Linux 编程之经典多级时间轮定时器（上）
上图是5个时间轮级联的效果图。中间的大轮是工作轮，只有在它上的任务才会被执行；其他轮上的任务时间到后迁移到下一级轮上，他们最终都会迁移到工作轮上而被调度执行。
多级时间轮的原理也容易理解：就拿时钟做说明，秒针转动一圈分针转动一格；分针转动一圈时针转动一格；同理时间轮也是如此：当低级轮转动一圈时，高一级轮转动一格，同时会将高一级轮上的任务重新分配到低级轮上。从而实现了多级轮级联的效果。
1.1 多级时间轮对象
多级时间轮应该至少包括以下内容：
每一级时间轮对象轮子上指针的位置关于轮子上指针的位置有一个比较巧妙的办法：那就是位运算。比如定义一个无符号整型的数：
通过获取当前的系统时间便可以通过位操作转换为时间轮上的时间，通过与实际时间轮上的时间作比较，从而确定时间轮要前进调度的时间，进而操作对应时间轮槽位对应的任务。
为什么至少需要这两个成员呢？
定义多级时间轮，首先需要明确的便是级联的层数，也就是说需要确定有几个时间轮。轮子上指针位置，就是当前时间轮运行到的位置，它与真实时间的差便是后续时间轮需要调度执行，它们的差值是时间轮运作起来的驱动力。多级时间轮对象的定义
//实现5级时间轮 范围为0~ (2^8 * 2^6 * 2^6 * 2^6 *2^6)=2^32struct tvec_base{ unsigned long current_index; pthread_t thincrejiffies; pthread_t threadid; struct tvec_root tv1; /*第一个轮*/ struct tvec tv2; /*第二个轮*/ struct tvec tv3; /*第三个轮*/ struct tvec tv4; /*第四个轮*/ struct tvec tv5; /*第五个轮*/};1.2 时间轮对象
我们知道每一个轮子实际上都是一个哈希表，上面我们只是实例化了五个轮子的对象，但是五个轮子具体包含什么，有几个槽位等等没有明确(即struct tvec和struct tvec_root)。
#define tvn_bits 6#define tvr_bits 8#define tvn_size (1next = (ptr); (ptr)->prev = (ptr); \\} while (0)static inline void__list_add(struct list_head *entry, struct list_head *prev, struct list_head *next){ next->prev = entry; entry->next = next; entry->prev = prev; prev->next = entry;}/** * insert a new element after the given list head. the new element does not * need to be initialised as empty list. * the list changes from: * head → some element → ... * to * head → new element → older element → ... * * example: * struct foo *newfoo = malloc(...); * list_add(&newfoo->entry, &bar->list_of_foos); * * @param entry the new element to prepend to the list. * @param head the existing list. */static inline voidlist_add(struct list_head *entry, struct list_head *head){ __list_add(entry, head, head->next);}/** * append a new element to the end of the list given with this list head. * * the list changes from: * head → some element → ... → lastelement * to * head → some element → ... → lastelement → new element * * example: * struct foo *newfoo = malloc(...); * list_add_tail(&newfoo->entry, &bar->list_of_foos); * * @param entry the new element to prepend to the list. * @param head the existing list. */static inline voidlist_add_tail(struct list_head *entry, struct list_head *head){ __list_add(entry, head->prev, head);}static inline void__list_del(struct list_head *prev, struct list_head *next){ next->prev = prev; prev->next = next;}/** * remove the element from the list it is in. using this function will reset * the pointers to/from this element so it is removed from the list. it does * not free the element itself or manipulate it otherwise. * * using list_del on a pure list head (like in the example at the top of * this file) will not remove the first element from * the list but rather reset the list as empty list. * * example: * list_del(&foo->entry); * * @param entry the element to remove. */static inline voidlist_del(struct list_head *entry){ __list_del(entry->prev, entry->next);}static inline voidlist_del_init(struct list_head *entry){ __list_del(entry->prev, entry->next); init_list_head(entry);}static inline void