{"id":2851,"date":"2011-04-04T15:39:03","date_gmt":"2011-04-04T07:39:03","guid":{"rendered":"http:\/\/edsionte.com\/techblog\/?p=2851"},"modified":"2011-09-26T20:28:42","modified_gmt":"2011-09-26T12:28:42","slug":"linux2-6%e8%bf%9b%e7%a8%8b%e8%b0%83%e5%ba%a6%e5%88%86%e6%9e%902-%e8%b0%83%e5%ba%a6%e7%ae%97%e6%b3%95","status":"publish","type":"post","link":"http:\/\/edsionte.com\/techblog\/archives\/2851","title":{"rendered":"Linux2.6\u8fdb\u7a0b\u8c03\u5ea6\u5206\u6790(2)-\u8c03\u5ea6\u7b97\u6cd5"},"content":{"rendered":"

2.\u6570\u636e\u7ed3\u6784<\/h3>\n

O(1)\u8c03\u5ea6\u7b97\u6cd5\u901a\u8fc7\u51e0\u4e2a\u6570\u636e\u7ed3\u6784\u53ef\u4ee5\u5de7\u5999\u7684\u5b9e\u73b0\u5e38\u6570\u7ea7\u7684\u590d\u6742\u5ea6\u3002<\/p>\n

2.1\u53ef\u8fd0\u884c\u961f\u5217<\/h4>\n

\u8c03\u5ea6\u7a0b\u5e8f\u6bcf\u6b21\u5728\u8fdb\u7a0b\u53d1\u751f\u5207\u6362\u65f6\uff0c\u90fd\u8981\u5728\u5c31\u7eea\u961f\u5217\u4e2d\u9009\u53d6\u4e00\u4e2a\u6700\u4f73\u7684\u8fdb\u7a0b\u6765\u8fd0\u884c\u3002Linux\u5185\u6838\u4f7f\u7528runqueue\u6570\u636e\u7ed3\u6784\uff08\u5728\u6700\u65b0\u5185\u6838\u4e2d\u8be5\u7ed3\u6784\u4e3arq\uff09\u8868\u793a\u4e00\u4e2a\u53ef\u8fd0\u884c\u961f\u5217\uff08\u4e5f\u5c31\u662f\u5c31\u7eea\u961f\u5217\uff09\uff0c\u6bcf\u4e2aCPU\u90fd\u6709\u4e14\u53ea\u6709\u4e00\u4e2a\u8fd9\u6837\u7684\u7ed3\u6784\u3002\u8be5\u7ed3\u6784\u4e0d\u4ec5\u63cf\u8ff0\u4e86\u6bcf\u4e2a\u5904\u7406\u5668\u4e2d\u5904\u4e8e\u53ef\u8fd0\u884c\u72b6\u6001\uff08TASK_RUNNING\uff09\u7684\u8fdb\u7a0b\u94fe\u8868\uff0c\u800c\u4e14\u8fd8\u63cf\u8ff0\u4e86\u8be5\u5904\u7406\u5668\u7684\u8c03\u5ea6\u4fe1\u606f\u3002\u4e0b\u9762\u5bf9\u8be5\u7ed3\u6784\u4e2d\u7684\u90e8\u5206\u5b57\u6bb5\u4f5c\u8be6\u7ec6\u63cf\u8ff0\u3002<\/p>\n

spinlock_t lock<\/strong>\uff1a\u4fdd\u62a4\u8fdb\u7a0b\u94fe\u8868\u7684\u81ea\u65cb\u9501\uff1b
\nunsigned long nr_running<\/strong>\uff1a\u8fd0\u884c\u961f\u5217\u94fe\u8868\u4e2d\u8fdb\u7a0b\u6570\u91cf\uff1b
\nunsigned long long nr_switches<\/strong>\uff1aCPU\u6267\u884c\u8fdb\u7a0b\u5207\u6362\u7684\u6b21\u6570\uff1b
\nunsigned long nr_uninterruptible<\/strong>\uff1a\u4e4b\u524d\u5728\u8fd0\u884c\u961f\u5217\u94fe\u8868\u4e2d\u800c\u73b0\u5728\u5904\u4e8e\u91cd\u5ea6\u7761\u7720\u72b6\u6001\u7684\u8fdb\u7a0b\u603b\u6570\uff1b
\nunsigned long expired_timestamp<\/strong>\uff1a\u8fc7\u671f\u961f\u5217\u4e2d\u6700\u8001\u7684\u8fdb\u7a0b\u88ab\u63d2\u5165\u961f\u5217\u7684\u65f6\u95f4\uff1b
