{"id":840,"date":"2020-11-02T17:15:06","date_gmt":"2020-11-02T09:15:06","guid":{"rendered":"http:\/\/www.wangkaixuan.tech\/?p=840"},"modified":"2020-11-04T09:23:50","modified_gmt":"2020-11-04T01:23:50","slug":"%e5%87%a0%e7%a7%8d%e5%8f%96%e6%97%b6%e9%97%b4%e7%9a%84%e6%96%b9%e6%b3%95%ef%bc%88%e9%99%84%e4%bb%a3%e7%a0%81%ef%bc%89","status":"publish","type":"post","link":"http:\/\/www.wangkaixuan.tech\/?p=840","title":{"rendered":"\u51e0\u79cd\u53d6\u65f6\u95f4\u7684\u65b9\u6cd5\uff08\u9644\u4ee3\u7801\uff09"},"content":{"rendered":"\n<h2 class=\"wp-block-heading\">1.\u4e0a\u53e4\u7248<\/h2>\n\n\n\n<p>\u6700\u539f\u59cb\u7684\u53d6\u65f6\u95f4\u7684\u65b9\u6cd5\u5927\u6982\u5c31\u662ftime+localtime\u4e86\uff0c\u89c1\u4ee3\u7801\uff1a<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>#include &lt;stdio.h>\n#include &lt;time.h>\n\n\/\/ gcc -o time_1 time_1.c\n\nint main()\n{\n    time_t tm_now;\n\n    time(&amp;tm_now);\/\/ \u6216\u8005\u5199\u6210 tm_now = time(NULL);\n\n    \/\/1.\u76f4\u63a5\u6253\u5370\uff1a1970-1-1,00:00:00\u5230\u73b0\u5728\u7684\u79d2\u6570\n    printf(\"now time is %ld second\\n\", tm_now);\n\n    \/\/2.\u8f6c\u6362\u6210\u672c\u5730\u65f6\u95f4\uff0c\u7cbe\u786e\u5230\u79d2\n    struct tm *p_local_tm ;\n    p_local_tm = localtime(&amp;tm_now) ;\n    printf(\"now datetime: %04d-%02d-%02d %02d:%02d:%02d\\n\",\n        p_local_tm->tm_year+1900, \n        p_local_tm->tm_mon+1, \n        p_local_tm->tm_mday, \n        p_local_tm->tm_hour, \n        p_local_tm->tm_min, \n        p_local_tm->tm_sec);\n \n    return 0;\n}<\/code><\/pre>\n\n\n\n<p>\u5176\u4e2dtime\u51fd\u6570\u8fd4\u56de\u7684\u662f1970\u5e74\u5230\u73b0\u5728\u7684\u79d2\u6570\uff0c\u7cbe\u786e\u5230\u79d2\u3002<\/p>\n\n\n\n<p>localtime\u51fd\u6570\u662f\u6839\u636e\u8fd9\u4e2a\u79d2\u6570\u548c\u672c\u673a\u7684\u65f6\u533a\uff0c\u89e3\u6790\u51fa\u5e74\u6708\u65e5\u65f6\u5206\u79d2\u7b49\u4fe1\u606f\u3002<\/p>\n\n\n\n<p>\u8fd9\u91cc\u7279\u522b\u63d0\u9192\u4e00\u70b9\uff0clocaltime\u51fd\u6570\u4e0d<strong>\u662f\u591a\u7ebf\u7a0b\u5b89\u5168\u7684<\/strong>\uff0clocaltime_r\u624d\u662f\u3002<\/p>\n\n\n\n<p>\u8fd8\u8981\u7279\u522b\u63d0\u9192\u4e00\u70b9\uff0c\u4e0d\u8981\u5728<strong>\u4fe1\u53f7\u54cd\u5e94\u51fd\u6570<\/strong>\u4e2d\u4f7f\u7528localtime\u6216localtime_r\uff0c\u7a0b\u5e8f\u4f1a\u5361\u6b7b\uff01<\/p>\n\n\n\n<p>\u7a0b\u5e8f\u8fd0\u884c\u7ed3\u679c\u5982\u4e0b\uff1a<\/p>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"474\" height=\"51\" src=\"http:\/\/www.wangkaixuan.tech\/wp-content\/uploads\/2020\/11\/image-1.png\" alt=\"\" class=\"wp-image-848\"\/><\/figure>\n\n\n\n<h2 class=\"wp-block-heading\">2.