list_move_tail(struct list_head *list, struct list_head *head){ __list_del(list->prev, list->next); list_add_tail(list, head);}/** * check if the list is empty. * * example: * list_empty(&bar->list_of_foos); * * @return true if the list contains one or more elements or false otherwise. */static inline intlist_empty(struct list_head *head){ return head->next == head;}/** * list_replace - replace old entry by new one * @old : the element to be replaced * @new : the new element to insert * * if @old was empty, it will be overwritten. */static inline void list_replace(struct list_head *old, struct list_head *new){ new->next = old->next; new->next->prev = new; new->prev = old->prev; new->prev->next = new;}/** * retrieve the first list entry for the given list pointer. * * example: * struct foo *first; * first = list_first_entry(&bar->list_of_foos, struct foo, list_of_foos); * * @param ptr the list head * @param type data type of the list element to retrieve * @param member member name of the struct list_head field in the list element. * @return a pointer to the first list element. */#define list_first_entry(ptr, type, member) \\ list_entry((ptr)->next, type, member)static inline void list_replace_init(struct list_head *old, struct list_head *new){ list_replace(old, new); init_list_head(old);}/** * list_entry - get the struct for this entry * @ptr: the &struct list_head pointer. * @type: the type of the struct this is embedded in. * @member: the name of the list_struct within the struct. */#define list_entry(ptr, type, member) \\ ((type *)((char *)(ptr)-(unsigned long)(&((type *)0)->member)))/** * list_for_each - iterate over elements in a list * @pos: the &struct list_head to use as a loop counter. * @head: the head for your list. */#define list_for_each(pos, head) \\ for (pos = (head)->next; pos != (head); pos = pos->next)/** * list_for_each_safe - iterate over elements in a list, but don't dereference * pos after the body is done (in case it is freed) * @pos: the &struct list_head to use as a loop counter. * @pnext: the &struct list_head to use as a pointer to the next item. * @head: the head for your list (not included in iteration). */#define list_for_each_safe(pos, pnext, head) \\ for (pos = (head)->next, pnext = pos->next; pos != (head); \\ pos = pnext, pnext = pos->next)#ifdef __cplusplus}#endif#endif /* _blkid_list_h */这里面一般会用到一个重要实现：container_of, 它的原理这里不叙述
2.2 调试信息头文件: log.h这个头文件实际上不是必须的，我只是用它来添加调试信息(代码中的errlog(), log()都是log.h中的宏函数)。它的效果是给打印的信息加上颜色，效果如下：
log.h的代码如下：
#ifndef _log_h_#define _log_h_#include #define col(x) \\033[; #x m#define red col(31)#define green col(32)#define yellow col(33)#define blue col(34)#define magenta col(35)#define cyan col(36)#define white col(0)#define gray \\033[0m#define errlog(fmt, arg...) do{ \\ printf(red[#error: toeny sun:gray yellow %s:%d]:gray white fmt gray, __func__, __line__, ##arg);\\}while(0)#define log(fmt, arg...) do{ \\ printf(white[#debug: toeny sun: gray yellow%s:%d]:gray white fmt gray, __func__, __line__, ##arg);\\}while(0)#endif
哪些因素影响着3D打印的成型速度?
