{"id":10021404,"date":"2026-07-13T23:48:11","date_gmt":"2026-07-13T15:48:11","guid":{"rendered":"https:\/\/itmax.cn\/?p=10021404"},"modified":"2026-07-13T23:48:11","modified_gmt":"2026-07-13T15:48:11","slug":"%e5%ad%97%e8%8a%82java%e4%b8%80%e9%9d%a250%e9%a2%98%ef%bc%9a%e8%80%83%e5%ae%98%e7%9c%9f%e6%ad%a3%e6%83%b3%e5%90%ac%e5%88%b0%e7%9a%84%e7%ad%94%e6%b3%95","status":"publish","type":"post","link":"https:\/\/itmax.cn\/?p=10021404","title":{"rendered":"\u5b57\u8282Java\u4e00\u976250\u9898\uff1a\u8003\u5b98\u771f\u6b63\u60f3\u542c\u5230\u7684\u7b54\u6cd5"},"content":{"rendered":"<p>\u53bb\u5e74\u6211\u5728\u5e2e\u4e00\u4e2a\u670b\u53cb\u505a\u9762\u8bd5 mock\uff0c\u4ed6\u5df2\u7ecf\u80cc\u4e86\u4e09\u904d\u516b\u80a1\u6587\uff0c\u628a ThreadLocal \u7684\u539f\u7406\u3001G1 \u7684 Region \u5212\u5206\u3001MySQL MVCC \u7684\u7248\u672c\u94fe\u8bf4\u5f97\u6eda\u74dc\u70c2\u719f\u3002\u7ed3\u679c\u5b57\u8282\u4e00\u9762\u8fd8\u662f\u6302\u4e86\u3002<\/p>\n<p>\u9762\u8bd5\u5b98\u7684\u53cd\u9988\u53ea\u6709\u4e00\u53e5\u8bdd\uff1a<strong>\u300c\u57fa\u7840\u77e5\u8bc6\u70b9\u80cc\u5f97\u633a\u719f\uff0c\u4f46\u8bf4\u4e0d\u6e05\u695a\u4e3a\u4ec0\u4e48\u8fd9\u6837\u8bbe\u8ba1\uff0c\u4e5f\u6ca1\u6709\u81ea\u5df1\u7684\u5224\u65ad\u3002\u300d<\/strong><\/p>\n<p>\u8fd9\u5c31\u662f\u5b57\u8282\u4e00\u9762\u548c\u5176\u4ed6\u516c\u53f8\u4e00\u9762\u7684\u672c\u8d28\u5dee\u522b\u3002\u5b57\u8282\u4e00\u9762\u4e0d\u662f\u8003\u4f60\u300c\u80cc\u4e86\u591a\u5c11\u300d\uff0c\u8003\u7684\u662f\u4f60<strong>\u300c\u6709\u6ca1\u6709\u60f3\u8fc7\u4e3a\u4ec0\u4e48\u300d<\/strong>\u3002<\/p>\n<p>\u8fd9 50 \u9053\u9898\u662f\u6211\u6574\u7406\u4e86 2025-2026 \u5e74\u5b57\u8282\u540e\u7aef\u4e00\u9762\u7684\u771f\u5b9e\u9762\u7ecf\uff0c\u6309\u516d\u4e2a\u77e5\u8bc6\u57df\u5206\u7c7b\u3002\u6bcf\u9053\u9898\u9664\u4e86\u7ed9\u7b54\u9898\u8981\u70b9\uff0c\u8fd8\u4f1a\u6807\u6ce8\u300c\u8003\u5b98\u60f3\u542c\u5230\u4ec0\u4e48\u89d2\u5ea6\u300d\u2014\u2014\u628a\u95ee\u9898\u653e\u8fdb\u8fd9\u4e2a\u6846\u67b6\u91cc\u56de\u7b54\uff0c\u547d\u4e2d\u7387\u8fdc\u9ad8\u4e8e\u80cc\u4e66\u5f0f\u4f5c\u7b54\u3002<\/p>\n<p><img decoding=\"async\"   referrerpolicy=\"no-referrer\" src=\"https:\/\/segmentfault.com\/img\/remote\/1460000048019313\" alt=\"\u5b57\u8282\u8df3\u52a8Java\u540e\u7aef\u4e00\u9762\u516d\u5927\u6a21\u5757\u8003\u5bdf\u5168\u666f\" title=\"\u5b57\u8282\u8df3\u52a8Java\u540e\u7aef\u4e00\u9762\u516d\u5927\u6a21\u5757\u8003\u5bdf\u5168\u666f\"><\/p>\n<h2>Java \u5e76\u53d1\uff1a\u5b57\u8282\u8003\u5f97\u6700\u6df1\u7684\u6a21\u5757<\/h2>\n<p>\u5927\u591a\u6570\u516c\u53f8\u5e76\u53d1\u8003\u5230\u300csynchronized \u548c ReentrantLock \u7684\u533a\u522b\u300d\u5c31\u7ed3\u675f\u4e86\u3002\u5b57\u8282\u4f1a\u8ffd\u95ee\u9501\u5347\u7ea7\u7684\u5177\u4f53\u6761\u4ef6\u3001AQS \u7684\u7b49\u5f85\u961f\u5217\u5b9e\u73b0\u3001\u4ee5\u53ca ThreadLocal \u5728\u7ebf\u7a0b\u6c60\u573a\u666f\u4e0b\u7684\u5185\u5b58\u6cc4\u6f0f\u662f\u600e\u4e48\u53d1\u751f\u7684\u3002<\/p>\n<p>\u8fd9\u4e2a\u6a21\u5757\u51fa\u73b0\u5728\u8d85\u8fc7 80% \u7684\u5b57\u8282 Java \u4e00\u9762\u4e2d\uff0c\u4e22\u5206\u4e5f\u6700\u591a\u3002<\/p>\n<p><img decoding=\"async\"   referrerpolicy=\"no-referrer\" src=\"https:\/\/segmentfault.com\/img\/remote\/1460000048019314\" alt=\"Java\u5e76\u53d1synchronized vs ReentrantLock vs volatile\u5bf9\u6bd4\" title=\"Java\u5e76\u53d1synchronized vs ReentrantLock vs volatile\u5bf9\u6bd4\" loading=\"lazy\"><\/p>\n<p><strong>Q1. synchronized \u548c ReentrantLock \u7684\u6838\u5fc3\u533a\u522b\u662f\u4ec0\u4e48\uff1f<\/strong><\/p>\n<p>\u8003\u5b98\u60f3\u542c\u7684\u89d2\u5ea6\uff1a\u522b\u53ea\u5217\u529f\u80fd\u5dee\u5f02\uff0c\u8bf4\u51fa\u300c\u4ec0\u4e48\u573a\u666f\u4e0b\u53ea\u80fd\u7528 ReentrantLock\u300d\u3002<\/p>\n<p>\u7b54\u9898\u8981\u70b9\uff1a<\/p>\n<ul>\n<li>synchronized \u662f JVM \u5c42\u7684\u5173\u952e\u5b57\uff0c\u9501\u7684\u83b7\u53d6\/\u91ca\u653e\u7531 JVM \u81ea\u52a8\u7ba1\u7406\uff0c\u4e0d\u53ef\u4e2d\u65ad\u3001\u4e0d\u652f\u6301\u8d85\u65f6\u3001\u4e0d\u80fd\u7ed1\u5b9a\u591a\u4e2a\u6761\u4ef6\u53d8\u91cf<\/li>\n<li>ReentrantLock \u662f AQS \u7684\u5b9e\u73b0\uff0c\u652f\u6301 <code>tryLock(timeout)<\/code> \u8d85\u65f6\u7b49\u5f85\u3001<code>lockInterruptibly()<\/code> \u54cd\u5e94\u4e2d\u65ad\uff0c\u4ee5\u53ca\u591a\u4e2a Condition \u5bf9\u8c61\uff08\u66ff\u4ee3 Object \u7684 wait\/notify \u7ec4\uff0c\u7cbe\u786e\u5524\u9192\u7279\u5b9a\u7ebf\u7a0b\uff09<\/li>\n<li><strong>\u9501\u5347\u7ea7\u662f synchronized \u72ec\u6709\u7684<\/strong>\uff1a\u504f\u5411\u9501 \u2192 \u8f7b\u91cf\u7ea7\u9501 \u2192 \u91cd\u91cf\u7ea7\u9501\uff0c\u7ade\u4e89\u4e0d\u6fc0\u70c8\u65f6\u6027\u80fd\u4e0d\u5dee\uff0c\u751a\u81f3\u4f18\u4e8e ReentrantLock<\/li>\n<li>\u5fc5\u987b\u624b\u52a8 unlock \u7684\u573a\u666f\u4e0b\u7528 ReentrantLock\uff0c\u653e\u5728 finally \u5757<\/li>\n<\/ul>\n<p>\u52a0\u5206\u9879\uff1a\u300cJDK 15 \u4e4b\u540e\u504f\u5411\u9501\u88ab\u9ed8\u8ba4\u5173\u95ed\uff0c\u56e0\u4e3a\u7ef4\u62a4\u6210\u672c\u9ad8\u4e14\u73b0\u4ee3\u7a0b\u5e8f\u7ade\u4e89\u666e\u904d\uff0c\u8fd9\u65f6\u4e24\u8005\u7684\u6027\u80fd\u5dee\u8ddd\u8fdb\u4e00\u6b65\u7f29\u5c0f\u3002\u300d<\/p>\n<p><strong>Q2. synchronized \u7684\u9501\u5347\u7ea7\u8fc7\u7a0b\u662f\u600e\u6837\u7684\uff1f<\/strong><\/p>\n<p>\u8003\u5b98\u60f3\u542c\u7684\u89d2\u5ea6\uff1a\u8bf4\u51fa\u504f\u5411\u9501\u5230\u91cd\u91cf\u7ea7\u9501\u7684\u6761\u4ef6\uff0c\u4e0d\u662f\u53ea\u8bf4\u300c\u4e09\u79cd\u72b6\u6001\u300d\u3002<\/p>\n<p>\u7b54\u9898\u8981\u70b9\uff1a<\/p>\n<ul>\n<li><strong>\u504f\u5411\u9501<\/strong>\uff1a\u5bf9\u8c61\u5934 Mark Word \u8bb0\u5f55\u504f\u5411\u7ebf\u7a0b ID\uff0c\u540c\u4e00\u7ebf\u7a0b\u518d\u6b21\u8fdb\u5165\u65e0\u9700 CAS\uff0c\u51e0\u4e4e\u96f6\u5f00\u9500\u3002\u4f46\u4e00\u65e6\u6709\u7b2c\u4e8c\u4e2a\u7ebf\u7a0b\u7ade\u4e89\uff0c\u5c31\u89e6\u53d1\u504f\u5411\u64a4\u9500\uff08STW\uff09\uff0c\u6210\u672c\u4e0d\u4f4e<\/li>\n<li><strong>\u8f7b\u91cf\u7ea7\u9501<\/strong>\uff1a\u591a\u7ebf\u7a0b\u4ea4\u66ff\u6267\u884c\uff08\u65e0\u771f\u5b9e\u7ade\u4e89\uff09\u65f6\uff0c\u7528\u6808\u5e27\u4e2d\u7684\u9501\u8bb0\u5f55 + Mark Word CAS \u66ff\u6362\uff0c\u907f\u514d\u8fdb\u5185\u6838\u6001\u3002CAS \u5931\u8d25\u4e00\u5b9a\u6b21\u6570\uff08\u81ea\u65cb\uff09\u540e\u5347\u7ea7<\/li>\n<li><strong>\u91cd\u91cf\u7ea7\u9501<\/strong>\uff1a\u5bf9\u5e94 ObjectMonitor\uff0c\u8fdb\u5165\u7b49\u5f85\u961f\u5217\uff0c\u6d89\u53ca\u7ebf\u7a0b\u4e0a\u4e0b\u6587\u5207\u6362\uff0cOS \u5c42\u8c03\u5ea6\uff0c\u5f00\u9500\u6700\u5927<\/li>\n<li>\u9501\u53ea\u80fd\u5347\u7ea7\u4e0d\u80fd\u964d\u7ea7\uff08\u504f\u5411\u9501\u64a4\u9500\u540e\u4e0d\u4f1a\u9000\u56de\uff09<\/li>\n<\/ul>\n<p><strong>Q3. volatile \u7684\u4f5c\u7528\uff0c\u4ee5\u53ca\u5b83\u4e3a\u4ec0\u4e48\u4e0d\u80fd\u4fdd\u8bc1\u539f\u5b50\u6027\uff1f<\/strong><\/p>\n<p>\u8003\u5b98\u60f3\u542c\u7684\u89d2\u5ea6\uff1a\u628a\u53ef\u89c1\u6027\u548c\u6709\u5e8f\u6027\u5206\u5f00\u8bf4\uff0c\u5e76\u7ed9\u51fa\u4e00\u4e2a <code>i++<\/code> \u4e0d\u5b89\u5168\u7684\u5177\u4f53\u4f8b\u5b50\u3002<\/p>\n<p>\u7b54\u9898\u8981\u70b9\uff1a<\/p>\n<ul>\n<li>\u53ef\u89c1\u6027\uff1a\u6bcf\u6b21\u8bfb\u4ece\u4e3b\u5185\u5b58\u8bfb\uff0c\u6bcf\u6b21\u5199\u7acb\u5373\u5237\u5230\u4e3b\u5185\u5b58\uff0c\u7981\u6b62\u5de5\u4f5c\u5185\u5b58\u7f13\u5b58<\/li>\n<li>\u6709\u5e8f\u6027\uff1a\u7981\u6b62\u6307\u4ee4\u91cd\u6392\uff0c\u5e95\u5c42\u662f\u5185\u5b58\u5c4f\u969c\uff08LoadLoad\/StoreStore\/LoadStore\/StoreLoad\uff09<\/li>\n<li>\u4e0d\u4fdd\u8bc1\u539f\u5b50\u6027\uff1a<code>i++<\/code> \u5b9e\u9645\u662f\u4e09\u6761\u5b57\u8282\u7801\u6307\u4ee4\uff08getstatic\u3001iadd\u3001putstatic\uff09\uff0cvolatile \u53ea\u80fd\u4fdd\u8bc1\u6bcf\u6761\u6307\u4ee4\u8bfb\u5199\u7684\u53ef\u89c1\u6027\uff0c\u4f46\u4e09\u6761\u6307\u4ee4\u4e4b\u95f4\u4ecd\u53ef\u80fd\u88ab\u5176\u4ed6\u7ebf\u7a0b\u63d2\u5165<\/li>\n<li>\u5178\u578b\u7528\u6cd5\uff1a\u72b6\u6001\u6807\u5fd7\u4f4d\uff08<code>volatile boolean running<\/code>\uff09\u3001\u53cc\u91cd\u68c0\u67e5\u9501\u4e2d\u9632\u6b62\u534a\u521d\u59cb\u5316\u5bf9\u8c61\u7684\u6307\u4ee4\u91cd\u6392<\/li>\n<\/ul>\n<p><strong>Q4. ThreadLocal \u5185\u5b58\u6cc4\u6f0f\u662f\u600e\u4e48\u53d1\u751f\u7684\uff1f\u600e\u4e48\u907f\u514d\uff1f<\/strong><\/p>\n<p>\u8003\u5b98\u60f3\u542c\u7684\u89d2\u5ea6\uff1a\u8fd9\u662f\u5b57\u8282\u7684\u9ad8\u9891\u8ffd\u95ee\u9898\uff0c\u5fc5\u987b\u8bf4\u5230 