\u50bb\u74dc\u7248<\/h2>\n\n\n\n<p>\u53e6\u4e00\u4e2a\u6bd4\u8f83\u597d\u7528\u7684\u51fd\u6570\u662fgettimeofday\u3002<\/p>\n\n\n\n<p>\u76f8\u6bd4\u5176\u4ed6\u51fd\u6570\uff0cgettimeofday\u53ef\u4ee5\u7cbe\u786e\u5230\u5fae\u79d2\uff0c\u8fd8\u53ef\u4ee5\u6307\u5b9a\u65f6\u533a\uff0c\u6027\u80fd\u4e5f\u8fd8\u53ef\u4ee5\uff0c\u53ef\u4ee5\u6ee1\u8db3\u7edd\u5927\u591a\u6570\u573a\u666f\uff0c\u56e0\u6b64\u53eb\u50bb\u74dc\u7248\u3002<\/p>\n\n\n\n<p>\u793a\u4f8b\u4ee3\u7801\u5982\u4e0b\uff1a<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>#include &lt;stdio.h>\n#include &lt;sys\/time.h>\n#include &lt;time.h>\n\n\/\/ gcc -o time_2 time_2.c\n\nint main()\n{\n    struct timeval tm_now;\n\n    \/\/1.\u83b7\u53d6\u5f53\u524d\u65f6\u95f4\u6233(tv_sec, tv_usec)\n    gettimeofday(&amp;tm_now,NULL); \/\/ \u7b2c\u4e8c\u4e2a\u53c2\u6570\u662f\u65f6\u533a\n\n    \/\/2.\u8f6c\u6362\u6210\u672c\u5730\u65f6\u95f4\uff0c\u7cbe\u786e\u5230\u79d2\n    struct tm *p_local_tm;\n    p_local_tm = localtime(&amp;tm_now.tv_sec) ;\n    printf(\"now datetime: %04d-%02d-%02d %02d:%02d:%02d.%06ld\\n\",\n        p_local_tm->tm_year+1900, \n        p_local_tm->tm_mon+1, \n        p_local_tm->tm_mday, \n        p_local_tm->tm_hour, \n        p_local_tm->tm_min, \n        p_local_tm->tm_sec,\n        tm_now.tv_usec); \/\/ \u6709\u5fae\u79d2\u65f6\u95f4\u6233\u4e86\n \n    return 0;\n}<\/code><\/pre>\n\n\n\n<p>\u8fd0\u884c\u7ed3\u679c\u5982\u4e0b\uff1a<\/p>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"490\" height=\"34\" src=\"http:\/\/www.wangkaixuan.tech\/wp-content\/uploads\/2020\/11\/image.png\" alt=\"\" class=\"wp-image-847\"\/><\/figure>\n\n\n\n<h2 class=\"wp-block-heading\">3.\u8fdb\u9636\u7248<\/h2>\n\n\n\n<p>\u5982\u679c\u5fae\u79d2\u7ea7\u522b\u7684\u7cbe\u5ea6\u8fd8\u4e0d\u6ee1\u8db3\u8981\u6c42\uff0c\u53ef\u4ee5\u5c1d\u8bd5\u4e0bclock_gettime\uff0c\u4ee3\u7801\u5982\u4e0b\uff1a<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>#include &lt;stdio.h>\n#include &lt;unistd.h>\n#include &lt;time.h>\n\n\/\/ gcc -o time_3 time_3.c\n\nvoid print_timestamp(int use_monotonic)\n{\n    struct timespec tm_now;\n\n    \/\/1.\u83b7\u53d6\u5f53\u524d\u65f6\u95f4\u6233(tv_sec, tv_usec)\n    if(use_monotonic)\n        clock_gettime(CLOCK_MONOTONIC, &amp;tm_now); \/\/ \u5355\u8c03\u65f6\u95f4\uff0c\u5c4f\u853d\u624b\u52a8\u4fee\u6539\u65f6\u95f4\n    else\n        clock_gettime(CLOCK_REALTIME, &amp;tm_now); \/\/ \u673a\u5668\u65f6\u95f4\n\n    \/\/2.\u8f6c\u6362\u6210\u672c\u5730\u65f6\u95f4\uff0c\u7cbe\u786e\u5230\u79d2\n    struct tm *p_local_tm;\n    p_local_tm = localtime(&amp;tm_now.tv_sec) ;\n    printf(\"now datetime: %04d-%02d-%02d %02d:%02d:%02d.