烟台网站建设科技公司,宿迁房产网58同城网,点点网 wordpress,wordpress游戏资讯接前一篇文章Linux内核Thermal框架详解十二、Thermal Governor#xff08;2#xff09; 二、具体温控策略
上一篇文章介绍并详细分析了bang_bang governor的源码。本文介绍第2种温控策略#xff1a;fair_share。
2. fair_share
fair_share governor总的策略是频率档位⽐较…接前一篇文章Linux内核Thermal框架详解十二、Thermal Governor2 二、具体温控策略
上一篇文章介绍并详细分析了bang_bang governor的源码。本文介绍第2种温控策略fair_share。
2. fair_share
fair_share governor总的策略是频率档位⽐较多的cooling device优先降频。
fair_share governor的代码在drivers/thermal/gov_fair_share.c中也很简短一共才124行有效代码不到100行。如下所示
#include linux/thermal.h
#include trace/events/thermal.h#include thermal_core.h/*** get_trip_level: - obtains the current trip level for a zone* tz: thermal zone device*/
static int get_trip_level(struct thermal_zone_device *tz)
{int count 0;int trip_temp;enum thermal_trip_type trip_type;if (tz-trips 0 || !tz-ops-get_trip_temp)return 0;for (count 0; count tz-trips; count) {tz-ops-get_trip_temp(tz, count, trip_temp);if (tz-temperature trip_temp)break;}/** count 0 only if temperature is greater than first trip* point, in which case, trip_point count - 1*/if (count 0) {tz-ops-get_trip_type(tz, count - 1, trip_type);trace_thermal_zone_trip(tz, count - 1, trip_type);}return count;
}static long get_target_state(struct thermal_zone_device *tz,struct thermal_cooling_device *cdev, int percentage, int level)
{unsigned long max_state;cdev-ops-get_max_state(cdev, max_state);return (long)(percentage * level * max_state) / (100 * tz-trips);
}/*** fair_share_throttle - throttles devices associated with the given zone* tz: thermal_zone_device* trip: trip point index** Throttling Logic: This uses three parameters to calculate the new* throttle state of the cooling devices associated with the given zone.** Parameters used for Throttling:* P1. max_state: Maximum throttle state exposed by the cooling device.* P2. percentage[i]/100:* How effective the ith device is, in cooling the given zone.* P3. cur_trip_level/max_no_of_trips:* This describes the extent to which the devices should be throttled.* We do not want to throttle too much when we trip a lower temperature,* whereas the throttling is at full swing if we trip critical levels.* (Heavily assumes the trip points are in ascending order)* new_state of cooling device P3 * P2 * P1*/
static int fair_share_throttle(struct thermal_zone_device *tz, int trip)
{struct thermal_instance *instance;int total_weight 0;int total_instance 0;int cur_trip_level get_trip_level(tz);mutex_lock(tz-lock);list_for_each_entry(instance, tz-thermal_instances, tz_node) {if (instance-trip ! trip)continue;total_weight instance-weight;total_instance;}list_for_each_entry(instance, tz-thermal_instances, tz_node) {int percentage;struct thermal_cooling_device *cdev instance-cdev;if (instance-trip ! trip)continue;if (!total_weight)percentage 100 / total_instance;elsepercentage (instance-weight * 100) / total_weight;instance-target get_target_state(tz, cdev, percentage,cur_trip_level);mutex_lock(cdev-lock);__thermal_cdev_update(cdev);mutex_unlock(cdev-lock);}mutex_unlock(tz-lock);return 0;
}static struct thermal_governor thermal_gov_fair_share {.name fair_share,.throttle fair_share_throttle,
};
THERMAL_GOVERNOR_DECLARE(thermal_gov_fair_share);
同样是麻雀虽小五脏俱全。别看代码行数比较少但是背后的机制却并不简单。一段一段来进行分析。
1THERMAL_GOVERNOR_DECLARE相关代码
先来看THERMAL_GOVERNOR_DECLARE。它是一个宏定义在drivers/thermal/thermal_core.h中代码如下
/* Init section thermal table */
extern struct thermal_governor *__governor_thermal_table[];
extern struct thermal_governor *__governor_thermal_table_end[];#define THERMAL_TABLE_ENTRY(table, name) \static typeof(name) *__thermal_table_entry_##name \__used __section(__ #table _thermal_table) name#define THERMAL_GOVERNOR_DECLARE(name) THERMAL_TABLE_ENTRY(governor, name)实际上这段代码在前文Linux内核Thermal框架详解四、Thermal Core3中已经进行了详细分析这里就不再赘述了。不过为了便于理解和加深印象将fair_share governor展开后的代码再次列出
static struct thermal_governor thermal_gov_fair_share {.name fair_share,.throttle fair_share_throttle,
};static struct thermal_governor *__thermal_table_entry_thermal_gov_fair_share \__used __section(__governor_thermal_table) thermal_gov_fair_share
Thermal Governor都是通过THERMAL_GOVERNOR_DECLARE定义到了__governor_thermal_table这段空间内。然后在thermal core初始化时通过调用thermal_register_governors来注册到thermal_governor_list链表中。再之后通过经由“thermal_init-thermal_register_governors- thermal_set_governor”路径和thermal zone device关联上。