WeakReference \u548c\u7ebf\u7a0b\u6c60\u7684\u5173\u7cfb\u3002<\/p>\n<p>\u7b54\u9898\u8981\u70b9\uff1a<\/p>\n<ul>\n<li><code>ThreadLocalMap<\/code> \u7684 key \u662f <code>WeakReference&lt;ThreadLocal&gt;<\/code>\uff0cvalue \u662f\u5f3a\u5f15\u7528<\/li>\n<li>\u5f53 ThreadLocal \u5b9e\u4f8b\u6ca1\u6709\u5916\u90e8\u5f3a\u5f15\u7528\u65f6\uff0ckey \u88ab GC \u56de\u6536\u53d8\u4e3a null\uff0c\u4f46 value \u4ecd\u7136\u5b58\u6d3b\u5728 Entry \u4e2d<\/li>\n<li>\u666e\u901a\u7ebf\u7a0b\u7528\u5b8c\u9500\u6bc1\u95ee\u9898\u4e0d\u5927\uff1b\u7ebf\u7a0b\u6c60\u91cc\u7ebf\u7a0b\u4e0d\u9500\u6bc1\uff0c\u8fd9\u4e9b null-key \u7684 Entry \u8d8a\u79ef\u8d8a\u591a\uff0c\u6700\u7ec8 OOM<\/li>\n<li><strong>\u89e3\u6cd5<\/strong>\uff1a\u6bcf\u6b21\u7528\u5b8c\u8c03 <code>threadLocal.remove()<\/code>\uff0c\u653e\u5728 finally \u5757<\/li>\n<\/ul>\n<p>\u52a0\u5206\u9879\uff1a\u300cSpring \u6846\u67b6\u7684 <code>TransactionSynchronizationManager<\/code> \u7528\u7684\u5c31\u662f ThreadLocal\uff0c\u5b83\u5728 <code>cleanupTransactionInfo()<\/code> \u91cc\u6709 remove\uff0c\u8fd9\u662f\u89c4\u8303\u505a\u6cd5\u3002\u300d<\/p>\n<p><strong>Q5. AQS \u7684\u6838\u5fc3\u5b9e\u73b0\u539f\u7406\u662f\u4ec0\u4e48\uff1f<\/strong><\/p>\n<p>\u8003\u5b98\u60f3\u542c\u7684\u89d2\u5ea6\uff1a\u8bf4\u51fa state \u53d8\u91cf + CLH \u7b49\u5f85\u961f\u5217 + <code>tryAcquire<\/code> \u6a21\u677f\u65b9\u6cd5\u7684\u4e09\u89d2\u5173\u7cfb\u3002<\/p>\n<p>\u7b54\u9898\u8981\u70b9\uff1a<\/p>\n<ul>\n<li>AQS \u5185\u90e8\u6709\u4e09\u4e2a\u6838\u5fc3\uff1a<code>volatile int state<\/code>\uff08\u8868\u793a\u9501\/\u8d44\u6e90\u72b6\u6001\uff09\u3001\u5f53\u524d\u6301\u9501\u7ebf\u7a0b\u3001FIFO \u7b49\u5f85\u961f\u5217\uff08CLH \u53d8\u4f53\uff09<\/li>\n<li>\u52a0\u9501\u5931\u8d25\u65f6\uff0c\u7ebf\u7a0b\u88ab\u5c01\u88c5\u4e3a Node \u8fdb\u5165\u961f\u5217\uff0c\u901a\u8fc7 <code>LockSupport.park<\/code> \u6302\u8d77<\/li>\n<li>\u89e3\u9501\u65f6\uff0c\u4fee\u6539 state \u5e76\u5524\u9192\u961f\u5934\u8282\u70b9\u7684\u540e\u7ee7\u7ebf\u7a0b\uff08<code>LockSupport.unpark<\/code>\uff09<\/li>\n<li><code>ReentrantLock<\/code>\u3001<code>Semaphore<\/code>\u3001<code>CountDownLatch<\/code> \u90fd\u662f AQS \u7684\u5b50\u7c7b\uff0c\u53ea\u9700\u5b9e\u73b0 <code>tryAcquire\/tryRelease<\/code>\uff08\u72ec\u5360\uff09\u6216 <code>tryAcquireShared\/tryReleaseShared<\/code>\uff08\u5171\u4eab\uff09<\/li>\n<\/ul>\n<p><strong>Q6. ConcurrentHashMap \u7684\u7ebf\u7a0b\u5b89\u5168\u662f\u600e\u4e48\u5b9e\u73b0\u7684\uff1fJDK 7 \u548c JDK 8 \u7684\u5dee\u5f02\uff1f<\/strong><\/p>\n<p>\u7b54\u9898\u8981\u70b9\uff1a<\/p>\n<ul>\n<li>JDK 7\uff1a\u5206\u6bb5\u9501\uff08Segment\uff09\uff0c\u6bcf\u4e2a Segment \u7ee7\u627f ReentrantLock\uff0c\u9501\u7c92\u5ea6\u662f\u6574\u4e2a\u6876\u6570\u7ec4\u6bb5<\/li>\n<li>JDK 8\uff1a\u5f7b\u5e95\u91cd\u5199\u3002\u7528 <code>Node[] table<\/code> \u4ee3\u66ff Segment\uff0c\u9501\u7c92\u5ea6\u7ec6\u5316\u5230\u6bcf\u4e2a\u6876\u7684\u5934\u8282\u70b9\uff08<code>synchronized<\/code> + CAS\uff09\u3002\u7a7a\u6876\u5199\u5165\u7528 CAS\uff0c\u53d1\u751f\u78b0\u649e\u624d\u52a0 synchronized<\/li>\n<li>\u6269\u5bb9\uff1a\u5f15\u5165 ForwardingNode \u6807\u8bb0\u5df2\u8fc1\u79fb\u7684\u6876\uff0c\u591a\u7ebf\u7a0b\u534f\u540c\u8fc1\u79fb<\/li>\n<li><code>size()<\/code> \u65b9\u6cd5\u7528 <code>CounterCell<\/code> \u5206\u6563\u8ba1\u6570\uff0c\u907f\u514d\u8ba1\u6570\u5668\u672c\u8eab\u6210\u4e3a\u7ade\u4e89\u74f6\u9888<\/li>\n<\/ul>\n<p><strong>Q7. \u7ebf\u7a0b\u6c60\u7684\u6838\u5fc3\u53c2\u6570\uff0c\u4ee5\u53ca\u4efb\u52a1\u63d0\u4ea4\u7684\u5b8c\u6574\u6d41\u7a0b\uff1f<\/strong><\/p>\n<p>\u8003\u5b98\u60f3\u542c\u7684\u89d2\u5ea6\uff1a\u5fc5\u987b\u8bf4\u51fa\u62d2\u7edd\u7b56\u7565\u89e6\u53d1\u7684\u5177\u4f53\u6761\u4ef6\uff0c\u5f88\u591a\u4eba\u5728\u8fd9\u91cc\u7b54\u9519\u3002<\/p>\n<p>\u7b54\u9898\u8981\u70b9\uff1a<\/p>\n<ul>\n<li>7 \u4e2a\u6838\u5fc3\u53c2\u6570\uff1a<code>corePoolSize<\/code>\u3001<code>maximumPoolSize<\/code>\u3001<code>keepAliveTime<\/code>\u3001<code>unit<\/code>\u3001<code>workQueue<\/code>\u3001<code>threadFactory<\/code>\u3001<code>handler<\/code><\/li>\n<li>\u63d0\u4ea4\u6d41\u7a0b\uff1a\u7ebf\u7a0b\u6570 &lt; corePoolSize \u2192 \u521b\u5efa\u6838\u5fc3\u7ebf\u7a0b\uff1b&gt;= corePoolSize \u2192 \u5165\u961f\uff1b\u961f\u5217\u6ee1\u4e14\u7ebf\u7a0b\u6570 &lt; maximumPoolSize \u2192 \u521b\u5efa\u975e\u6838\u5fc3\u7ebf\u7a0b\uff1b\u961f\u5217\u6ee1\u4e14\u7ebf\u7a0b\u6570 = maximumPoolSize \u2192 \u89e6\u53d1\u62d2\u7edd\u7b56\u7565<\/li>\n<li>\u6ce8\u610f\uff1a<strong>\u961f\u5217\u6ee1\u624d\u4f1a\u521b\u5efa\u975e\u6838\u5fc3\u7ebf\u7a0b<\/strong>\uff0c\u4e0d\u662f\u5148\u62c9\u6ee1\u7ebf\u7a0b\u6570\u518d\u5165\u961f<\/li>\n<li>4 \u79cd\u62d2\u7edd\u7b56\u7565\uff1a<code>AbortPolicy<\/code>\uff08\u629b\u5f02\u5e38\uff0c\u9ed8\u8ba4\uff09\u3001<code>CallerRunsPolicy<\/code>\uff08\u8c03\u7528\u8005\u7ebf\u7a0b\u6267\u884c\uff09\u3001<code>DiscardPolicy<\/code>\uff08\u9759\u9ed8\u4e22\u5f03\uff09\u3001<code>DiscardOldestPolicy<\/code>\uff08\u4e22\u961f\u5934\u6700\u8001\u7684\u4efb\u52a1\uff09<\/li>\n<\/ul>\n<p>\u52a0\u5206\u9879\uff1a\u300c\u751f\u4ea7\u91cc\u8981\u7528 <code>CallerRunsPolicy<\/code> \u505a\u53cd\u538b\uff0c\u907f\u514d\u4efb\u52a1\u88ab\u9759\u9ed8\u4e22\u6389\u3002\u300d<\/p>\n<p><strong>Q8. happens-before \u539f\u5219\u662f\u4ec0\u4e48\uff1f<\/strong><\/p>\n<p>\u7b54\u9898\u8981\u70b9\uff1a<\/p>\n<ul>\n<li>JMM \u5bf9\u5185\u5b58\u53ef\u89c1\u6027\u7684\u4fdd\u8bc1\u89c4\u5219\uff0c\u4e0d\u9700\u8981\u6bcf\u6b21\u90fd\u7528 synchronized\uff0c\u53ea\u8981\u6ee1\u8db3 happens-before \u5173\u7cfb\uff0c\u524d\u4e00\u4e2a\u64cd\u4f5c\u7684\u7ed3\u679c\u5bf9\u540e\u4e00\u4e2a\u64cd\u4f5c\u53ef\u89c1<\/li>\n<li>\u5e38\u7528\u7684\uff1a\u7a0b\u5e8f\u987a\u5e8f\u89c4\u5219\u3001\u76d1\u89c6\u5668\u9501\u89c4\u5219\uff08unlock happens-before \u968f\u540e\u7684 lock\uff09\u3001volatile \u53d8\u91cf\u89c4\u5219\u3001\u7ebf\u7a0b\u542f\u52a8\u89c4\u5219\u3001\u7ebf\u7a0b\u7ec8\u6b62\u89c4\u5219<\/li>\n<li>\u6838\u5fc3\u610f\u4e49\uff1ahappens-before \u662f\u7a0b\u5e8f\u5458\u548c JMM \u4e4b\u95f4\u7684\u5951\u7ea6\uff0cJMM \u627f\u8bfa\u5728\u6ee1\u8db3\u8fd9\u4e9b\u89c4\u5219\u65f6\u4fdd\u8bc1\u53ef\u89c1\u6027<\/li>\n<\/ul>\n<p><strong>Q9. \u4ec0\u4e48\u662f\u4f2a\u5171\u4eab\uff08False Sharing\uff09\uff1f\u5982\u4f55\u89e3\u51b3\uff1f<\/strong><\/p>\n<p>\u7b54\u9898\u8981\u70b9\uff1a<\/p>\n<ul>\n<li>CPU \u4ee5 Cache Line\uff08\u901a\u5e38 64 \u5b57\u8282\uff09\u4e3a\u5355\u4f4d\u8bfb\u5199\u7f13\u5b58\uff0c\u4e24\u4e2a\u53d8\u91cf\u5982\u679c\u5728\u540c\u4e00 Cache Line\uff0c\u4e00\u4e2a\u7ebf\u7a0b\u4fee\u6539\u53d8\u91cf A\uff0c\u53e6\u4e00\u4e2a\u7ebf\u7a0b\u7684\u53d8\u91cf B \u6240\u5728\u7f13\u5b58\u884c\u4e5f\u4f1a\u5931\u6548\uff0c\u5373\u4f7f B \u6ca1\u88ab\u4fee\u6539<\/li>\n<li>\u89e3\u51b3\u65b9\u6848\uff1a\u5b57\u8282\u586b\u5145\uff08Padding\uff09\uff0c\u8ba9\u4e24\u4e2a\u70ed\u70b9\u53d8\u91cf\u5206\u522b\u72ec\u5360\u4e00\u4e2a Cache Line<\/li>\n<li>Java 7+ \u7684 <code>@Contended<\/code> \u6ce8\u89e3\uff08\u9700 <code>-XX:-RestrictContended<\/code>\uff09\u81ea\u52a8\u586b\u5145\uff0c<code>LongAdder<\/code>\u3001<code>ConcurrentHashMap.CounterCell<\/code> \u90fd\u7528\u4e86\u8fd9\u4e2a\u6280\u672f<\/li>\n<\/ul>\n<p><strong>Q10. CompletableFuture \u548c Future \u7684\u533a\u522b\uff1f<\/strong><\/p>\n<p>\u7b54\u9898\u8981\u70b9\uff1a<\/p>\n<ul>\n<li><code>Future.get()<\/code> \u662f\u963b\u585e\u8c03\u7528\uff0c\u6ca1\u6cd5\u94fe\u5f0f\u7ec4\u5408\u591a\u4e2a\u5f02\u6b65\u4efb\u52a1<\/li>\n<li><code>CompletableFuture<\/code> \u5b9e\u73b0\u4e86 <code>CompletionStage<\/code>\uff0c\u652f\u6301 <code>thenApply<\/code>\uff08\u540c\u6b65\u8f6c\u6362\uff09\u3001<code>thenCompose<\/code>\uff08\u5f02\u6b65\u94fe\u5f0f\uff09\u3001<code>thenCombine<\/code>\uff08\u5408\u5e76\u4e24\u4e2a\u7ed3\u679c\uff09\u3001<code>exceptionally<\/code>\uff08\u5f02\u5e38\u5904\u7406\uff09<\/li>\n<li>\u9ed8\u8ba4\u7528 <code>ForkJoinPool.commonPool()<\/code> \u6267\u884c\uff0c\u4e5f\u53ef\u4ee5\u4f20\u5165\u81ea\u5b9a\u4e49\u7ebf\u7a0b\u6c60\uff08\u63a8\u8350\uff0c\u907f\u514d\u516c\u5171\u6c60\u88ab\u5360\u6ee1\uff09<\/li>\n<li>\u9002\u5408\u573a\u666f\uff1a\u591a\u4e2a