怎么用C语言实现经典多级时间轮定时器

本篇内容介绍了"怎么用C语言实现经典多级时间轮定时器"的有关知识，在实际案例的操作过程中，不少人都会遇到这样的困境，接下来就让小编带领大家学习一下如何处理这些情况吧！希望大家仔细阅读，能够学有所成！

多级时间轮实现框架

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 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*/};

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              (1<
此外，每一个时间轮都是哈希表，因此它的类型应该至少包含两个指针域来实现双向链表的功能。这里我们为了方便使用通用的struct list_head的双向链表结构。
3 定时任务对象
定时器的主要工作是为了在未来的特定时间完成某项任务，而这个任务经常包含以下内容：
任务的处理逻辑(回调函数)
任务的参数
双向链表节点
到时时间
定时任务对象的定义
typedef void (*timeouthandle)(unsigned long ); struct timer_list{    struct list_head entry;          //将时间连接成链表    unsigned long expires;           //超时时间    void (*function)(unsigned long); //超时后的处理函数    unsigned long data;              //处理函数的参数    struct tvec_base *base;          //指向时间轮};
在时间轮上的效果图：
4 双向链表
在时间轮上我们采用双向链表的数据类型。采用双向链表的除了操作上比单链表复杂，多占一个指针域外没有其他不可接收的问题。而多占一个指针域在今天大内存的时代明显不是什么问题。至于双向链表操作的复杂性，我们可以通过使用通用的struct list结构来解决，因为双向链表有众多的标准操作函数，我们可以通过直接引用list.h头文件来使用他们提供的接口。
struct list可以说是一个万能的双向链表操作框架，我们只需要在自定义的结构中定义一个struct list对象即可使用它的标准操作接口。同时它还提供了一个类似container_of的接口，在应用层一般叫做list_entry，因此我们可以很方便的通过struct list成员找到自定义的结构体的起始地址。
关于应用层的log.h, 我将在下面的代码中附上该文件。如果需要内核层的实现，可以直接从linux源码中获取。
5 联结方式
多级时间轮效果图：
多级时间轮C语言实现
1 双向链表头文件: list.h
提到双向链表，很多的源码工程中都会实现一系列的统一的双向链表操作函数。它们为双向链表封装了统计的接口，使用者只需要在自定义的结构中添加一个struct list_head结构，然后调用它们提供的接口，便可以完成双向链表的所有操作。这些操作一般都在list.h的头文件中实现。Linux源码中也有实现（内核态的实现）。他们实现的方式基本完全一样，只是实现的接口数量和功能上稍有差别。可以说这个==list.h文件是学习操作双向链表的不二选择==，它几乎实现了所有的操作：增、删、改、查、遍历、替换、清空等等。这里我拼凑了一个源码中的log.h函数，终于凑够了多级时间轮中使用到的接口(原来的博主没有提供list.h文件，只能自己去东拼西凑)。
#if !defined(_BLKID_LIST_H) && !defined(LIST_HEAD)#define _BLKID_LIST_H#ifdef __cplusplus extern "C" {#endif/* * Simple doubly linked list implementation. * * Some of the internal functions ("__xxx") are useful when * manipulating whole lists rather than single entries, as * sometimes we already know the next/prev entries and we can * generate better code by using them directly rather than * using the generic single-entry routines. */struct list_head {        struct list_head *next, *prev;};#define LIST_HEAD_INIT(name) { &(name), &(name) }#define LIST_HEAD(name)         struct list_head name = LIST_HEAD_INIT(name)#define INIT_LIST_HEAD(ptr) do {         (ptr)->next = (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==, 它的原理如果不清楚的话，可以阅读另一篇专门介绍该函数的博文：container of()函数简介
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)  "33[;" #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    "33[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
3 时间轮代码: timewheel.c
/* *毫秒定时器  采用多级时间轮方式  借鉴linux内核中的实现 *支持的范围为1 ~  2^32 毫秒(大约有49天) *若设置的定时器超过最大值 则按最大值设置定时器 **/#include #include #include #include #include #include #include "list.h"#include "log.h" #define TVN_BITS              6#define TVR_BITS              8#define TVN_SIZE              (1<current_index >> (TVR_BITS + (N) * TVN_BITS)) & TVN_MASK) typedef void (*timeouthandle)(unsigned long );  struct timer_list{    struct list_head entry;          //将时间连接成链表    unsigned long expires;           //超时时间    void (*function)(unsigned long); //超时后的处理函数    unsigned long data;              //处理函数的参数    