2handle_non_critical_trips
struct thermal_governor中有一个成员throttle其是一个函数指针
int (*throttle)(struct thermal_zone_device *tz, int trip);
对于对象thermal_gov_fair_share来说指向了fair_share_throttle函数。在解析fair_share_throttle函数之前有一个问题必须弄清楚这个函数是何时被调用的
是在drivers/thermal/thermal_core.c的handle_non_critical_trips函数中代码如下
static void handle_non_critical_trips(struct thermal_zone_device *tz, int trip)
{tz-governor ? tz-governor-throttle(tz, trip) :def_governor-throttle(tz, trip);
}
那么又是哪里调用的handle_non_critical_trips是在drivers/thermal/thermal_core.c的handle_thermal_trip函数中代码如下
static void handle_thermal_trip(struct thermal_zone_device *tz, int trip)
{enum thermal_trip_type type;int trip_temp, hyst 0;/* Ignore disabled trip points */if (test_bit(trip, tz-trips_disabled))return;tz-ops-get_trip_temp(tz, trip, trip_temp);tz-ops-get_trip_type(tz, trip, type);if (tz-ops-get_trip_hyst)tz-ops-get_trip_hyst(tz, trip, hyst);if (tz-last_temperature ! THERMAL_TEMP_INVALID) {if (tz-last_temperature trip_temp tz-temperature trip_temp)thermal_notify_tz_trip_up(tz-id, trip,tz-temperature);if (tz-last_temperature trip_temp tz-temperature (trip_temp - hyst))thermal_notify_tz_trip_down(tz-id, trip,tz-temperature);}if (type THERMAL_TRIP_CRITICAL || type THERMAL_TRIP_HOT)handle_critical_trips(tz, trip, type);elsehandle_non_critical_trips(tz, trip);/** Alright, we handled this trip successfully.* So, start monitoring again.*/monitor_thermal_zone(tz);
}
对于handle_thermal_trip函数的详细分析有专门的文章章节由于本篇文章专注于fair_share governor故在此不深入展开。
3fair_share_throttle
再贴一下此函数代码
/*** fair_share_throttle - throttles devices associated with the given zone* tz: thermal_zone_device* trip: trip point index** Throttling Logic: This uses three parameters to calculate the new* throttle state of the cooling devices associated with the given zone.** Parameters used for Throttling:* P1. max_state: Maximum throttle state exposed by the cooling device.* P2. percentage[i]/100:* How effective the ith device is, in cooling the given zone.* P3. cur_trip_level/max_no_of_trips:* This describes the extent to which the devices should be throttled.* We do not want to throttle too much when we trip a lower temperature,* whereas the throttling is at full swing if we trip critical levels.* (Heavily assumes the trip points are in ascending order)* new_state of cooling device P3 * P2 * P1*/
static int fair_share_throttle(struct thermal_zone_device *tz, int trip)
{struct thermal_instance *instance;int total_weight 0;int total_instance 0;int cur_trip_level get_trip_level(tz);mutex_lock(tz-lock);list_for_each_entry(instance, tz-thermal_instances, tz_node) {if (instance-trip ! trip)continue;total_weight instance-weight;total_instance;}list_for_each_entry(instance, tz-thermal_instances, tz_node) {int percentage;struct thermal_cooling_device *cdev instance-cdev;if (instance-trip ! trip)continue;if (!total_weight)percentage 100 / total_instance;elsepercentage (instance-weight * 100) / total_weight;instance-target get_target_state(tz, cdev, percentage,cur_trip_level);mutex_lock(cdev-lock);__thermal_cdev_update(cdev);mutex_unlock(cdev-lock);}mutex_unlock(tz-lock);return 0;
}函数注释已经将函数功能说得很清楚了对与给定thermal zone关联的设备进行节流。调节逻辑如下
使用3个参数计算与给定thermal zone相关联的冷却设备的最新throttle state。
用于节流的3个参数注意不是函数的参数
参数1. max_state
冷却设备暴露的最大throttle state。
参数2. percentage[i]/100
第i个设备在冷却给定区域方面的”有效性”。
参数3. cur_trip_level/max_no_of_trips
这个参数描述设备应被节流的限度。当到达较低的温度时不需要节流太多反之如果在临界水平节流就处于全开状态。在很大程度上假设跳闸点按升序排列。
new_state of cooling device P3 * P2 * P1
代码的大致流程如下
1得到指定thermal zone的trip level
通过get_trip_level(tz)得到指定thermal zone的trip level。
get_trip_level函数在同文件drivers/thermal/gov_fair_share.c中实现代码如下
/*** get_trip_level: - obtains the current trip level for a zone* tz: thermal zone device*/
static int get_trip_level(struct thermal_zone_device *tz)
{int count 0;int trip_temp;enum thermal_trip_type trip_type;if (tz-trips 0 || !tz-ops-get_trip_temp)return 0;for (count 0; count tz-trips; count) {tz-ops-get_trip_temp(tz, count, trip_temp);if (tz-temperature trip_temp)break;}/** count 0 only if temperature is greater than first trip* point, in which case, trip_point count - 1*/if (count 0) {tz-ops-get_trip_type(tz, count - 1, trip_type);trace_thermal_zone_trip(tz, count - 1, trip_type);}return count;
}依次遍历各个触发点trips并得到相应触发点的温度。如果给定thermal zone的温度小于某一触发点的温度则跳出循环。 未完待续……