RPC \u5e76\u884c\u8c03\u7528\u540e\u5408\u5e76\u7ed3\u679c\uff0c\u53d6\u4ee3 <code>CountDownLatch<\/code> + <code>Future.get()<\/code> \u7684\u7ec4\u5408<\/li>\n<\/ul>\n<h2>JVM\uff1a\u5b57\u8282\u504f\u7231\u8ffd\u95ee GC \u7ec6\u8282<\/h2>\n<p>JVM \u6a21\u5757\u5b57\u8282\u901a\u5e38\u4e0d\u95ee\u300c\u5806\u7ed3\u6784\u662f\u4ec0\u4e48\u300d\u8fd9\u79cd\u5165\u95e8\u9898\uff0c\u800c\u662f\u95ee\u300c\u4f60\u4eec\u7ebf\u4e0a Full GC \u600e\u4e48\u6392\u67e5\u300d\u300cG1 \u4ec0\u4e48\u65f6\u5019\u4f1a\u9000\u5316\u4e3a Full GC\u300d\u300c\u7c7b\u52a0\u8f7d\u4ec0\u4e48\u60c5\u51b5\u4e0b\u4f1a\u7834\u574f\u53cc\u4eb2\u59d4\u6d3e\u300d\u3002<\/p>\n<p><strong>Q11. G1 GC \u7684\u5de5\u4f5c\u539f\u7406\uff0c\u4ee5\u53ca\u5b83\u76f8\u6bd4 CMS \u7684\u4f18\u52bf\uff1f<\/strong><\/p>\n<p>\u8003\u5b98\u60f3\u542c\u7684\u89d2\u5ea6\uff1a\u8bf4\u51fa Region \u8bbe\u8ba1\u7684\u6838\u5fc3\u52a8\u673a\u2014\u2014\u53ef\u9884\u6d4b\u7684\u505c\u987f\u65f6\u95f4\u3002<\/p>\n<p>\u7b54\u9898\u8981\u70b9\uff1a<\/p>\n<ul>\n<li>G1 \u628a\u5806\u5212\u5206\u4e3a\u5927\u5c0f\u76f8\u7b49\u7684 Region\uff08\u9ed8\u8ba4 2MB\uff09\uff0c\u4e0d\u56fa\u5b9a\u6bcf\u4e2a Region \u7684\u89d2\u8272\uff08Eden\/Survivor\/Old \u53ef\u4ee5\u52a8\u6001\u53d8\u5316\uff09<\/li>\n<li>\u4f18\u5148\u56de\u6536\u300c\u5783\u573e\u5360\u6bd4\u9ad8\u7684 Region\u300d\uff08Garbage First\uff09\uff0c\u5728\u7528\u6237\u8bbe\u5b9a\u7684\u505c\u987f\u65f6\u95f4\u76ee\u6807\u5185\u5c3d\u91cf\u591a\u56de\u6536<\/li>\n<li>\u6df7\u5408\u56de\u6536\uff08Mixed GC\uff09\uff1a\u5e74\u8f7b\u4ee3 + \u90e8\u5206\u8001\u5e74\u4ee3 Region \u4e00\u8d77\u56de\u6536\uff0c\u907f\u514d CMS \u7684\u5168\u8001\u5e74\u4ee3\u56de\u6536<\/li>\n<li>CMS \u7684\u95ee\u9898\uff1a\u788e\u7247\u5316\uff08\u6807\u8bb0-\u6e05\u9664\uff09\u3001\u65e0\u6cd5\u5e94\u5bf9\u6d6e\u52a8\u5783\u573e\u65f6\u4f1a\u9000\u5316\u4e3a Serial Old\uff1bG1 \u4f7f\u7528\u6807\u8bb0-\u6574\u7406\uff0c\u65e0\u788e\u7247<\/li>\n<\/ul>\n<p>\u52a0\u5206\u9879\uff1a\u300cRegion \u5185\u90e8\u5bf9\u8c61\u8de8 Region \u5f15\u7528\u9760 Remembered Set \u7ef4\u62a4\uff0c\u8fd9\u662f G1 \u5199\u5c4f\u969c\u7684\u4ee3\u4ef7\uff0c\u5185\u5b58\u5360\u7528\u901a\u5e38\u6bd4 CMS \u591a 10-20%\u3002\u300d<\/p>\n<p><strong>Q12. Minor GC\u3001Major GC\u3001Full GC \u7684\u89e6\u53d1\u6761\u4ef6\u5206\u522b\u662f\u4ec0\u4e48\uff1f<\/strong><\/p>\n<p>\u7b54\u9898\u8981\u70b9\uff1a<\/p>\n<ul>\n<li>Minor GC\uff1aEden \u533a\u6ee1\u65f6\u89e6\u53d1\uff0c\u56de\u6536\u5e74\u8f7b\u4ee3\uff08Eden + Survivor\uff09\uff0c\u901f\u5ea6\u5feb<\/li>\n<li>Major GC\uff1a\u901a\u5e38\u6307\u8001\u5e74\u4ee3 GC\uff0cG1 \u91cc\u53eb Mixed GC\uff0cCMS \u53eb Old GC<\/li>\n<li>Full GC\uff1a\u56de\u6536\u6574\u4e2a\u5806\uff08\u5e74\u8f7b\u4ee3 + \u8001\u5e74\u4ee3 + \u65b9\u6cd5\u533a\uff09\uff0c\u89e6\u53d1\u6761\u4ef6\uff1a\u8c03\u7528 <code>System.gc()<\/code>\uff1b\u8001\u5e74\u4ee3\u7a7a\u95f4\u4e0d\u8db3\uff1b\u65b9\u6cd5\u533a\u7a7a\u95f4\u4e0d\u8db3\uff1bMinor GC \u540e\u664b\u5347\u5230\u8001\u5e74\u4ee3\u7684\u5bf9\u8c61\u8d85\u8fc7\u8001\u5e74\u4ee3\u5269\u4f59\u7a7a\u95f4\uff08\u664b\u5347\u62c5\u4fdd\u5931\u8d25\uff09<\/li>\n<li>G1 \u9000\u5316\u4e3a Full GC\uff1a\u5e76\u53d1\u6807\u8bb0\u8ddf\u4e0d\u4e0a\u5206\u914d\u901f\u5ea6\uff0c\u6216 Evacuation Failure\uff08\u758f\u6563\u5931\u8d25\uff0cRegion \u4e0d\u591f\u7528\uff09<\/li>\n<\/ul>\n<p><strong>Q13. \u7c7b\u52a0\u8f7d\u7684\u53cc\u4eb2\u59d4\u6d3e\u673a\u5236\uff0c\u54ea\u4e9b\u60c5\u51b5\u4e0b\u4f1a\u7834\u574f\u5b83\uff1f<\/strong><\/p>\n<p>\u8003\u5b98\u60f3\u542c\u7684\u89d2\u5ea6\uff1a\u7ed9\u51fa\u771f\u5b9e\u573a\u666f\uff0c\u4e0d\u662f\u80cc\u5b9a\u4e49\u3002<\/p>\n<p>\u7b54\u9898\u8981\u70b9\uff1a<\/p>\n<ul>\n<li>\u53cc\u4eb2\u59d4\u6d3e\uff1a\u52a0\u8f7d\u7c7b\u5148\u59d4\u6d3e\u7236\u7c7b\u52a0\u8f7d\u5668\uff0c\u7236\u7c7b\u627e\u4e0d\u5230\u624d\u81ea\u5df1\u52a0\u8f7d\uff0c\u4fdd\u8bc1\u6838\u5fc3\u7c7b\u5e93\u4e0d\u88ab\u8986\u76d6<\/li>\n<li>\u7834\u574f\u573a\u666f\u4e00\uff1aJDBC\u3002<code>DriverManager<\/code> \u5728 Bootstrap ClassLoader \u91cc\uff0c\u4f46\u9700\u8981\u52a0\u8f7d\u5404\u5382\u5546\u7684 Driver \u5b9e\u73b0\uff08\u5728\u5e94\u7528 classpath\uff09\uff0c\u56e0\u6b64\u7528\u4e86\u7ebf\u7a0b\u4e0a\u4e0b\u6587\u7c7b\u52a0\u8f7d\u5668\uff08<code>Thread.getContextClassLoader()<\/code>\uff09\u53cd\u5411\u59d4\u6d3e<\/li>\n<li>\u7834\u574f\u573a\u666f\u4e8c\uff1aTomcat\u3002\u6bcf\u4e2a Web App \u6709\u72ec\u7acb ClassLoader\uff0c\u53ef\u4ee5\u52a0\u8f7d\u540c\u540d\u4f46\u4e0d\u540c\u7248\u672c\u7684\u7c7b\uff08\u5982 Spring 3 \u548c Spring 4 \u5e76\u5b58\uff09\uff0c\u6545\u610f\u6253\u7834\u9694\u79bb<\/li>\n<li>\u7834\u574f\u573a\u666f\u4e09\uff1aOSGi\u3001\u70ed\u90e8\u7f72\u573a\u666f\uff0c\u9700\u8981\u52a8\u6001\u66ff\u6362\u7c7b<\/li>\n<\/ul>\n<p><strong>Q14. JVM \u7684\u5185\u5b58\u533a\u57df\u5212\u5206\uff0c\u54ea\u4e9b\u533a\u57df\u53ef\u80fd OOM\uff1f<\/strong><\/p>\n<p>\u7b54\u9898\u8981\u70b9\uff1a<\/p>\n<ul>\n<li>\u7ebf\u7a0b\u79c1\u6709\uff1a\u7a0b\u5e8f\u8ba1\u6570\u5668\uff08\u552f\u4e00\u4e0d\u4f1a OOM\uff09\u3001\u865a\u62df\u673a\u6808\uff08StackOverflowError \/ OOM\uff09\u3001\u672c\u5730\u65b9\u6cd5\u6808<\/li>\n<li>\u7ebf\u7a0b\u5171\u4eab\uff1a\u5806\uff08Java \u5bf9\u8c61\uff0c\u6700\u5e38\u89c1\u7684 OOM\uff09\u3001\u65b9\u6cd5\u533a\/\u5143\u7a7a\u95f4\uff08\u5b58\u7c7b\u5143\u4fe1\u606f\uff0c\u5143\u7a7a\u95f4 OOM \u901a\u5e38\u56e0\u4e3a\u52a8\u6001\u751f\u6210\u5927\u91cf\u7c7b\uff0c\u5982 CGLib\uff09<\/li>\n<li>\u76f4\u63a5\u5185\u5b58\uff1aNIO ByteBuffer \u76f4\u63a5\u5185\u5b58\u4e0d\u53d7\u5806\u7ba1\u7406\uff0cUnsafe \u5206\u914d\uff0cOOM \u8868\u73b0\u4e3a\u300cOutOfMemoryError: Direct buffer memory\u300d<\/li>\n<\/ul>\n<p><strong>Q15. \u5982\u4f55\u5b9a\u4f4d\u4e00\u6b21\u751f\u4ea7 Full GC \u9891\u7e41\u7684\u95ee\u9898\uff1f<\/strong><\/p>\n<p>\u8003\u5b98\u60f3\u542c\u7684\u89d2\u5ea6\uff1a\u8bf4\u51fa\u6392\u67e5\u5de5\u5177\u94fe\uff0c\u800c\u4e0d\u53ea\u662f\u8bf4\u300c\u770b GC \u65e5\u5fd7\u300d\u3002<\/p>\n<p>\u7b54\u9898\u8981\u70b9\uff1a<\/p>\n<ol>\n<li>\u5f00\u542f GC \u65e5\u5fd7\uff1a<code>-Xlog:gc*:file=gc.log:time<\/code>\uff08JDK 9+\uff09\uff0c\u89c2\u5bdf Full GC \u9891\u7387\u548c\u6bcf\u6b21\u505c\u987f\u65f6\u95f4<\/li>\n<li>\u7528 <code>jmap -histo:live &lt;pid&gt;<\/code> \u770b\u5b58\u6d3b\u5bf9\u8c61\u5206\u5e03\uff0c\u627e\u6392\u540d\u9760\u524d\u7684\u5927\u5bf9\u8c61<\/li>\n<li><code>jmap -dump:format=b,file=heap.hprof &lt;pid&gt;<\/code> dump \u5806\uff0cMAT \u5206\u6790 Retention Heap\uff0c\u627e\u5f15\u7528\u94fe<\/li>\n<li>\u5e38\u89c1\u6839\u56e0\uff1a\u5185\u5b58\u6cc4\u6f0f\uff08\u7f13\u5b58 Map \u6ca1\u6709\u8fc7\u671f\u7b56\u7565\uff09\u3001\u5927\u5bf9\u8c61\u76f4\u63a5\u8fdb\u8001\u5e74\u4ee3\uff08-XX:PretenureSizeThreshold\uff09\u3001\u5143\u7a7a\u95f4\u4e0d\u8db3\uff08\u52a8\u6001\u4ee3\u7406 + \u7c7b\u5378\u8f7d\u95ee\u9898\uff09<\/li>\n<\/ol>\n<p><strong>Q16. ZGC \u7684\u6838\u5fc3\u7279\u70b9\u662f\u4ec0\u4e48\uff1f\u9002\u5408\u4ec0\u4e48\u573a\u666f\uff1f<\/strong><\/p>\n<p>\u7b54\u9898\u8981\u70b9\uff1a<\/p>\n<ul>\n<li>\u76ee\u6807\uff1a\u505c\u987f\u65f6\u95f4\u4e0d\u8d85\u8fc7 10ms\uff0c\u4e14\u4e0e\u5806\u5927\u5c0f\u65e0\u5173\uff08G1 \u7684\u505c\u987f\u968f\u5806\u5927\u5c0f\u589e\u957f\uff09<\/li>\n<li>\u6838\u5fc3\u6280\u672f\uff1a\u7740\u8272\u6307\u9488\uff08Colored Pointers\uff09+ \u8bfb\u5c4f\u969c\uff0c\u5728\u5e76\u53d1\u9636\u6bb5\u5b8c\u6210\u5bf9\u8c61\u79fb\u52a8\uff0c\u4e0d\u9700\u8981 STW<\/li>\n<li>JDK 15 \u6b63\u5f0f\u751f\u4ea7\u53ef\u7528\uff0cJDK 21 \u5f15\u5165\u5206\u4ee3 ZGC\uff0c\u8fdb\u4e00\u6b65\u964d\u4f4e\u5185\u5b58\u5360\u7528<\/li>\n<li>\u9002\u5408\u573a\u666f\uff1a\u5927\u5806\uff08&gt;32GB\uff09+ \u5ef6\u8fdf\u654f\u611f\uff08\u91d1\u878d\u4ea4\u6613\u3001\u5b9e\u65f6\u63a8\u8350\uff09\uff0c\u4ee3\u4ef7\u662f CPU \u5f00\u9500\u9ad8\u4e8e G1 \u7ea6 5-10%<\/li>\n<\/ul>\n<p><strong>Q17. \u4ec0\u4e48\u60c5\u51b5\u4e0b\u5bf9\u8c61\u4f1a\u76f4\u63a5\u8fdb\u5165\u8001\u5e74\u4ee3\uff1f<\/strong><\/p>\n<p>\u7b54\u9898\u8981\u70b9\uff1a<\/p>\n<ul>\n<li>\u5927\u5bf9\u8c61\uff08<code>-XX:PretenureSizeThreshold<\/code>\uff0c\u9ed8\u8ba4\u5173\u95ed\uff0c\u8bbe\u7f6e\u9608\u503c\u540e\u8d85\u8fc7\u8be5\u5927\u5c0f\u76f4\u63a5\u8fdb\u8001\u5e74\u4ee3\uff09<\/li>\n<li>\u957f\u671f\u5b58\u6d3b\u5bf9\u8c61\uff08\u9ed8\u8ba4 