\nunsigned long long timestamp_last_tick<\/strong>\uff1a\u6700\u8fd1\u4e00\u6b21\u5b9a\u65f6\u5668\u7ec8\u7aef\u7684\u65f6\u95f4\uff1b
\ntask_t *curr<\/strong>\uff1a\u6307\u5411\u672c\u5730CPU\u5f53\u524d\u6b63\u5728\u8fd0\u884c\u7684\u8fdb\u7a0b\u7684\u8fdb\u7a0b\u63cf\u8ff0\u7b26\uff0c\u5373current\uff1b
\ntask_t *idle<\/strong>\uff1a\u6307\u5411\u672c\u5730CPU\u4e0a\u7684idle\u8fdb\u7a0b\u63cf\u8ff0\u7b26\u7684\u6307\u9488\uff1b
\nstruct mm_struct *prev_mm<\/strong>\uff1a\u5728\u8fdb\u7a0b\u8fdb\u884c\u5207\u6362\u65f6\u7528\u6765\u5b58\u653e\u88ab\u66ff\u6362\u8fdb\u7a0b\u5185\u5b58\u63cf\u8ff0\u7b26\u7684\u5730\u5740\uff1b
\nprio_array_t *active<\/strong>\uff1a\u6307\u5411\u53ef\u8fd0\u884c\u961f\u5217\u4e2d\u6d3b\u52a8\u94fe\u8868\uff1b
\nprio_array_t *expired<\/strong>\uff1a\u6307\u5411\u53ef\u8fd0\u884c\u961f\u5217\u4e2d\u8fc7\u671f\u94fe\u8868\uff1b
\nprio_array_t arrays[2]<\/strong>\uff1a\u8be5\u6570\u7ec4\u7684\u5143\u7d20\u5206\u522b\u8868\u793a\u53ef\u8fd0\u884c\u961f\u5217\u4e2d\u7684\u6d3b\u52a8\u8fdb\u7a0b\u96c6\u5408\u548c\u8fc7\u671f\u8fdb\u7a0b\u96c6\u5408\uff1b
\nint best_expired_prio<\/strong>\uff1a\u8fc7\u671f\u8fdb\u7a0b\u4e2d\u4f18\u5148\u7ea7\u6700\u9ad8\u7684\u8fdb\u7a0b\uff1b<\/p>\n

\u5230\u76ee\u524d\u4e3a\u6b62\uff0c\u4f60\u53ef\u80fd\u5bf9\u4e0a\u8ff0\u5b57\u6bb5\u7684\u7406\u89e3\u8fd8\u4e0d\u662f\u5f88\u6df1\uff0c\u6700\u597d\u7684\u529e\u6cd5\u662f\u5b66\u4e60\u5b8c\u4e0b\u9762\u7684\u5185\u5bb9\u540e\u518d\u56de\u8fc7\u5934\u6765\u91cd\u65b0\u770b\u8fd9\u4e9b\u5b57\u6bb5\u7684\u7528\u9014\u3002\u6211\u4eec\u5728\u4e0a\u9762\u8bf4\u8fc7\uff0crunqueue\u7ed3\u6784\u6700\u4e3b\u8981\u7684\u529f\u80fd\u662f\u63cf\u8ff0\u5904\u4e8e\u53ef\u8fd0\u884c\u72b6\u6001\u8fdb\u7a0b\u6240\u7ec4\u6210\u7684\u94fe\u8868\u3002\u4e0d\u8fc7\uff0c\u6240\u8c13\u7684\u53ef\u8fd0\u884c\u961f\u5217\u5e76\u4e0d\u662f\u5c06\u4e00\u4e9b\u5217\u7684runqueue\u7ed3\u6784\u8fde\u63a5\u5728\u4e00\u4e9b\uff0c\u800c\u662f\u7531runqueue\u7ed3\u6784\u4e2d\u7684arrays\u6570\u7ec4\u6765\u4f53\u73b0\uff0c\u8be5\u6570\u7ec4\u7684\u5143\u7d20\u4e3aprio_array_t\u7c7b\u578b\u3002<\/p>\n

2.2\u4f18\u5148\u7ea7\u6570\u7ec4<\/h4>\n

O(1)\u7b97\u6cd5\u7684\u53e6\u4e00\u4e2a\u6838\u5fc3\u6570\u636e\u7ed3\u6784\u5373\u4e3aprio_array\u7ed3\u6784\u4f53\u3002\u8be5\u7ed3\u6784\u4f53\u4e2d\u6709\u4e00\u4e2a\u7528\u6765\u8868\u793a\u8fdb\u7a0b\u52a8\u6001\u4f18\u5148\u7ea7\u7684\u6570\u7ec4queue\uff0c\u5b83\u5305\u542b\u4e86\u6bcf\u4e00\u79cd\u4f18\u5148\u7ea7\u8fdb\u7a0b\u6240\u5f62\u6210\u7684\u94fe\u8868\u3002<\/p>\n

