU burns its budget.
 * The VCPU needs to finish its budget before its deadline in each period;
 * The VCPU discards its unused budget at the end of each period.
 * If a VCPU runs out of budget in a period, it has to wait until next period.
 *
//每一个VCPU都有专属的期限和预算
//一个VCPU的期限是每个周期的结束时间
//一个VCPU拥有的预算在每个周期的开始补充
//若调度，一个VCPU消耗他的预算
//一个VCPU必须在每一个周期内完成他的预算
//一个VCPU在每个周期丢掉未用完的预算
//如果在一个周期内VCPU用光了预算，就得等待下一个周期


 * Each VCPU is implemented as a deferable server.
 * When a VCPU has a task running on it, its budget is continuously burned;
 * When a VCPU has no task but with budget left, its budget is preserved.
 *
 * Queue scheme:
 * A global runqueue and a global depletedqueue for each CPU pool.
 * The runqueue holds all runnable VCPUs with budget, sorted by deadline;
 * The depletedqueue holds all VCPUs without budget, unsorted;
 *
 * Note: cpumask and cpupool is supported.
 */

//每一个VCPU以可延期的服务实现
//当一个VCPU运行任务时，预算被持续的消耗
//当一个VCPU没有任务但是有剩余的预算，该预算被保留

//队列方案
//为每一个cpu池设置一个全局的运行队列和全局的耗尽队列
//运行队列保存所有的可运行的VCPU和预算，以期限排序
//耗尽队列以非排序的方式保存所有预算用完的VCPU

/*
 * Locking:
 * A global system lock is used to protect the RunQ and DepletedQ.
 * The global lock is referenced by schedule_data.schedule_lock
 * from all physical cpus.
 *
 * The lock is already grabbed when calling wake/sleep/schedule/ functions
 * in schedule.c
 *
 * The functions involes RunQ and needs to grab locks are:
 *    vcpu_insert, vcpu_remove, context_saved, __runq_insert
 */

//全局的锁用于保护runq和depletedq
//全局的锁由所有物理CPU在schedule_data.schedule_lock引用
//schedule.c中每次唤醒/睡眠/调度函数运行时，已经上锁了
//包含runq的函数，需要上锁的有VCPU的插入移除、运行队列插入、上下文保存

后面又出现了很多cpumask部分，看来需要看的东西实在是太多了。

因为之前的credit负载平衡也有很多cpumask部分，所以下一篇开始看cpumask部分