15 \u6b21 Minor GC \u540e\uff0c\u5e74\u9f84\u9608\u503c <code>-XX:MaxTenuringThreshold<\/code>\uff09<\/li>\n<li>\u52a8\u6001\u5e74\u9f84\u5224\u65ad\uff1aSurvivor \u533a\u540c\u9f84\u5bf9\u8c61\u5360 Survivor \u7a7a\u95f4 50% \u4ee5\u4e0a\uff0c\u76f4\u63a5\u664b\u5347\uff08\u4e0d\u9700\u8981\u7b49\u5230 15 \u6b21\uff09<\/li>\n<li>\u664b\u5347\u62c5\u4fdd\u5931\u8d25\uff1aMinor GC \u524d\u68c0\u67e5\u8001\u5e74\u4ee3\u8fde\u7eed\u7a7a\u95f4\u662f\u5426\u8db3\u4ee5\u5bb9\u7eb3\u6700\u8fd1\u51e0\u6b21\u5e73\u5747\u664b\u5347\u91cf\uff0c\u4e0d\u591f\u5219 Full GC<\/li>\n<\/ul>\n<p><strong>Q18. \u4ec0\u4e48\u662f TLAB\uff1f\u4e3a\u4ec0\u4e48\u9700\u8981\u5b83\uff1f<\/strong><\/p>\n<p>\u7b54\u9898\u8981\u70b9\uff1a<\/p>\n<ul>\n<li>Thread Local Allocation Buffer\uff0c\u6bcf\u4e2a\u7ebf\u7a0b\u5728 Eden \u533a\u72ec\u5360\u7684\u4e00\u5c0f\u5757\u5185\u5b58\u7528\u4e8e\u5bf9\u8c61\u5206\u914d<\/li>\n<li>\u907f\u514d\u591a\u7ebf\u7a0b\u5206\u914d\u5bf9\u8c61\u65f6\u5728 Eden \u4e0a CAS \u7ade\u4e89\uff08\u867d\u7136 CAS \u5355\u6b21\u5feb\uff0c\u4f46\u9ad8\u9891\u5206\u914d\u4e0b\u7ade\u4e89\u660e\u663e\uff09<\/li>\n<li>TLAB \u7528\u5b8c\u4e86\u518d\u7533\u8bf7\u4e00\u5757\u65b0\u7684\uff0c\u7533\u8bf7\u65f6\u9700\u8981\u5168\u5c40\u9501\uff0c\u4f46\u9891\u7387\u4f4e<\/li>\n<li>\u5927\u5bf9\u8c61\u76f4\u63a5\u5728 Eden \u4e0a CAS \u5206\u914d\uff08\u7ed5\u8fc7 TLAB\uff09<\/li>\n<\/ul>\n<h2>MySQL\uff1a\u7d22\u5f15\u548c\u4e8b\u52a1\u5fc5\u8003\uff0cInnoDB \u5185\u90e8\u673a\u5236\u770b\u8fd0\u6c14<\/h2>\n<p>\u5b57\u8282 MySQL \u6a21\u5757\u901a\u5e38\u5148\u95ee\u7d22\u5f15\uff0c\u518d\u8ffd\u95ee\u4e8b\u52a1\u548c\u9501\uff0c\u6700\u540e\u770b\u60c5\u51b5\u804a binlog\/redo log\u3002\u6700\u8fd1\u4e24\u5e74\u51fa\u73b0\u4e86\u300c\u5206\u5e93\u5206\u8868\u7684\u8de8\u5e93\u67e5\u8be2\u600e\u4e48\u505a\u300d\u7684\u573a\u666f\u9898\uff0c\u9700\u8981\u6709\u5177\u4f53\u65b9\u6848\u3002<\/p>\n<p><strong>Q19. MySQL \u4e3a\u4ec0\u4e48\u7528 B+ \u6811\u505a\u7d22\u5f15\uff0c\u800c\u4e0d\u662f B \u6811\u6216\u54c8\u5e0c\u8868\uff1f<\/strong><\/p>\n<p>\u8003\u5b98\u60f3\u542c\u7684\u89d2\u5ea6\uff1a\u4ece\u78c1\u76d8 I\/O \u7684\u89c6\u89d2\u89e3\u91ca\uff0c\u800c\u4e0d\u53ea\u662f\u8bf4\u300cB+ \u6811\u53f6\u5b50\u8282\u70b9\u6709\u94fe\u8868\u300d\u3002<\/p>\n<p>\u7b54\u9898\u8981\u70b9\uff1a<\/p>\n<ul>\n<li>B \u6811 vs B+ \u6811\uff1aB \u6811\u7684\u975e\u53f6\u8282\u70b9\u4e5f\u5b58\u6570\u636e\uff0c\u5bfc\u81f4\u6bcf\u4e2a\u8282\u70b9\u80fd\u5b58\u7684 key \u6570\u53d8\u5c11\uff0c\u6811\u9ad8\u66f4\u9ad8\uff0c\u78c1\u76d8 I\/O \u6b21\u6570\u66f4\u591a\uff1bB+ \u6811\u975e\u53f6\u8282\u70b9\u53ea\u5b58 key\uff0c4KB \u9875\u9762\u80fd\u5b58\u66f4\u591a key\uff0c\u6811\u9ad8\u901a\u5e38\u53ea\u6709 3-4 \u5c42\uff0810 \u4ebf\u884c\u6570\u636e\u6811\u9ad8\u7ea6 4\uff09<\/li>\n<li>B+ \u6811\u53f6\u8282\u70b9\u7528\u94fe\u8868\u76f8\u8fde\uff0c\u652f\u6301\u9ad8\u6548\u7684\u8303\u56f4\u67e5\u8be2\uff08<code>BETWEEN<\/code>\u3001<code>ORDER BY<\/code>\uff09\uff0cB \u6811\u505a\u4e0d\u5230<\/li>\n<li>\u54c8\u5e0c\u8868\u4e0d\u652f\u6301\u8303\u56f4\u67e5\u8be2\uff0c\u53ea\u9002\u5408\u7b49\u503c\u67e5\u8be2\uff0c\u4e14\u54c8\u5e0c\u51b2\u7a81\u4e0b\u9000\u5316\u4e3a\u94fe\u8868<\/li>\n<li>InnoDB \u9875\u9762\u5927\u5c0f\u9ed8\u8ba4 16KB\uff0cB+ \u6811\u6bcf\u5c42\u80fd\u5b58\u7ea6 1170 \u4e2a\u6307\u9488\uff0c\u4e09\u5c42\u53ef\u5bfb\u5740\u7ea6 1170\u00b2 \u00d7 16 = 2000 \u4e07\u884c<\/li>\n<\/ul>\n<p><strong>Q20. \u805a\u7c07\u7d22\u5f15\u548c\u975e\u805a\u7c07\u7d22\u5f15\u7684\u533a\u522b\uff1f\u56de\u8868\u662f\u4ec0\u4e48\uff1f<\/strong><\/p>\n<p>\u7b54\u9898\u8981\u70b9\uff1a<\/p>\n<ul>\n<li>\u805a\u7c07\u7d22\u5f15\uff1a\u53f6\u8282\u70b9\u76f4\u63a5\u5b58\u884c\u6570\u636e\uff0cInnoDB \u7684\u4e3b\u952e\u7d22\u5f15\u5c31\u662f\u805a\u7c07\u7d22\u5f15\uff0c\u6570\u636e\u6309\u4e3b\u952e\u987a\u5e8f\u5b58\u50a8<\/li>\n<li>\u975e\u805a\u7c07\u7d22\u5f15\uff08\u4e8c\u7ea7\u7d22\u5f15\uff09\uff1a\u53f6\u8282\u70b9\u5b58\u7684\u662f\u4e3b\u952e\u503c\uff0c\u800c\u975e\u884c\u6570\u636e<\/li>\n<li>\u56de\u8868\uff1a\u901a\u8fc7\u4e8c\u7ea7\u7d22\u5f15\u627e\u5230\u4e3b\u952e\u540e\uff0c\u518d\u7528\u4e3b\u952e\u67e5\u805a\u7c07\u7d22\u5f15\u83b7\u53d6\u5b8c\u6574\u884c\u6570\u636e\uff0c\u4e24\u6b21 