%09ld\\n\",\n        p_local_tm->tm_year+1900, \n        p_local_tm->tm_mon+1, \n        p_local_tm->tm_mday, \n        p_local_tm->tm_hour, \n        p_local_tm->tm_min, \n        p_local_tm->tm_sec,\n        tm_now.tv_nsec); \/\/ \u6709\u7eb3\u79d2\u65f6\u95f4\u6233\u4e86\n}\n\nint main(int argc, char **argv)\n{\n    int use_monotonic = 0;\n\n    int optval  = 0;\n    while ((optval = getopt(argc, argv, \"Mm\")) != EOF)\n    {\n\t\tswitch (optval) \n        {\n\t\t\tcase 'M':\n\t\t\tcase 'm':\n                use_monotonic = 1;\n                break;\n            default:\n                break;\n        }\n    }\n\n    while(1)\n    {\n        print_timestamp(use_monotonic);\n        sleep(1);\n    }\n \n    return 0;\n}<\/code><\/pre>\n\n\n\n<p>\u8fd0\u884c\u7ed3\u679c\u5982\u4e0b\uff1a<\/p>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"493\" height=\"132\" src=\"http:\/\/www.wangkaixuan.tech\/wp-content\/uploads\/2020\/11\/image-2.png\" alt=\"\" class=\"wp-image-849\"\/><\/figure>\n\n\n\n<p>clock_gettime\u7684\u7b2c\u4e00\u4e2a\u53c2\u6570\u53ef\u4ee5\u6307\u5b9a\u4e00\u4e2aclock_id\u53c2\u6570:<\/p>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"532\" height=\"31\" src=\"http:\/\/www.wangkaixuan.tech\/wp-content\/uploads\/2020\/11\/image-3.png\" alt=\"\" class=\"wp-image-850\"\/><\/figure>\n\n\n\n<p>\u5e38\u89c1\u7684\u6709\u4e24\u4e2a\uff1a<\/p>\n\n\n\n<p>1) CLOCK_REALTIME<\/p>\n\n\n\n<p>\u5373\u666e\u901a\u7684\u65f6\u95f4\uff0c\u8ddf\u5176\u4ed6\u65f6\u95f4\u51fd\u6570\u53d6\u51fa\u6765\u7684\u65f6\u95f4\u5e76\u65e0\u533a\u522b\uff0c\u8fd0\u884c\u6548\u679c\u5982\u4e0a\u3002<\/p>\n\n\n\n<p>2) CLOCK_MONOTONIC<\/p>\n\n\n\n<p>\u5373\u5355\u8c03\u65f6\u95f4\uff0c\u8ddf\u7cfb\u7edf\u7684\u542f\u52a8\u65f6\u95f4\u6709\u5173\uff0c\u4e0d\u53d7\u624b\u52a8\u4fee\u6539\u7cfb\u7edf\u65f6\u95f4\u7684\u5f71\u54cd\u3002<\/p>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"507\" height=\"71\" src=\"http:\/\/www.wangkaixuan.tech\/wp-content\/uploads\/2020\/11\/image-4.png\" alt=\"\" class=\"wp-image-851\"\/><\/figure>\n\n\n\n<p>\u5982\u4e0a\u56fe\uff0c\u8868\u793a\u7cfb\u7edf\u5df2\u7ecf\u542f\u52a8\u4e8624:09\uff088\u70b9\u662f\u56e0\u4e3a\u6211\u4eec\u5728\u4e1c8\u533a\uff09\u3002<\/p>\n\n\n\n<p>\u6211\u4eec\u7528date\u547d\u4ee4\u5c06\u65f6\u95f4\u5f80\u56de\u4fee\u6539\uff0c\u89c2\u5bdf\u4e24\u8005\u7684\u8f93\u51fa\u7ed3\u679c\uff1a<\/p>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"368\" height=\"113\" src=\"http:\/\/www.wangkaixuan.tech\/wp-content