struct tvec_base *base;          //指向时间轮}; struct tvec {    struct list_head vec[TVN_SIZE];}; struct tvec_root{    struct list_head vec[TVR_SIZE];}; //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*/}; static void internal_add_timer(struct tvec_base *base, struct timer_list *timer){    struct list_head *vec;    unsigned long expires = timer->expires;      unsigned long idx = expires - base->current_index;#if 1     if( (signed long)idx < 0 ) /*这里是没有办法区分出是过时还是超长定时的吧?*/    {        vec = base->tv1.vec + (base->current_index & TVR_MASK);/*放到第一个轮的当前槽*/    }        else if ( idx < TVR_SIZE ) /*第一个轮*/    {        int i = expires & TVR_MASK;        vec = base->tv1.vec + i;    }    else if( idx < 1 << (TVR_BITS + TVN_BITS) )/*第二个轮*/    {        int i = (expires >> TVR_BITS) & TVN_MASK;        vec = base->tv2.vec + i;    }    else if( idx < 1 << (TVR_BITS + 2 * TVN_BITS) )/*第三个轮*/    {        int i = (expires >> (TVR_BITS + TVN_BITS)) & TVN_MASK;        vec = base->tv3.vec + i;    }    else if( idx < 1 << (TVR_BITS + 3 * TVN_BITS) )/*第四个轮*/    {        int i = (expires >> (TVR_BITS + 2 * TVN_BITS)) & TVN_MASK;        vec = base->tv4.vec + i;    }    else                                                                                     /*第五个轮*/    {        int i;        if (idx > 0xffffffffUL)         {            idx = 0xffffffffUL;            expires = idx + base->current_index;        }        i = (expires >> (TVR_BITS + 3 * TVN_BITS)) & TVN_MASK;        vec = base->tv5.vec + i;    }#else        /*上面可以优化吧*/;#endif     list_add_tail(&timer->entry, vec);} static inline void detach_timer(struct timer_list *timer){    struct list_head *entry = &timer->entry;    __list_del(entry->prev, entry->next);    entry->next = NULL;    entry->prev = NULL;} static int __mod_timer(struct timer_list *timer, unsigned long expires){            if(NULL != timer->entry.next)        detach_timer(timer);            internal_add_timer(timer->base, timer);      return 0;} //修改定时器的超时时间外部接口int mod_timer(void *ptimer, unsigned long expires){    struct timer_list *timer  = (struct timer_list *)ptimer;    struct tvec_base *base;                 base = timer->base;    if(NULL == base)        return -1;        expires = expires + base->current_index;        if(timer->entry.next != NULL  && timer->expires == expires)        return 0;     if( NULL == timer->function )    {        errlog("timer"s timeout function is null");        return -1;    }                timer->expires = expires;    return __mod_timer(timer,expires);} //添加一个定时器static void __ti_add_timer(struct timer_list *timer){    if( NULL != timer->entry.next )    {        errlog("timer is already exist");        return;    }     mod_timer(timer, timer->expires);            } /*添加一个定时器  外部接口 *返回定时器 */void* ti_add_timer(void *ptimewheel, unsigned long expires,timeouthandle phandle, unsigned long arg){    struct timer_list  *ptimer;     ptimer = (struct timer_list *)malloc( sizeof(struct timer_list) );    if(NULL == ptimer)        return NULL;     bzero( ptimer,sizeof(struct timer_list) );            ptimer->entry.next = NULL;    