#define MAX_USER_RT_PRIO        100\r\n#define MAX_RT_PRIO             MAX_USER_RT_PRIO\r\n#define MAX_PRIO                (MAX_RT_PRIO + 40)\r\ntypedef struct prio_array prio_array_t;\r\nstruct prio_array {\r\n        unsigned int nr_active;\r\n        unsigned long bitmap[BITMAP_SIZE];\r\n        struct list_head queue[MAX_PRIO];\r\n};<\/pre>\n
\u7531\u4e8e\u8fdb\u7a0b\u4f18\u5148\u7ea7\u7684\u6700\u5927\u503c\u4e3a139\uff0c\u56e0\u6b64MAX_PRIO\u7684\u6700\u5927\u503c\u53d6140\uff08\u5177\u4f53\u7684\u662f\uff0c\u666e\u901a\u8fdb\u7a0b\u4f7f\u7528100\u5230139\u7684\u4f18\u5148\u7ea7\uff0c\u5b9e\u65f6\u8fdb\u7a0b\u4f7f\u75280\u523099\u7684\u4f18\u5148\u7ea7\uff09\u3002\u56e0\u6b64\uff0cqueue\u6570\u7ec4\u4e2d\u5305\u542b140\u4e2a\u53ef\u8fd0\u884c\u72b6\u6001\u7684\u8fdb\u7a0b\u94fe\u8868\uff0c\u6bcf\u4e00\u6761\u4f18\u5148\u7ea7\u94fe\u8868\u4e0a\u7684\u8fdb\u7a0b\u90fd\u5177\u6709\u76f8\u540c\u7684\u4f18\u5148\u7ea7\uff0c\u800c\u4e0d\u540c\u8fdb\u7a0b\u94fe\u8868\u4e0a\u7684\u8fdb\u7a0b\u90fd\u62e5\u6709\u4e0d\u540c\u7684\u4f18\u5148\u7ea7\u3002<\/p>\n
\u9664\u6b64\u4e4b\u5916\uff0cprio_array\u7ed3\u6784\u4e2d\u8fd8\u5305\u62ec\u4e00\u4e2a\u4f18\u5148\u7ea7\u4f4d\u56febitmap\u3002\u8be5\u4f4d\u56fe\u4f7f\u7528\u4e00\u4e2a\u4f4d\uff08bit\uff09\u6765\u4ee3\u8868\u4e00\u4e2a\u4f18\u5148\u7ea7\uff0c\u800c140\u4e2a\u4f18\u5148\u7ea7\u6700\u5c11\u9700\u89815\u4e2a32\u4f4d\u6765\u8868\u793a\uff0c\u56e0\u6b64BITMAP_SIZE\u7684\u503c\u53d65\u3002\u8d77\u521d\uff0c\u8be5\u4f4d\u56fe\u4e2d\u7684\u6240\u6709\u4f4d\u90fd\u88ab\u7f6e0\uff0c\u5f53\u67d0\u4e2a\u4f18\u5148\u7ea7\u7684\u8fdb\u7a0b\u5904\u4e8e\u53ef\u8fd0\u884c\u72b6\u6001\u65f6\uff0c\u8be5\u4f18\u5148\u7ea7\u6240\u5bf9\u5e94\u7684\u4f4d\u5c31\u88ab\u7f6e1\u3002<\/p>\n
\u56e0\u6b64\uff0cO(1)\u7b97\u6cd5\u4e2d\u67e5\u627e\u7cfb\u7edf\u6700\u9ad8\u7684\u4f18\u5148\u7ea7\u5c31\u8f6c\u5316\u6210\u67e5\u627e\u4f18\u5148\u7ea7\u4f4d\u56fe\u4e2d\u7b2c\u4e00\u4e2a\u88ab\u7f6e1\u7684\u4f4d\u3002\u4e0e2.4\u5185\u6838\u4e2d\u4f9d\u6b21\u6bd4\u8f83\u6bcf\u4e2a\u8fdb\u7a0b\u7684\u4f18\u5148\u7ea7\u4e0d\u540c\uff0c\u7531\u4e8e\u8fdb\u7a0b\u4f18\u5148\u7ea7\u4e2a\u6570\u662f\u5b9a\u503c\uff0c\u56e0\u6b64\u67e5\u627e\u6700\u4f73\u4f18\u5148\u7ea7\u7684\u65f6\u95f4\u6052\u5b9a\uff0c\u5b83\u4e0d\u4f1a\u50cf\u4ee5\u524d\u7684\u65b9\u6cd5\u90a3\u6837\u53d7\u53ef\u6267\u884c\u8fdb\u7a0b\u6570\u91cf\u7684\u5f71\u54cd\u3002<\/p>\n