\/uploads\/2020\/11\/image-5.png\" alt=\"\" class=\"wp-image-852\"\/><\/figure>\n\n\n\n<p>\u53ef\u4ee5\u770b\u5230\uff0c\u6307\u5b9a\u4e3aREAL_TIME\u7684\u51fd\u6570\u51fa\u73b0\u4e86\u65f6\u95f4\u56de\u9000\uff08\u4e0a\u56fe\uff09\uff0c\u6307\u5b9a\u4e3aCLOCK_MONOTONIC\u7684\u51fd\u6570\u4e00\u76f4\u5728\u5355\u8c03\u6d41\u901d\uff08\u4e0b\u56fe\uff09\uff1a<\/p>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"357\" height=\"112\" src=\"http:\/\/www.wangkaixuan.tech\/wp-content\/uploads\/2020\/11\/image-6.png\" alt=\"\" class=\"wp-image-853\"\/><\/figure>\n\n\n\n<p>\u8868\u9762\u4e0a\u770b\uff0c\u8fd9\u4e2a\u51fd\u6570\u7cbe\u5ea6\u4e0d\u9519\uff0c\u529f\u80fd\u5b8c\u5907\uff0c\u4f46\u5374\u5b58\u5728\u4e00\u4e2a\u7a81\u51fa\u7f3a\u70b9&#8211;<strong>\u6162<\/strong>\u3002\u5bf9\u4e8e\u6027\u80fd\u654f\u611f\u7684\u51fd\u6570\uff0c\u9891\u7e41\u8c03\u7528\u4f1a\u5f71\u54cd\u6027\u80fd\uff0c\u8fd9\u4e00\u70b9\u6211\u4eec\u540e\u9762\u4ed4\u7ec6\u8bf4\u3002<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">4.\u4e13\u5bb6\u7248<\/h2>\n\n\n\n<p>\u4e13\u5bb6\u7248\u672c\u7684\u8ba1\u65f6\u51fd\u6570\u6709\u4e24\u4e2a\u7a81\u51fa\u4f18\u70b9\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>\u6027\u80fd\u9ad8\uff1a\u7ed5\u8fc7\u5185\u6838\u76f4\u63a5\u8bfb\u5bc4\u5b58\u5668\uff0c\u5f00\u9500\u5f88\u5c0f<\/li><li>\u7cbe\u5ea6\u9ad8\uff1a\u65f6\u95f4\u6d4b\u91cf\u7684\u6700\u5c0f\u5355\u4f4d\u662f<strong>1\/CPU\u9891\u7387<\/strong>\u79d2\uff0c\u53ef\u8fbe0.3\u7eb3\u79d2\uff08\u5047\u8bbeCPU\u9891\u7387\u4e3a3GHz\uff09<\/li><\/ul>\n\n\n\n<p>\u4e0b\u9762\u662f\u793a\u4f8b\u7a0b\u5e8f\uff1a<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>\n#include &lt;stdio.h>\n#include &lt;unistd.h>\n#include &lt;stdlib.h> \/\/ for atof\n#include &lt;stdint.h> \/\/ for uint64_t\n\n\/\/ gcc -o time_4 time_4.c\n\n\/\/\u83b7\u53d6CPU\u9891\u7387\nuint64_t get_cpu_freq()\n{\n    FILE *fp=popen(\"lscpu | grep CPU | grep MHz | awk  {'print $3'}\",\"r\");\n    if(fp == NULL)\n        return 0;\n\n    char cpu_mhz_str&#91;200] = { 0 };\n    fgets(cpu_mhz_str,80,fp);\n    fclose(fp);\n\n    return atof(cpu_mhz_str) * 1000 * 1000;\n}\n\n\/\/\u8bfb\u53d6\u65f6\u95f4\u6233\u5bc4\u5b58\u5668\nuint64_t get_tsc() \/\/ TSC == Time Stamp Counter\u5bc4\u5b58\u5668\n{\n#ifdef __i386__\n    uint64_t x;\n    __asm__ volatile(\"rdtsc\" : \"=A\"(x));\n    return x;\n#elif defined(__amd64__) || defined(__x86_64__)\n    uint64_t a, d;\n    __asm__ volatile(\"rdtsc\" : \"=a\"(a), \"=d\"(d));\n    return (d &lt;&lt; 32) | a;\n#else \/\/ ARM\u67b6\u6784CPU\n    uint32_t cc = 0;\n    __asm__ volatile (\"mrc p15, 0, %0, c9, c13, 0\":\"=r\" (cc));\n    return (uint64_t)cc; \n#endif\n}\n\nint main(int argc, char **argv)\n{\n    uint64_t cpu_freq = get_cpu_freq();\n    printf(\"cpu_freq is %lu\\n\", cpu_freq);\n\n    uint64_t last_tsc = get_tsc(); \n    while(1)\n    {\n        sleep(1);\n        uint64_t cur_tsc = get_tsc(); \n        printf(\"TICK(s)   : %lu\\n\", cur_tsc - last_tsc);\n        printf(\"Second(s) : %.02lf\\n\", 1.0 * (cur_tsc - last_tsc) \/ cpu_freq);\n        last_tsc = cur_tsc;\n    }\n    return 0;\n}<\/code><\/pre>\n\n\n\n<p>TSC\u7684\u5168\u79f0\u662fTime Stamp Counter\uff0c\u5b83\u662f\u4e00\u4e2a\u4fdd\u5b58\u7740CPU\u8fd0\u8f6c\u65f6\u949f\u5468\u671f\u6570\u7684\u5bc4\u5b58\u5668\uff0c\u5728X86\u7b49\u5e73\u53f0\u4e0b\u5747\u6709\u63d0\u4f9b\uff08ARM\u5e73\u53f0\u4e0b\u662fCCR-Cycle Counter Register\uff09\u3002<\/p>\n\n\n\n<p>\u901a\u8fc7\u4e13\u95e8\u7684rdtsc\u6c47\u7f16\u6307\u4ee4\uff0c\u53ef\u7ed5\u8fc7\u64cd\u4f5c\u7cfb\u7edf\u5185\u6838\u76f4\u63a5\u4ece\u5bc4\u5b58\u5668\u4e2d\u8bfb\u53d6\u6570\u503c\uff0c\u56e0\u6b64\u901f\u5ea6\u6781\u5feb\u3002<\/p>\n\n\n\n<p>\u901a\u8fc7\u4e0a\u8ff0\u7684get_tsc\u51fd\u6570\u53ef\u4ee5\u4ece\u8fd9\u4e2a\u5bc4\u5b58\u5668\u4e2d\u8bfb\u51fa\u4e00\u4e2a64\u4f4d\u7684\u6570\u503c\uff0c\u8fde\u7eed\u4e24\u6b21\u8bfb\u53d6\u7684\u503c\u7684\u5dee\u503c\uff0c\u5373\u662f\u8fde\u7eed\u4e24\u6b21\u8c03\u7528\u4e4b\u95f4CPU\u8fd0\u884c\u7684\u5468\u671f\u6570\u3002\u7528\u8fd9\u4e2a\u5468\u671f\u6570\u9664\u4ee5CPU\u8fd0\u884c\u7684\u9891\u7387\uff08\u901a\u8fc7\u4e0a\u9762\u7684get_cpu_freq\u51fd\u6570\u83b7\u5f97\uff09\uff0c\u5373\u53ef\u5f97\u5230\u5177\u4f53\u7684\u79d2\u6570\u3002<\/p>\n\n\n\n<p>\u4e0a\u8ff0\u4ee3\u7801\u8fd0\u884c\u6548\u679c\u5982\u4e0b\uff1a<\/p>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"484\" height=\"195\" src=\"http:\/\/www.wangkaixuan.tech\/wp-content\/uploads\/2020\/11\/image-8.png\" alt=\"\" class=\"wp-image-856\"\/><\/figure>\n\n\n\n<p>\u53ef\u4ee5\u770b\u5230\uff0c\u6211\u6d4b\u8bd5\u7528\u7684\u673a\u5668\u7684CPU\u9891\u7387\u662f1.8Ghz\u7684\uff0c\u6211\u6bcfsleep\u4e00\u79d2\u8f93\u51fa\u4e00\u4e0b\u4e24\u6b21CPU\u8ba1\u6570\u5668\u7684\u5dee\u503c\uff0c\u53d1\u73b0\u8ddf\u9891\u7387\u4e5f\u80fd\u5bf9\u7684\u4e0a\u3002<\/p>\n\n\n\n<p>\u4e8b\u5b9e\u4e0a\uff0c\u4e0a\u9762\u7684\u6240\u6709\u53d6\u65f6\u95f4\u7684\u51fd\u6570\uff0c\u90fd\u662f\u57fa\u4e8e\u5e95\u5c42\u7684\u7c7b\u4f3crdtsc\u6307\u4ee4\u5c01\u88c5\u7684\uff0c\u6211\u4eec\u76f4\u63a5\u4f7f\u7528\u6700\u5e95\u5c42\u7684\u547d\u4ee4\uff0c\u56fa\u7136\u5feb\u4e14\u7cbe\u786e\uff0c\u4f46\u662f\u4e5f\u4