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!
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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)=2^32 struct 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 void list_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 void list_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 void list_del(struct list_head *entry) { __list_del(entry->prev, entry->next); } static inline void list_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 int list_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)=2^32 struct 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; i vec[i]); } static void init_tvn_list(struct tvec * tvn) { int i; for( i = 0; i vec[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$ ls a.out list.h log.h mutiTimeWheel.c toney@ubantu:/mnt/hgfs/em嵌入式学习记录/4. timerwheel/2. 多级时间轮$ gcc mutiTimeWheel.c -lpthread toney@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创新互联网站,小编将为大家输出更多高质量的实用文章!
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