\u5982\u679c\u786e\u5b9a\u4e86\u4f18\u5148\u7ea7\uff0c\u90a3\u4e48\u9009\u53d6\u4e0b\u4e00\u4e2a\u8fdb\u7a0b\u5c31\u7b80\u5355\u4e86\uff0c\u53ea\u9700\u5728queue\u6570\u7ec4\u4e2d\u5bf9\u5e94\u7684\u94fe\u8868\u4e0a\u9009\u53d6\u4e00\u4e2a\u8fdb\u7a0b\u5373\u53ef\u3002<\/p>\n
2.3\u6d3b\u52a8\u8fdb\u7a0b\u548c\u8fc7\u671f\u8fdb\u7a0b<\/h4>\n
\u5728\u64cd\u4f5c\u7cfb\u7edf\u539f\u7406\u8bfe\u4e0a\u6211\u4eec\u77e5\u9053\uff0c\u5f53\u5904\u4e8e\u8fd0\u884c\u6001\u7684\u8fdb\u7a0b\u7528\u5b8c\u65f6\u95f4\u7247\u540e\u5c31\u4f1a\u5904\u4e8e\u5c31\u7eea\u6001\uff0c\u6b64\u65f6\u8c03\u5ea6\u7a0b\u5e8f\u518d\u4ece\u5c31\u7eea\u6001\u7684\u8fdb\u7a0b\u4e2d\u9009\u53d6\u4e00\u4e2a\u4f5c\u4e3a\u5373\u5c06\u8981\u8fd0\u884c\u7684\u8fdb\u7a0b\u3002<\/p>\n
\u800c\u5728\u5177\u4f53Linux\u5185\u6838\u4e2d\uff0c\u5c31\u7eea\u6001\u548c\u8fd0\u884c\u6001\u7edf\u4e00\u79f0\u4e3a\u53ef\u8fd0\u884c\u6001\uff08TASK_RUNNING\uff09\u3002\u5bf9\u4e8e\u7cfb\u7edf\u5185\u5904\u4e8e\u53ef\u8fd0\u884c\u72b6\u6001\u7684\u8fdb\u7a0b\uff0c\u6211\u4eec\u53ef\u4ee5\u5206\u4e3a\u4e09\u7c7b\uff0c\u9996\u5148\u662f\u6b63\u5904\u4e8e\u6267\u884c\u72b6\u6001\u7684\u90a3\u4e2a\u8fdb\u7a0b\uff1b\u5176\u6b21\uff0c\u6709\u4e00\u90e8\u5206\u5904\u4e8e\u53ef\u8fd0\u884c\u72b6\u6001\u7684\u8fdb\u7a0b\u5219\u8fd8\u6ca1\u6709\u7528\u5b8c\u4ed6\u4eec\u7684\u65f6\u95f4\u7247\uff0c\u4ed6\u4eec\u7b49\u5f85\u88ab\u8fd0\u884c\uff1b\u5269\u4e0b\u7684\u8fdb\u7a0b\u5df2\u7ecf\u7528\u5b8c\u4e86\u81ea\u5df1\u7684\u65f6\u95f4\u7247\uff0c\u5728\u5176\u4ed6\u8fdb\u7a0b\u6ca1\u6709\u7528\u5b8c\u5b83\u4eec\u7684\u65f6\u95f4\u7247\u4e4b\u524d\uff0c\u4ed6\u4eec\u4e0d\u80fd\u518d\u88ab\u8fd0\u884c\u3002<\/p>\n
\u636e\u6b64\uff0c\u6211\u4eec\u5c06\u8fdb\u7a0b\u5206\u4e3a\u4e24\u7c7b\uff0c\u6d3b\u52a8\u8fdb\u7a0b\uff0c\u90a3\u4e9b\u8fd8\u6ca1\u6709\u7528\u5b8c\u65f6\u95f4\u7247\u7684\u8fdb\u7a0b\uff1b\u8fc7\u671f\u8fdb\u7a0b\uff0c\u90a3\u4e9b\u5df2\u7ecf\u7528\u5b8c\u65f6\u95f4\u7247\u7684\u8fdb\u7a0b\u3002\u56e0\u6b64\uff0c\u8c03\u5ea6\u7a0b\u5e8f\u7684\u5de5\u4f5c\u5c31\u662f\u5728\u6d3b\u52a8\u8fdb\u7a0b\u96c6\u5408\u4e2d\u9009\u53d6\u4e00\u4e2a\u6700\u4f73\u4f18\u5148\u7ea7\u7684\u8fdb\u7a0b\uff0c\u5982\u679c\u8be5\u8fdb\u7a0b\u65f6\u95f4\u7247\u6070\u597d\u7528\u5b8c\uff0c\u5c31\u5c06\u8be5\u8fdb\u7a0b\u653e\u5165\u8fc7\u671f\u8fdb\u7a0b\u96c6\u5408\u4e2d\u3002<\/p>\n