e0d\u53ef\u907f\u514d\u7684\u8981\u76f4\u9762\u4e00\u4e9b\u5751\u3002<\/p>\n\n\n\n<p>\u6bd4\u5982\u6211\u4eec\u53ef\u80fd\u78b0\u89c1\u591aCPU\u95ee\u9898\u3001\u591a\u7ebf\u7a0b\u95ee\u9898\u3001\u8fdb\u7a0b\u4e0a\u4e0b\u6587\u5207\u6362\u95ee\u9898\uff0c\u8ba1\u7b97\u673a\u4e3b\u52a8\u8c03\u8282CPU\u9891\u7387\u95ee\u9898\u7b49\u3002\u4e3a\u4e86\u987a\u5229\u5730\u4f7f\u7528\u8fd9\u4e2a\u6307\u4ee4\uff0c\u6211\u4eec\u5c31\u8981\u5bf9\u7a0b\u5e8f\u548c\u64cd\u4f5c\u7cfb\u7edf\u505a\u4e00\u7cfb\u5217\u7684\u9650\u5236\uff0c\u6bd4\u5982rdtsc\u7684\u7ed3\u679c\u4e0d\u5728CPU\u95f4\u5171\u4eab\u3001\u8fdb\u7a0b\u8fd0\u884c\u65f6\u7ed1\u5b9aCPU\u4ee5\u907f\u514d\u88ab\u5207\u6362\u5230\u53e6\u5916\u7684CPU\u4e0a\u53bb\u3001\u7981\u6b62\u8ba1\u7b97\u673a\u4e3b\u52a8\u8c03\u9891\u529f\u80fd\u7b49\u3002<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">5.\u5173\u4e8e\u6027\u80fd<\/h2>\n\n\n\n<p>\u6211\u4eec\u5199\u4e86\u4e00\u4e2a\u6d4b\u8bd5\u7a0b\u5e8f\uff0c\u8dd110\u4ebf\u6b21\uff0c\u53d6\u5e73\u5747\u65f6\u95f4\uff0c\u5206\u522b\u6d4b\u8bd5\u51e0\u4e2a\u51fd\u6570\u7684\u6027\u80fd\uff1a<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>#include &lt;stdio.h>\n#include &lt;unistd.h>\n#include &lt;stdlib.h> \n#include &lt;stdint.h>\n#include &lt;time.h>\n#include &lt;sys\/time.h>\n\n\/\/ gcc -o time_5 time_5.c\n\nuint64_t get_by_time()\n{\n    time_t tm_now;\n    time(&amp;tm_now);\n    return tm_now;\n}\n\nuint64_t get_by_gettimeofday()\n{\n    struct timeval tm_now;\n    gettimeofday(&amp;tm_now,NULL);\n    return tm_now.tv_sec;\n}\n\nuint64_t get_by_clock_gettime()\n{\n    struct timespec tm_now;\n    clock_gettime(CLOCK_REALTIME, &amp;tm_now);\n    return tm_now.tv_sec;\n}\n\nuint64_t get_cpu_freq()\n{\n    FILE *fp=popen(\"lscpu | grep CPU | grep MHz | awk  {'print $3'}\",\"r\");\n    if(fp == NULL)\n        return 0;\n\n    char cpu_mhz_str&#91;200] = { 0 };\n    fgets(cpu_mhz_str,80,fp);\n    fclose(fp);\n\n    return atof(cpu_mhz_str) * 1000 * 1000;\n}\n\nuint64_t get_by_tsc()\n{\n    uint64_t a, d;\n    __asm__ volatile(\"rdtsc\" : \"=a\"(a), \"=d\"(d));\n    return (d &lt;&lt; 32) | a;\n}\n\nvoid print_diff(uint64_t loop_times, uint64_t beg_tsc, uint64_t end_tsc)\n{   \n    double tt_ns = (end_tsc - beg_tsc) * 1.0 * 1000 * 1000 * 1000 \/ get_cpu_freq();\n    \n    printf(\"Number Loop :   %lu\\n\", loop_times);\n    printf(\"Total Time  :   %.02lf ns\\n\", tt_ns);\n    printf(\"Avg Time    :   %.02lf ns\\n\", tt_ns \/ loop_times);\n}\n\n#define LOOP_TIMES 1000000000\n\nint main(int argc, char **argv)\n{\n    uint64_t beg_tsc, end_tsc;\n    long loop;\n\n    