高压变频器在钢铁烧结厂高压同步电机上的应用
多串口通信服务器
高速转换器中的PCB布局布线规则
设备控制器基本功能
Linux 编程之经典多级时间轮定时器（上）
国家标准《氢系统安全的基本要求》4月1日起实施
【世说芯品】赋能绿色未来 | 芯讯通助力能耗大户书写“绿色答卷”
Lava Be U在印度正式发布 采用八核SC9863A处理器
CSA发表针对固定式电动工具修订标准
达实智能大厦开放性平台助力智慧建筑园区数字化转型升级
格力“色界”手机-让世界知道格力不只做空调,更多的还有手机行业！
瀚天天成IPO获受理，拟于上交所科创板上市
安森美开设欧洲电动汽车系统应用实验室
华润微:IPM模块已经处于稳定上量的过程中
受疫情影响 冰箱空调洗衣机必须得抗住短时间的压力
养羊场智能养殖方案
华为微博更名并宣布鸿蒙操作系统及全场景新品发布会将在6月2日举行
重磅！传感器圈30大超亿元融资案
如何防止科学狂人和基因编辑技术再次突破底线
多级时间轮的原理也容易理解：就拿时钟做说明，秒针转动一圈分针转动一格；分针转动一圈时针转动一格；同理时间轮也是如此：当低级轮转动一圈时，高一级轮转动一格，同时会将高一级轮上的任务重新分配到低级轮上。从而实现了多级轮级联的效果。
1.1 多级时间轮对象
多级时间轮应该至少包括以下内容：
每一级时间轮对象轮子上指针的位置关于轮子上指针的位置有一个比较巧妙的办法：那就是位运算。比如定义一个无符号整型的数：
通过获取当前的系统时间便可以通过位操作转换为时间轮上的时间，通过与实际时间轮上的时间作比较，从而确定时间轮要前进调度的时间，进而操作对应时间轮槽位对应的任务。
为什么至少需要这两个成员呢？
定义多级时间轮，首先需要明确的便是级联的层数，也就是说需要确定有几个时间轮。轮子上指针位置，就是当前时间轮运行到的位置，它与真实时间的差便是后续时间轮需要调度执行，它们的差值是时间轮运作起来的驱动力。多级时间轮对象的定义
//实现5级时间轮 范围为0~ (2^8 * 2^6 * 2^6 * 2^6 *2^6)=2^32struct tvec_base{ unsigned long current_index; pthread_t thincrejiffies; pthread_t threadid; struct tvec_root tv1; /*第一个轮*/ struct tvec tv2; /*第二个轮*/ struct tvec tv3; /*第三个轮*/ struct tvec tv4; /*第四个轮*/ struct tvec tv5; /*第五个轮*/};1.2 时间轮对象
我们知道每一个轮子实际上都是一个哈希表，上面我们只是实例化了五个轮子的对象，但是五个轮子具体包含什么，有几个槽位等等没有明确(即struct tvec和struct tvec_root)。
#define tvn_bits 6#define tvr_bits 8#define tvn_size (1next = (ptr); (ptr)->prev = (ptr); \\} while (0)static inline void__list_add(struct list_head *entry, struct list_head *prev, struct list_head *next){ next->prev = entry; entry->next = next; entry->prev = prev; prev->next = entry;}/** * insert a new element after the given list head. the new element does not * need to be initialised as empty list. * the list changes from: * head → some element → ... * to * head → new element → older element → ... * * example: * struct foo *newfoo = malloc(...); * list_add(&newfoo->entry, &bar->list_of_foos); * * @param entry the new element to prepend to the list. * @param head the existing list. */static inline voidlist_add(struct list_head *entry, struct list_head *head){ __list_add(entry, head, head->next);}/** * append a new element to the end of the list given with this list head. * * the list changes from: * head → some element → ... → lastelement * to * head → some element → ... → lastelement → new element * * example: * struct foo *newfoo = malloc(...); * list_add_tail(&newfoo->entry, &bar->list_of_foos); * * @param entry the new element to prepend to the list. * @param head the existing list. */static inline voidlist_add_tail(struct list_head *entry, struct list_head *head){ __list_add(entry, head->prev, head);}static inline void__list_del(struct list_head *prev, struct list_head *next){ next->prev = prev; prev->next = next;}/** * remove the element from the list it is in. using this function will reset * the pointers to/from this element so it is removed from the list. it does * not free the element itself or manipulate it otherwise. * * using list_del on a pure list head (like in the example at the top of * this file) will not remove the first element from * the list but rather reset the list as empty list. * * example: * list_del(&foo->entry); * * @param entry the element to remove. */static inline voidlist_del(struct list_head *entry){ __list_del(entry->prev, entry->next);}static inline voidlist_del_init(struct list_head *entry){ __list_del(entry->prev, entry->next); init_list_head(entry);}static inline void list_move_tail(struct list_head *list, struct list_head *head){ __list_del(list->prev, list->next); list_add_tail(list, head);}/** * check if the list is empty. * * example: * list_empty(&bar->list_of_foos); * * @return true if the list contains one or more elements or false otherwise. */static inline intlist_empty(struct list_head *head){ return head->next == head;}/** * list_replace - replace old entry by new one * @old : the element to be replaced * @new : the new element to insert * * if @old was empty, it will be overwritten. */static inline void list_replace(struct list_head *old, struct list_head *new){ new->next = old->next; new->next->prev = new; new->prev = old->prev; new->prev->next = new;}/** * retrieve the first list entry for the given list pointer. * * example: * struct foo *first; * first = list_first_entry(&bar->list_of_foos, struct foo, list_of_foos); * * @param ptr the list head * @param type data type of the list element to retrieve * @param member member name of the struct list_head field in the list element. * @return a pointer to the first list element. */#define list_first_entry(ptr, type, member) \\ list_entry((ptr)->next, type, member)static inline void list_replace_init(struct list_head *old, struct list_head *new){ list_replace(old, new); init_list_head(old);}/** * list_entry - get the struct for this entry * @ptr: the &struct list_head pointer. * @type: the type of the struct this is embedded in. * @member: the name of the list_struct within the struct. */#define list_entry(ptr, type, member) \\ ((type *)((char *)(ptr)-(unsigned long)(&((type *)0)->member)))/** * list_for_each - iterate over elements in a list * @pos: the &struct list_head to use as a loop counter. * @head: the head for your list. */#define list_for_each(pos, head) \\ for (pos = (head)->next; pos != (head); pos = pos->next)/** * list_for_each_safe - iterate over elements in a list, but don't dereference * pos after the body is done (in case it is freed) * @pos: the &struct list_head to use as a loop counter. * @pnext: the &struct list_head to use as a pointer to the next item. * @head: the head for your list (not included in iteration). */#define list_for_each_safe(pos, pnext, head) \\ for (pos = (head)->next, pnext = pos->next; pos != (head); \\ pos = pnext, pnext = pos->next)#ifdef __cplusplus}#endif#endif /* _blkid_list_h */这里面一般会用到一个重要实现：container_of, 它的原理这里不叙述
2.2 调试信息头文件: log.h这个头文件实际上不是必须的，我只是用它来添加调试信息(代码中的errlog(), log()都是log.h中的宏函数)。它的效果是给打印的信息加上颜色，效果如下：
log.h的代码如下：
#ifndef _log_h_#define _log_h_#include #define col(x) \\033[; #x m#define red col(31)#define green col(32)#define yellow col(33)#define blue col(34)#define magenta col(35)#define cyan col(36)#define white col(0)#define gray \\033[0m#define errlog(fmt, arg...) do{ \\ printf(red[#error: toeny sun:gray yellow %s:%d]:gray white fmt gray, __func__, __line__, ##arg);\\}while(0)#define log(fmt, arg...) do{ \\ printf(white[#debug: toeny sun: gray yellow%s:%d]:gray white fmt gray, __func__, __line__, ##arg);\\}while(0)#endif
哪些因素影响着3D打印的成型速度?
高压变频器在钢铁烧结厂高压同步电机上的应用
多串口通信服务器
高速转换器中的PCB布局布线规则
设备控制器基本功能
Linux 编程之经典多级时间轮定时器（上）
国家标准《氢系统安全的基本要求》4月1日起实施
【世说芯品】赋能绿色未来 | 芯讯通助力能耗大户书写“绿色答卷”
Lava Be U在印度正式发布 采用八核SC9863A处理器
CSA发表针对固定式电动工具修订标准
达实智能大厦开放性平台助力智慧建筑园区数字化转型升级
格力“色界”手机-让世界知道格力不只做空调,更多的还有手机行业！
瀚天天成IPO获受理，拟于上交所科创板上市
安森美开设欧洲电动汽车系统应用实验室
华润微:IPM模块已经处于稳定上量的过程中
受疫情影响 冰箱空调洗衣机必须得抗住短时间的压力
养羊场智能养殖方案
华为微博更名并宣布鸿蒙操作系统及全场景新品发布会将在6月2日举行
重磅！传感器圈30大超亿元融资案
如何防止科学狂人和基因编辑技术再次突破底线