\u5728\u53ef\u8fd0\u884c\u961f\u5217\u7ed3\u6784\u4e2d\uff0carrays\u6570\u7ec4\u7684\u4e24\u4e2a\u5143\u7d20\u5206\u522b\u7528\u6765\u8868\u793a\u521a\u624d\u6240\u8ff0\u7684\u6d3b\u52a8\u8fdb\u7a0b\u96c6\u5408\u548c\u8fc7\u671f\u8fdb\u7a0b\u96c6\u5408\uff0cactive\u548cexpired\u4e24\u4e2a\u6307\u9488\u5206\u522b\u76f4\u63a5\u6307\u5411\u8fd9\u4e24\u4e2a\u96c6\u5408\u3002<\/p>\n
\u5173\u4e8e\u53ef\u8fd0\u884c\u961f\u5217\u548c\u4e24\u4e2a\u4f18\u5148\u7ea7\u6570\u7ec4\u7684\u5173\u7cfb\u53ef\u53c2\u8003\u4e0b\u9762\u7684\u56fe\uff1a<\/p>\n
\"\"<\/a><\/p>\n
\u6b63\u5982\u4e0a\u9762\u5206\u6790\u7684\u90a3\u6837\uff0c\u53ef\u8fd0\u884c\u961f\u5217\u7ed3\u6784\u548c\u4f18\u5148\u7ea7\u6570\u7ec4\u7ed3\u6784\u4f7f\u5f97Q(1)\u8c03\u5ea6\u7b97\u6cd5\u5728\u6709\u9650\u7684\u65f6\u95f4\u5185\u5c31\u53ef\u4ee5\u5b8c\u6210\uff0c\u5b83\u4e0d\u4f9d\u8d56\u7cfb\u7edf\u5185\u53ef\u8fd0\u884c\u8fdb\u7a0b\u7684\u6570\u91cf\u3002<\/p>\n
3. \u8c03\u5ea6\u7b97\u6cd5<\/h3>\n
Linux2.4\u7248\u672c\u7684\u5185\u6838\u8c03\u5ea6\u7b97\u6cd5\u7406\u89e3\u8d77\u6765\u7b80\u5355\uff1a\u5728\u6bcf\u6b21\u8fdb\u7a0b\u5207\u6362\u65f6\uff0c\u5185\u6838\u4f9d\u6b21\u626b\u63cf\u5c31\u7eea\u961f\u5217\u4e0a\u7684\u6bcf\u4e00\u4e2a\u8fdb\u7a0b\uff0c\u8ba1\u7b97\u6bcf\u4e2a\u8fdb\u7a0b\u7684\u4f18\u5148\u7ea7\uff0c\u518d\u9009\u62e9\u51fa\u4f18\u5148\u7ea7\u6700\u9ad8\u7684\u8fdb\u7a0b\u6765\u8fd0\u884c\uff1b\u5c3d\u7ba1\u8fd9\u4e2a\u7b97\u6cd5\u7406\u89e3\u7b80\u5355\uff0c\u4f46\u662f\u5b83\u82b1\u8d39\u5728\u9009\u62e9\u4f18\u5148\u7ea7\u6700\u9ad8\u8fdb\u7a0b\u4e0a\u7684\u65f6\u95f4\u5374\u4e0d\u5bb9\u5ffd\u89c6\u3002\u7cfb\u7edf\u4e2d\u53ef\u8fd0\u884c\u7684\u8fdb\u7a0b\u8d8a\u591a\uff0c\u82b1\u8d39\u7684\u65f6\u95f4\u5c31\u8d8a\u5927\uff0c\u65f6\u95f4\u590d\u6742\u5ea6\u4e3aO(n)\u3002\u4f2a\u4ee3\u7801\u5982\u4e0b\uff1a<\/p>\n
for (\u7cfb\u7edf\u4e2d\u7684\u6bcf\u4e2a\u8fdb\u7a0b) {\r\n\t\u91cd\u65b0\u8ba1\u7b97\u65f6\u95f4\u7247;\r\n\t\u91cd\u65b0\u8ba1\u7b97\u4f18\u5148\u7ea7;\r\n}<\/pre>\n
\u800c2.6\u5185\u6838\u6240\u91c7\u7528\u7684O(1)\u7b97\u6cd5\u5219\u5f88\u597d\u7684\u89e3\u51b3\u4e86\u8fd9\u4e2a\u95ee\u9898\uff0c\u8be5\u7b97\u6cd5\u53ef\u4ee5\u5728\u6052\u5b9a\u7684\u65f6\u95f4\u5185\u4e3a\u6bcf\u4e2a\u8fdb\u7a0b\u91cd\u65b0\u5206\u914d\u597d\u65f6\u95f4\u7247\uff0c\u800c\u4e14\u5728\u6052\u5b9a\u7684\u65f6\u95f4\u5185\u53ef\u4ee5\u9009\u53d6\u4e00\u4e2a\u6700\u9ad8\u4f18\u5148\u7ea7\u7684\u8fdb\u7a0b\uff0c\u91cd\u8981\u7684\u662f\u8fd9\u4e24\u4e2a\u8fc7\u7a0b\u90fd\u4e0e\u7cfb\u7edf\u4e2d\u53ef\u8fd0\u884c\u7684\u8fdb\u7a0b\u6570\u65e0\u5173\uff0c\u8fd9\u4e5f\u6b63\u662f\u8be5\u7b97\u6cd5\u53d6\u540d\u4e3aO(1)\u7684\u7f18\u6545\u3002<\/p>\n