printf(\"-------------time()-------------\\n\");\n    loop = LOOP_TIMES;\n    beg_tsc = get_by_tsc(); \n    while(loop--)\n        get_by_time();\n    end_tsc = get_by_tsc();\n    print_diff(LOOP_TIMES, beg_tsc, end_tsc);\n\n    printf(\"-------------gettimeofday()-------------\\n\");\n    loop = LOOP_TIMES;\n    beg_tsc = get_by_tsc(); \n    while(loop--)\n        get_by_gettimeofday();\n    end_tsc = get_by_tsc();\n    print_diff(LOOP_TIMES, beg_tsc, end_tsc);\n\n    printf(\"-------------clock_gettime()-------------\\n\");\n    loop = LOOP_TIMES;\n    beg_tsc = get_by_tsc(); \n    while(loop--)\n        get_by_clock_gettime();\n    end_tsc = get_by_tsc();\n    print_diff(LOOP_TIMES, beg_tsc, end_tsc);\n    \n    printf(\"-------------rdtsc-------------\\n\");\n    loop = LOOP_TIMES;\n    beg_tsc = get_by_tsc(); \n    while(loop--)\n        get_by_tsc();\n    end_tsc = get_by_tsc();\n    print_diff(LOOP_TIMES, beg_tsc, end_tsc);\n    \n    return 0;\n}<\/code><\/pre>\n\n\n\n<p>\u6d4b\u8bd5\u7ed3\u679c\u5982\u4e0b\uff1a<\/p>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"499\" height=\"275\" src=\"http:\/\/www.wangkaixuan.tech\/wp-content\/uploads\/2020\/11\/image-9.png\" alt=\"\" class=\"wp-image-857\"\/><\/figure>\n\n\n\n<p>\u53ef\u4ee5\u770b\u5230\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>time\u51fd\u6570\u6700\u5feb\uff0c\u4f46\u662f\u7cbe\u5ea6\u592a\u4f4e<\/li><li>gettimeofday\u548cclock_gettime\u867d\u7136\u7cbe\u5ea6\u9ad8\uff0c\u4f46\u662f\u90fd\u6bd4\u8f83\u6162<\/li><li>rdtsc\u7cbe\u5ea6\u548c\u901f\u5ea6\u90fd\u5341\u5206\u4f18\u79c0<\/li><\/ul>\n\n\n\n<p>\u53e6\u5916\u9700\u8981\u6ce8\u610f\u4e00\u70b9\u7684\u662f\uff0c\u4e0a\u8ff0\u6d4b\u8bd5\u7ed3\u679c\u8ddf\u673a\u5668\u914d\u7f6e\u6709\u5f88\u5927\u5173\u7cfb\uff0c\u6211\u6d4b\u8bd5\u6240\u7528\u7684\u673a\u5668\u662f\u4e00\u53f0ubuntu\u865a\u62df\u673a\uff0cCPU\u53ea\u67091.8GHz\u3002<\/p>\n\n\n\n<p>\u5173\u4e8e\u8fd9\u4e2a\u6d4b\u8bd5\u7ed3\u679c\uff0c\u8fd8\u6709\u5f88\u591a\u5185\u5bb9\u672a\u660e\u786e\uff0c\u6bd4\u5982time\u4e3a\u4ec0\u4e48\u8fd9\u4e48\u5feb\uff0cgettimeofday\u4e0d\u662f\u6709\u7f13\u5b58\u4e48\uff1f\u4e3a\u5565\u8fd8\u8fd9\u4e48\u6162\uff1fclock_gettime\u6309\u8bf4\u5e94\u8be5\u6bd4gettimeofday\u6162\u7684\uff0c\u600e\u4e48\u6d4b\u8bd5\u7ed3\u679c\u5e76\u975e\u5982\u6b64\u5462\uff1frdtsc\u5728\u5404\u4e2a\u51fa\u9519\u573a\u666f\u4e0b\u7a76\u7adf\u662f\u600e\u6837\u5177\u4f53\u7684\u73b0\u8c61\uff1f\u4e0a\u8ff0\u7684\u6d4b\u8bd5\u65b9\u6cd5\u662f\u5426\u79d1\u5b66\u7b49\u3002\u8fd9\u4e9b\u95ee\u9898\u7559\u5f85\u540e\u7eed\u8865\u5168\u3002<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">6.