boosted_task_util实际上包含两个部分，当前task的util加上margin值，margin就是将util的值给他扩大或者缩小一定的倍数

boosted_task_util

static inline unsigned long boosted_task_util(struct task_struct *task) { unsigned long util = task_util_est(task);//这里我们假设walt机制是open的 long margin = schedtune_task_margin(task);//margin就是sign除以100 trace_sched_boost_task(task, util, margin);//添加到内核trace log里面 return util + margin; }

task_util & task_util_est

task util = demand *1024 / window_size  ---其中demand为WALT机制中sum_history数组得到的max(latest值，平均值)，window_size则是WALT机制中window的大小（默认为20ms）

 

未开启boost　　　 = (delta / window_size) * (cur_freq / max_freq) * cpu_max_capacity ---delta是task在一个window中运行的真实时间；cur_freq为cpu当前频率；max_freq为cpu最大频率；

 

开启boost  task util也会进行变化。公式如下：

boosted task util = task_util +（1024 - task_util）* boost_percent ---boost_percent是schedtune中配置的boost百分比

static inline unsigned long task_util(struct task_struct *p) { #ifdef CONFIG_SCHED_WALT if (likely(!walt_disabled && sysctl_sched_use_walt_task_util)) return (p->ravg.demand / (walt_ravg_window >> SCHED_CAPACITY_SHIFT)); #endif return READ_ONCE(p->se.avg.util_avg); }

Task­­ utilization 的估算也是依赖walt进行窗口的统计

static inline unsigned long task_util_est(struct task_struct *p) { #ifdef CONFIG_SCHED_WALT if (likely(!walt_disabled && sysctl_sched_use_walt_task_util)) return (p->ravg.demand / (walt_ravg_window >> SCHED_CAPACITY_SHIFT)); #endif return max(task_util(p), _task_util_est(p)); }

_task_util_est

task util是用来表示一个task大小，它会占用cpu多少算力，或者说是给cpu造成多少负载的体现

static inline unsigned long _task_util_est(struct task_struct *p) { struct util_est ue = READ_ONCE(p->se.avg.util_est);//这里应该是读取一次一个数据结构的宏 return max(ue.ewma, ue.enqueued); }

关于struct util_est，可以看https://blog.csdn.net/feifei_csdn/article/details/107106149

struct util_est {

    unsigned int            enqueued;入队列时估算的task的效力

unsigned int            ewma;指数加权动态的平均task的效力

schedtune_task_margin

static inline long schedtune_task_margin(struct task_struct *task) { int boost = schedtune_task_boost(task);//返回的应该是我们设置的值-100到100 unsigned long util; long margin; if (boost == 0) return 0; util = task_util_est(task); margin = schedtune_margin(util, boost);//对util进行一定的缩放 return margin; }

schedtune_margin

对uti进行成比例的缩放

unsigned int spc_threshold = 100; struct reciprocal_value schedtune_spc_rdiv; static long schedtune_margin(unsigned long signal, long boost) { long long margin = 0; /* * Signal proportional(成比例的) compensation(补偿)(SPC) * * The Boost (B) value is used to compute a Margin (M) which is * proportional to the complement of the original Signal (S): * M = B * (SCHED_CAPACITY_SCALE - S) * The obtained M could be used by the caller to "boost" S. */ if (boost >= 0) { if (signal < spc_threshold) margin = signal * boost; else { margin = SCHED_CAPACITY_SCALE - signal; margin *= boost; } } else margin = -signal * boost; margin = reciprocal_divide(margin, schedtune_spc_rdiv); // reciprocal_divide是计算A/B的优化函数 if (boost < 0) margin *= -1; return margin; }