3.1 O(1)\u4e2d\u65f6\u95f4\u7247\u7684\u8ba1\u7b97<\/h4>\n
O(1)\u7b97\u6cd5\u91c7\u7528\u8fc7\u671f\u8fdb\u7a0b\u6570\u7ec4\u548c\u6d3b\u8dc3\u8fdb\u7a0b\u6570\u7ec4\u89e3\u51b3\u4ee5\u5f80\u8c03\u5ea6\u7b97\u6cd5\u6240\u5e26\u6765\u7684O(n)\u590d\u6742\u5ea6\u95ee\u9898\u3002\u8fc7\u671f\u6570\u7ec4\u4e2d\u7684\u8fdb\u7a0b\u90fd\u5df2\u7ecf\u7528\u5b8c\u4e86\u65f6\u95f4\u7247\uff0c\u800c\u6d3b\u8dc3\u6570\u7ec4\u7684\u8fdb\u7a0b\u8fd8\u62e5\u6709\u65f6\u95f4\u7247\u3002\u5f53\u4e00\u4e2a\u8fdb\u7a0b\u7528\u5b8c\u81ea\u5df1\u7684\u65f6\u95f4\u7247\u540e\uff0c\u5b83\u5c31\u88ab\u79fb\u52a8\u5230\u8fc7\u671f\u8fdb\u7a0b\u6570\u7ec4\u4e2d\uff0c\u540c\u65f6\u8fd9\u4e2a\u8fc7\u671f\u8fdb\u7a0b\u5728\u88ab\u79fb\u52a8\u4e4b\u524d\u5c31\u5df2\u7ecf\u8ba1\u7b97\u597d\u4e86\u65b0\u7684\u65f6\u95f4\u7247\u3002\u53ef\u4ee5\u770b\u5230O(1)\u8c03\u5ea6\u7b97\u6cd5\u662f\u91c7\u7528\u5206\u6563\u8ba1\u7b97\u65f6\u95f4\u7247\u7684\u65b9\u6cd5\uff0c\u5e76\u4e0d\u50cf\u4ee5\u5f80\u7b97\u6cd5\u4e2d\u96c6\u4e2d\u4e3a\u6240\u6709\u53ef\u8fd0\u884c\u8fdb\u7a0b\u91cd\u65b0\u8ba1\u7b97\u65f6\u95f4\u7247\u3002<\/p>\n
\u5f53\u6d3b\u8dc3\u8fdb\u7a0b\u6570\u7ec4\u4e2d\u6ca1\u6709\u4efb\u4f55\u8fdb\u7a0b\u65f6\uff0c\u8bf4\u660e\u6b64\u65f6\u6240\u6709\u53ef\u8fd0\u884c\u7684\u8fdb\u7a0b\u90fd\u7528\u5b8c\u4e86\u81ea\u5df1\u7684\u65f6\u95f4\u7247\u3002\u90a3\u4e48\u6b64\u65f6\u53ea\u9700\u8981\u4ea4\u6362\u4e00\u4e0b\u4e24\u4e2a\u6570\u7ec4\u5373\u53ef\u5c06\u8fc7\u671f\u8fdb\u7a0b\u5207\u6362\u4e3a\u6d3b\u8dc3\u8fdb\u7a0b\uff0c\u8fdb\u800c\u7ee7\u7eed\u88ab\u8c03\u5ea6\u7a0b\u5e8f\u6240\u8c03\u5ea6\u3002\u4e24\u4e2a\u6570\u7ec4\u4e4b\u95f4\u7684\u5207\u6362\u5176\u5b9e\u5c31\u662f\u6307\u9488\u4e4b\u95f4\u7684\u4ea4\u6362\uff0c\u56e0\u6b64\u82b1\u8d39\u7684\u65f6\u95f4\u662f\u6052\u5b9a\u7684\u3002\u4e0b\u9762\u7684\u4ee3\u7801\u8bf4\u660e\u4e86\u4e24\u4e2a\u6570\u7ec4\u4e4b\u95f4\u7684\u4ea4\u6362\uff1a<\/p>\n
struct prop_array *array = rq->active;\r\nif (array->nr_active != 0) {\r\n\trq->active = rq->expired;\r\n\trq->expired = array;\r\n}<\/pre>\n
\u901a\u8fc7\u5206\u6563\u8ba1\u7b97\u65f6\u95f4\u7247\u3001\u4ea4\u6362\u8fc7\u671f\u548c\u6d3b\u8dc3\u4e24\u4e2a\u8fdb\u7a0b\u96c6\u5408\u7684\u65b9\u6cd5\u53ef\u4ee5\u4f7f\u5f97O(1)\u7b97\u6cd5\u5728\u6052\u5b9a\u7684\u65f6\u95f4\u5185\u4e3a\u6bcf\u4e2a\u8fdb\u7a0b\u91cd\u65b0\u8ba1\u7b97\u597d\u65f6\u95f4\u7247\u3002<\/p>\n