\u53c2\u8003\u8d44\u6599<\/h2>\n\n\n\n<ul class=\"wp-block-list\"><li>\u5173\u4e8eTSC\u7684\u7ef4\u57fa\u9875\u9762\uff1a<a href=\"https:\/\/en.wikipedia.org\/wiki\/Time_Stamp_Counter\">\u94fe\u63a5<\/a><\/li><li>\u8bfb\u53d6TSC\u7684\u591a\u5e73\u53f0\u5b9e\u73b0\uff1a<a href=\"http:\/\/www.fftw.org\/cycle.h\">\u94fe\u63a5<\/a><\/li><li>\u5173\u4e8eTSC\u8de8\u6838\u5fc3\u5b89\u5168\u6027\u7684\u4e00\u4e2a\u95ee\u7b54\uff1a<a href=\"https:\/\/stackoverflow.com\/questions\/3388134\/rdtsc-accuracy-across-cpu-cores\">\u94fe\u63a5<\/a><\/li><li>\u8fd9\u91cc\u662f\u67d0\u5f00\u6e90\u5e93\u7684\u4e00\u4e2a\u5b9e\u73b0\uff08getTSC\u51fd\u6570\uff09\uff1a<a href=\"https:\/\/github.com\/Scalnyx\/simplx\/blob\/master\/include\/trz\/engine\/internal\/linux\/platform_gcc.h\">\u94fe\u63a5<\/a><\/li><\/ul>\n","protected":false},"excerpt":{"rendered":"<p>1.\u4e0a\u53e4\u7248 \u6700\u539f\u59cb\u7684\u53d6\u65f6\u95f4\u7684\u65b9\u6cd5\u5927\u6982\u5c31\u662ftime+localtime\u4e86\uff0c\u89c1\u4ee3\u7801\uff1a \u5176\u4e2dtime\u51fd\u6570\u8fd4\u56de\u7684\u662f1970\u5e74\u5230\u73b0\u5728\u7684\u79d2\u6570\uff0c\u7cbe\u786e\u5230\u79d2\u3002 localtime&#8230;<\/p>\n<p class=\"read-more\"><a class=\"btn btn-default\" href=\"http:\/\/www.wangkaixuan.tech\/?p=840\"> Read More<span class=\"screen-reader-text\">  Read More<\/span><\/a><\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[14],"tags":[],"class_list":["post-840","post","type-post","status-publish","format-standard","hentry","category-05-01-"],"_links":{"self":[{"href":"http:\/\/www.wangkaixuan.tech\/index.php?rest_route=\/wp\/v2\/posts\/840","targetHints":{"allow":["GET"]}}],"collection":[{"href":"http:\/\/www.wangkaixuan.tech\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/www.wangkaixuan.tech\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/www.wangkaixuan.tech\/index.php?rest_route=\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"http:\/\/www.wangkaixuan.tech\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=840"}],"version-history":[{"count":0,"href":"http:\/\/www.wangkaixuan.tech\/index.php?rest_route=\/wp\/v2\/posts\/840\/revisions"}],"wp:attachment":[{"href":"http:\/\/www.wangkaixuan.tech\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=840"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/www.wangkaixuan.tech\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=840"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/www.wangkaixuan.tech\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=840"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}