/*redis里的回调函数*/#include<stdio.h>#include<stdlib.h>    static void zmalloc_default_oom(size_t size) {    printf("zmalloc_default_oom\n");    fprintf(stderr, "zmalloc: Out of memory trying to allocate %d bytes\n",size);    fflush(stderr);}  static void (*zmalloc_oom_handler)(size_t) = zmalloc_default_oom;    void zmalloc_set_oom_handler(void (*oom_handler)(size_t)) {    printf("zmalloc_set_oom_handler\n");    zmalloc_oom_handler = oom_handler;}  void redisOutOfMemoryHandler(size_t allocation_size) {    printf("redisOutOfMemoryHandler------:%d\n",allocation_size);}  int main(void){    //zmalloc_set_oom_handler(redisOutOfMemoryHandler);    zmalloc_oom_handler(10);    getchar();    return 0;}

int main(void){    zmalloc_set_oom_handler(redisOutOfMemoryHandler);    zmalloc_oom_handler(10);    getchar();    return 0;}

int main(int argc, char **argv) {    struct timeval tv;                     /* We need to initialize our libraries, and the server configuration. */#ifdef INIT_SETPROCTITLE_REPLACEMENT    //初始化参数    spt_init(argc, argv);#endif    setlocale(LC_COLLATE,"");    /*    zmalloc_enable_thread_safeness()    开启了内存分配管理的线程安全变量，当内存分配时，    redis会统计一个总内存分配量，这是一个共享资源，    所以需要原子性操作，在redis的内存分配代码里，    当需要原子操作时，就需要打开线程安全变量。    */    zmalloc_enable_thread_safeness();    /*    zmalloc_set_oom_handler()    是一个内存分配错误处理，    当无法得到需要的内存量时，    会调用redisOutOfMemoryHandler函数。    */    zmalloc_set_oom_handler(redisOutOfMemoryHandler);    srand(time(NULL)^getpid());    gettimeofday(&tv,NULL);    dictSetHashFunctionSeed(tv.tv_sec^tv.tv_usec^getpid());    server.sentinel_mode = checkForSentinelMode(argc,argv);    initServerConfig();    ..........}

zmalloc_set_oom_handler注册回调函数

redisOutOfMemoryHandler主要是个log日志打印，即在内存分配失败的时候触发回调函数，打印log。

void *zmalloc(size_t size) {    void *ptr = malloc(size+PREFIX_SIZE);     if (!ptr) zmalloc_oom_handler(size);#ifdef HAVE_MALLOC_SIZE    update_zmalloc_stat_alloc(zmalloc_size(ptr));    return ptr;#else    *((size_t*)ptr) = size;    update_zmalloc_stat_alloc(size+PREFIX_SIZE);    return (char*)ptr+PREFIX_SIZE;#endif}

#include <stdio.h>#include <stdlib.h>#include <stdarg.h> /* Log levels */#define REDIS_DEBUG 0#define REDIS_VERBOSE 1#define REDIS_NOTICE 2#define REDIS_WARNING 3  #define REDIS_MAX_LOGMSG_LEN    1024 /* 默认信息长度 */ void redisLogRaw(int level, const char *msg);void redisLog(int level, const char *fmt, ...); /*verbosity表示开启log的级别需要写log的时候，log级别小于等于verbosity写log否则不会写log */struct redisServer {    int verbosity;                  /* 日志级别*/    char *logfile;                  /* Path of log file */}; struct redisServer server; /* server global state */  void redisLog(int level, const char *fmt, ...) {    //如果level级别大于verbosity则不打印    if (level> server.verbosity)     {        return;    }    va_list ap;    char msg[REDIS_MAX_LOGMSG_LEN];      va_start(ap, fmt);    vsnprintf(msg, sizeof(msg), fmt, ap);    va_end(ap);     redisLogRaw(level,msg);} void redisLogRaw(int level, const char *msg) {#if 1         FILE *fp;    char buf[64];//  int rawmode = (level & REDIS_LOG_RAW);    //int log_to_stdout = server.logfile[0] == ‘\0‘;     //level &= 0xff; /* clear flags */    //if (level < server.verbosity) return;    if(server.logfile != NULL)    {        fp=fopen(server.logfile,"a");    }    else    {        fp=stdout;    }          int off;//  struct timeval tv;     //gettimeofday(&tv,NULL);    //off = strftime(buf,sizeof(buf),"%d %b %H:%M:%S.",localtime(&tv.tv_sec));    //snprintf(buf+off,sizeof(buf)-off,"%03d",(int)tv.tv_usec/1000);    //fprintf(fp,"[%d] %s %c %s\n",(int)getpid(),buf,c[level],msg);    fprintf(fp," %s\n",msg);    fflush(fp);     if(server.logfile != NULL)    {        fclose(fp);    }      #endif}int main(void){    server.verbosity=2;    server.logfile=NULL;    redisLog(1,"11111111\n");    redisLog(2,"22222\n");    redisLog(3,"333\n");    getchar();         return 0;}