3.2 O(1)\u4e2d\u8fdb\u7a0b\u7684\u9009\u62e9<\/h4>\n
\u8fdb\u7a0b\u8c03\u5ea6\u7684\u672c\u8d28\u5c31\u662f\u5728\u5f53\u524d\u53ef\u8fd0\u884c\u7684\u8fdb\u7a0b\u96c6\u5408\u4e2d\u9009\u62e9\u4e00\u4e2a\u6700\u4f73\u7684\u8fdb\u7a0b\uff0c\u8fd9\u4e2a\u6700\u4f73\u5219\u662f\u4ee5\u8fdb\u7a0b\u7684\u52a8\u6001\u4f18\u5148\u7ea7\u4e3a\u9009\u53d6\u6807\u51c6\u7684\u3002\u4e0d\u7ba1\u662f\u8fc7\u671f\u8fdb\u7a0b\u96c6\u5408\u8fd8\u662f\u6d3b\u8dc3\u8fdb\u7a0b\u96c6\u5408\uff0c\u90fd\u5c06\u6bcf\u4e2a\u4f18\u5148\u7ea7\u7684\u8fdb\u7a0b\u7ec4\u6210\u4e00\u4e2a\u94fe\u8868\uff0c\u56e0\u6b64\u6bcf\u4e2a\u96c6\u5408\u5c31\u6709140\u4e2a\u4e0d\u540c\u4f18\u5148\u7ea7\u7684\u8fdb\u7a0b\u94fe\u8868\u3002\u540c\u65f6\uff0c\u4e24\u4e2a\u96c6\u5408\u4e2d\u8fd8\u91c7\u7528\u4f18\u5148\u7ea7\u4f4d\u56fe\u6765\u6807\u8bb0\u6bcf\u4e2a\u4f18\u5148\u7ea7\u94fe\u8868\u4e2d\u662f\u5426\u5b58\u5728\u8fdb\u7a0b\u3002<\/p>\n
\u8c03\u5ea6\u7a0b\u5e8f\u5728\u9009\u53d6\u6700\u9ad8\u4f18\u5148\u7ea7\u7684\u8fdb\u7a0b\u65f6\uff0c\u9996\u5148\u5229\u7528\u4f18\u5148\u7ea7\u4f4d\u56fe\u4ece\u9ad8\u5230\u4f4e\u627e\u5230\u7b2c\u4e00\u4e2a\u88ab\u8bbe\u7f6e\u7684\u4f4d\uff0c\u8be5\u4f4d\u5bf9\u5e94\u7740\u4e00\u6761\u8fdb\u7a0b\u94fe\u8868\uff0c\u8fd9\u4e2a\u94fe\u8868\u4e2d\u7684\u8fdb\u7a0b\u662f\u5f53\u524d\u7cfb\u7edf\u6240\u6709\u53ef\u8fd0\u884c\u8fdb\u7a0b\u4e2d\u4f18\u5148\u7ea7\u6700\u9ad8\u7684\u3002\u5728\u8be5\u4f18\u5148\u7ea7\u94fe\u8868\u4e2d\u9009\u53d6\u5934\u4e00\u4e2a\u8fdb\u7a0b\uff0c\u5b83\u62e5\u6709\u6700\u9ad8\u7684\u4f18\u5148\u7ea7\uff0c\u5373\u4e3a\u8c03\u5ea6\u7a0b\u5e8f\u9a6c\u4e0a\u8981\u6267\u884c\u7684\u8fdb\u7a0b\u3002\u4e0a\u8ff0\u8fdb\u7a0b\u7684\u9009\u53d6\u8fc7\u7a0b\u53ef\u7528\u4e0b\u8ff0\u4ee3\u7801\u63cf\u8ff0\uff1a<\/p>\n
struct task_struct *prev, *next;\r\nstruct list_head *queue;\r\nstruct prio_array *array;\r\nint idx;\r\n\r\nprev = current;\r\narray = rq->active;\r\nidx = sehed_find_first_bit(array->bitmap);\r\nqueue = array->queue + idx;\r\nnext = list_entry(queue->next, struct task_struct, run_list);\r\nif (prev != next)\r\n\tcontext_switch();<\/pre>\n
sehed_find_first_bit()\u7528\u4e8e\u5728\u4f4d\u56fe\u4e2d\u5feb\u901f\u67e5\u627e\u7b2c\u4e00\u4e2a\u88ab\u8bbe\u7f6e\u7684\u4f4d\u3002\u5982\u679cprev\u548cnext\u4e0d\u662f\u4e00\u4e2a\u8fdb\u7a0b\uff0c\u90a3\u4e48\u6b64\u65f6\u8fdb\u7a0b\u5207\u6362\u5c31\u5f00\u59cb\u6267\u884c\u3002<\/p>\n