ptimer->base = (struct tvec_base *)ptimewheel;     ptimer->expires = expires;    ptimer->function  = phandle;    ptimer->data = arg;     __ti_add_timer(ptimer);     return ptimer;} /* *删除一个定时器  外部接口 * * */void ti_del_timer(void *p){    struct timer_list *ptimer =(struct timer_list*)p;     if(NULL == ptimer)        return;     if(NULL != ptimer->entry.next)        detach_timer(ptimer);        free(ptimer);}/*时间轮级联*/ static int cascade(struct tvec_base *base, struct tvec *tv, int index){    struct list_head *pos,*tmp;    struct timer_list *timer;    struct list_head tv_list;            /*将tv[index]槽位上的所有任务转移给tv_list,然后清空tv[index]*/    list_replace_init(tv->vec + index, &tv_list);/*用tv_list替换tv->vec + index*/     list_for_each_safe(pos, tmp, &tv_list)/*遍历tv_list双向链表，将任务重新添加到时间轮*/    {        timer = list_entry(pos,struct timer_list,entry);/*struct timer_list中成员entry的地址是pos, 获取struct timer_list的首地址*/        internal_add_timer(base, timer);    }     return index;} static void *deal_function_timeout(void *base){    struct timer_list *timer;    int ret;    struct timeval tv;    struct tvec_base *ba = (struct tvec_base *)base;        for(;;)    {        gettimeofday(&tv, NULL);          while( ba->current_index <= (tv.tv_sec*1000 + tv.tv_usec/1000) )/*单位：ms*/        {                    struct list_head work_list;           int index = ba->current_index & TVR_MASK;/*获取第一个轮上的指针位置*/           struct list_head *head = &work_list;                   /*指针指向0槽时，级联轮需要更新任务列表*/           if(!index && (!cascade(ba, &ba->tv2, INDEX(0))) &&( !cascade(ba, &ba->tv3, INDEX(1))) && (!cascade(ba, &ba->tv4, INDEX(2))) )               cascade(ba, &ba->tv5, INDEX(3));                       ba->current_index ++;            list_replace_init(ba->tv1.vec + index, &work_list);            while(!list_empty(head))            {                void (*fn)(unsigned long);                unsigned long data;                timer = list_first_entry(head, struct timer_list, entry);                fn = timer->function;                data = timer->data;                detach_timer(timer);                (*fn)(data);              }        }    }} static void init_tvr_list(struct tvec_root * tvr){    int i;     for( i = 0; ivec[i]);}  static void init_tvn_list(struct tvec * tvn){    int i;     for( i = 0; ivec[i]);} //创建时间轮  外部接口void *ti_timewheel_create(void ){    struct tvec_base *base;    int ret = 0;    struct timeval tv;     base = (struct tvec_base *) malloc( sizeof(struct tvec_base) );    if( NULL==base )        return NULL;        bzero( base,sizeof(struct tvec_base) );            init_tvr_list(&base->tv1);    init_tvn_list(&base->tv2);    init_tvn_list(&base->tv3);    init_tvn_list(&base->tv4);    init_tvn_list(&base->tv5);        gettimeofday(&tv, NULL);    base->current_index = tv.tv_sec*1000 + tv.tv_usec/1000;/*当前时间毫秒数*/     if( 0 != pthread_create(&base->threadID,NULL,deal_function_timeout,base) )    {        free(base);        return NULL;    }        return base;} static void ti_release_tvr(struct tvec_root *pvr){    int i;    struct list_head *pos,*tmp;    struct timer_list *pen;     for(i = 0; i < TVR_SIZE; i++)    {        list_for_each_safe(pos,tmp,&pvr->vec[i])        {            pen = list_entry(pos,struct timer_list, entry);            list_del(pos);            free(pen);        }    }} static void ti_release_tvn(struct tvec *pvn){    int i;    struct list_head *pos,*tmp;    struct timer_list *pen;     for(i = 0; i < TVN_SIZE; i++)    {        list_for_each_safe(pos,tmp,&pvn->vec[i])        {            pen = list_entry(pos,struct timer_list, entry);            list_del(pos);            free(pen);        }    }}  /* *释放时间轮 外部接口 * */void ti_timewheel_release(void * pwheel){      struct tvec_base *base = (struct tvec_base *)pwheel;        if(NULL == base)        return;     ti_release_tvr(&base->tv1);    ti_release_tvn(&base->tv2);    ti_release_tvn(&base->tv3);    ti_release_tvn(&base->tv4);    ti_release_tvn(&base->tv5);     free(pwheel);} /************demo****************/struct request_para{    void *timer;    int val;}; void mytimer(unsigned long arg){    struct request_para *para = (struct request_para *)arg;     log("%d",para->val);    mod_timer(para->timer,3000);  //进行再次启动定时器         sleep(10);/*定时器依然被阻塞*/     //定时器资源的释放是在这里完成的    //ti_del_timer(para->timer);} int main(int argc,char *argv[]){    void *pwheel = NULL;    void *timer  = NULL;    struct request_para *para;         para = (struct request_para *)malloc( sizeof(struct request_para) );    if(NULL == para)        return 0;    bzero(para,sizeof(struct request_para));     //创建一个时间轮    pwheel = ti_timewheel_create();    if(NULL == pwheel)        return -1;       //添加一个定时器    para->val = 100;    para->timer = ti_add_timer(pwheel, 3000, &mytimer, (unsigned long)para);        while(1)    {        sleep(2);    }     //释放时间轮    ti_timewheel_release(pwheel);        return 0;}
3.4 编译运行
toney@ubantu:/mnt/hgfs/em嵌入式学习记录/4. timerwheel/2. 多级时间轮$ lsa.out  list.h  log.h  mutiTimeWheel.ctoney@ubantu:/mnt/hgfs/em嵌入式学习记录/4. timerwheel/2. 多级时间轮$ gcc mutiTimeWheel.c -lpthreadtoney@ubantu:/mnt/hgfs/em嵌入式学习记录/4. timerwheel/2. 多级时间轮$ ./a.out [#DEBUG: Toeny Sun: mytimer:370]:100[#DEBUG: Toeny Sun: mytimer:370]:100[#DEBUG: Toeny Sun: mytimer:370]:100[#DEBUG: Toeny Sun: mytimer:370]:100[#DEBUG: Toeny Sun: mytimer:370]:100[#DEBUG: Toeny Sun: mytimer:370]:100[#DEBUG: Toeny Sun: mytimer:370]:100[#DEBUG: Toeny Sun: mytimer:370]:100[#DEBUG: Toeny Sun: mytimer:370]:100[#DEBUG: Toeny Sun: mytimer:370]:100[#DEBUG: Toeny Sun: mytimer:370]:100[#DEBUG: Toeny Sun: mytimer:370]:100[#DEBUG: Toeny Sun: mytimer:370]:100[#DEBUG: Toeny Sun: mytimer:370]:100[#DEBUG: Toeny Sun: mytimer:370]:100[#DEBUG: Toeny Sun: mytimer:370]:100[#DEBUG: Toeny Sun: mytimer:370]:100[#DEBUG: Toeny Sun: mytimer:370]:100[#DEBUG: Toeny Sun: mytimer:370]:100[#DEBUG: Toeny Sun: mytimer:370]:100[#DEBUG: Toeny Sun: mytimer:370]:100[#DEBUG: Toeny Sun: mytimer:370]:100[#DEBUG: Toeny Sun: mytimer:370]:100[#DEBUG: Toeny Sun: mytimer:370]:100[#DEBUG: Toeny Sun: mytimer:370]:100[#DEBUG: Toeny Sun: mytimer:370]:100[#DEBUG: Toeny Sun: mytimer:370]:100[#DEBUG: Toeny Sun: mytimer:370]:100
"怎么用C语言实现经典多级时间轮定时器"的内容就介绍到这里了，感谢大家的阅读。如果想了解更多行业相关的知识可以关注网站，小编将为大家输出更多高质量的实用文章！