\u901a\u8fc7\u4e0a\u8ff0\u7684\u5185\u5bb9\u53ef\u4ee5\u53d1\u73b0\uff0c\u5728\u6052\u5b9a\u7684\u65f6\u95f4\u91cd\u65b0\u5206\u914d\u65f6\u95f4\u7247\u548c\u9009\u62e9\u4e00\u4e2a\u6700\u4f73\u8fdb\u7a0b\u662fQ(1)\u7b97\u6cd5\u7684\u6838\u5fc3\u3002
\n\u53c2\u8003\uff1a<\/strong><\/em><\/p>\n
1.\u6df1\u5165\u7406\u89e3LINUX\u5185\u6838(\u7b2c\u4e09\u7248) \uff1b\uff08\u7f8e\uff09\u535a\u97e6\uff0c\u897f\u65af\u7279 \u8457\uff1b \u9648\u8389\u541b \u5f20\u743c\u58f0 \u5f20\u5b8f\u4f1f\u8bd1\uff1b \u4e2d\u56fd\u7535\u529b\u51fa\u7248\u793e\uff1b<\/strong><\/em><\/p>\n
2.Linux\u5185\u6838\u8bbe\u8ba1\u4e0e\u5b9e\u73b0\uff1b\uff08\u7f8e\uff09\u62c9\u8299\uff08Love\uff0cR.\uff09\u8457\uff0c\u9648\u8389\u541b \u7b49\u8bd1\uff1b\u673a\u68b0\u5de5\u4e1a\u51fa\u7248\u793e\uff1b<\/strong><\/em><\/p>\n","protected":false},"excerpt":{"rendered":"
2.\u6570\u636e\u7ed3\u6784 O(1)\u8c03\u5ea6\u7b97\u6cd5\u901a\u8fc7\u51e0\u4e2a\u6570\u636e\u7ed3\u6784\u53ef\u4ee5\u5de7\u5999\u7684\u5b9e\u73b0\u5e38\u6570\u7ea7\u7684\u590d\u6742\u5ea6\u3002 2.1\u53ef\u8fd0\u884c\u961f\u5217 \u8c03\u5ea6\u7a0b\u5e8f\u6bcf\u6b21\u5728 […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[110],"tags":[134,108,213,214,212],"class_list":["post-2851","post","type-post","status-publish","format-standard","hentry","category-linux","tag-kernel","tag-linux","tag-213","tag-214","tag-212"],"views":10042,"_links":{"self":[{"href":"http:\/\/edsionte.com\/techblog\/wp-json\/wp\/v2\/posts\/2851","targetHints":{"allow":["GET"]}}],"collection":[{"href":"http:\/\/edsionte.com\/techblog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/edsionte.com\/techblog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/edsionte.com\/techblog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/edsionte.com\/techblog\/wp-json\/wp\/v2\/comments?post=2851"}],"version-history":[{"count":0,"href":"http:\/\/edsionte.com\/techblog\/wp-json\/wp\/v2\/posts\/2851\/revisions"}],"wp:attachment":[{"href":"http:\/\/edsionte.com\/techblog\/wp-json\/wp\/v2\/media?parent=2851"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/edsionte.com\/techblog\/wp-json\/wp\/v2\/categories?post=2851"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/edsionte.com\/techblog\/wp-json\/wp\/v2\/tags?post=2851"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}