B+ \u6811\u67e5\u627e<\/li>\n<li>\u8986\u76d6\u7d22\u5f15\uff1a\u67e5\u8be2\u5217\u5168\u90e8\u5728\u7d22\u5f15\u4e2d\uff0c\u4e0d\u9700\u8981\u56de\u8868\u3002<code>EXPLAIN<\/code> \u4e2d <code>Extra: Using index<\/code> \u8868\u660e\u8986\u76d6\u7d22\u5f15\u547d\u4e2d<\/li>\n<\/ul>\n<p><strong>Q21. \u6700\u5de6\u5339\u914d\u539f\u5219\uff0c\u4ec0\u4e48\u60c5\u51b5\u4e0b\u8054\u5408\u7d22\u5f15\u4f1a\u5931\u6548\uff1f<\/strong><\/p>\n<p>\u7b54\u9898\u8981\u70b9\uff1a<\/p>\n<ul>\n<li>\u8054\u5408\u7d22\u5f15 <code>(a, b, c)<\/code> \u5b9e\u9645\u6309 a \u2192 b \u2192 c \u6392\u5e8f\u3002\u67e5\u8be2\u5fc5\u987b\u4ece\u6700\u5de6\u5217\u5f00\u59cb\uff0c\u4e14\u4e0d\u80fd\u8df3\u5217<\/li>\n<li>\u5931\u6548\u573a\u666f\uff1a\u8df3\u8fc7\u6700\u5de6\u5217\uff08<code>WHERE b=1<\/code>\uff0c\u4e0d\u7528 a\uff09\uff1b\u6700\u5de6\u5217\u4f7f\u7528\u8303\u56f4\u67e5\u8be2\u540e\uff0c\u540e\u7eed\u5217\u4e0d\u8d70\u7d22\u5f15\uff08<code>WHERE a &gt; 1 AND b = 2<\/code>\uff0cb \u4e0d\u8d70\u7d22\u5f15\uff09\uff1b\u5bf9\u7d22\u5f15\u5217\u4f7f\u7528\u51fd\u6570\uff08<code>WHERE YEAR(create_time) = 2024<\/code>\uff09\uff1b\u9690\u5f0f\u7c7b\u578b\u8f6c\u6362\uff08\u5b57\u7b26\u4e32\u5217\u7528\u6570\u5b57\u5339\u914d\uff09\uff1b<code>LIKE '%\u524d\u7f00'<\/code>\uff08\u901a\u914d\u7b26\u5728\u5f00\u5934\uff09<\/li>\n<\/ul>\n<p><strong>Q22. EXPLAIN \u6267\u884c\u8ba1\u5212\u600e\u4e48\u770b\uff1f\u91cd\u70b9\u5173\u6ce8\u54ea\u4e9b\u5b57\u6bb5\uff1f<\/strong><\/p>\n<p>\u7b54\u9898\u8981\u70b9\uff1a<\/p>\n<ul>\n<li><code>type<\/code>\uff1a\u8bbf\u95ee\u7c7b\u578b\uff0c\u6027\u80fd\u4ece\u597d\u5230\u5dee\uff1a<code>system &gt; const &gt; eq_ref &gt; ref &gt; range &gt; index &gt; ALL<\/code>\u3002ALL \u5c31\u662f\u5168\u8868\u626b\u63cf\uff0c\u9700\u8981\u4f18\u5316<\/li>\n<li><code>key<\/code>\uff1a\u5b9e\u9645\u4f7f\u7528\u7684\u7d22\u5f15\uff0cNULL \u8868\u793a\u672a\u547d\u4e2d\u7d22\u5f15<\/li>\n<li><code>rows<\/code>\uff1a\u4f30\u7b97\u626b\u63cf\u884c\u6570\uff0c\u8d8a\u5c0f\u8d8a\u597d<\/li>\n<li><code>Extra<\/code>\uff1a<code>Using index<\/code>\uff08\u8986\u76d6\u7d22\u5f15\uff09\u3001<code>Using where<\/code>\uff08\u9700\u8981\u518d\u8fc7\u6ee4\uff09\u3001<code>Using filesort<\/code>\uff08\u6587\u4ef6\u6392\u5e8f\uff0c\u53ef\u80fd\u9700\u8981\u52a0\u7d22\u5f15\uff09\u3001<code>Using temporary<\/code>\uff08\u7528\u4e86\u4e34\u65f6\u8868\uff0c\u9700\u8981\u4f18\u5316\uff09<\/li>\n<li><code>possible_keys<\/code> \u548c <code>key<\/code> \u4e0d\u4e00\u81f4\u65f6\uff0c\u8bf4\u660e\u4f18\u5316\u5668\u9009\u4e86\u53e6\u4e00\u4e2a\u7d22\u5f15\u6216\u653e\u5f03\u7d22\u5f15<\/li>\n<\/ul>\n<p><strong>Q23. MySQL \u7684\u4e8b\u52a1\u9694\u79bb\u7ea7\u522b\uff0c\u4ee5\u53ca InnoDB \u9ed8\u8ba4\u4f7f\u7528\u54ea\u79cd\uff1f<\/strong><\/p>\n<p>\u7b54\u9898\u8981\u70b9\uff1a<\/p>\n<ul>\n<li>4 \u79cd\u9694\u79bb\u7ea7\u522b\uff1aRead Uncommitted\uff08\u8bfb\u810f\u6570\u636e\uff09\u3001Read Committed\uff08\u4e0d\u53ef\u91cd\u590d\u8bfb\uff09\u3001Repeatable Read\uff08\u5e7b\u8bfb\u53ef\u80fd\uff09\u3001Serializable\uff08\u4e32\u884c\u5316\uff09<\/li>\n<li>InnoDB \u9ed8\u8ba4\uff1a<strong>Repeatable Read<\/strong>\uff0c\u4e14\u901a\u8fc7 Next-Key Lock\uff08\u884c\u9501 + \u95f4\u9699\u9501\uff09\u5728\u5927\u591a\u6570\u573a\u666f\u4e0b\u9632\u6b62\u5e7b\u8bfb\uff0c\u6bd4\u6807\u51c6 SQL \u5b9a\u4e49\u66f4\u4e25\u683c<\/li>\n<li>MVCC\uff08\u591a\u7248\u672c\u5e76\u53d1\u63a7\u5236\uff09\uff1a\u901a\u8fc7 undo log \u7ef4\u62a4\u7248\u672c\u94fe\uff0c\u8bfb\u64cd\u4f5c\u8bfb\u5feb\u7167\uff08\u5386\u53f2\u7248\u672c\uff09\uff0c\u5199\u64cd\u4f5c\u4e0d\u963b\u585e\u8bfb\uff0c\u5b9e\u73b0\u300c\u8bfb\u8bfb\u4e0d\u4e92\u65a5\u3001\u8bfb\u5199\u4e0d\u4e92\u65a5\u300d<\/li>\n<li>Read View\uff1a\u4e8b\u52a1\u5f00\u59cb\u65f6\u521b\u5efa\uff0c\u51b3\u5b9a\u54ea\u4e2a\u7248\u672c\u5bf9\u5f53\u524d\u4e8b\u52a1\u53ef\u89c1<\/li>\n<\/ul>\n<p><strong>Q24. InnoDB \u7684\u884c\u9501\u7c7b\u578b\u6709\u54ea\u4e9b\uff1f\u95f4\u9699\u9501\u7684\u4f5c\u7528\uff1f<\/strong><\/p>\n<p>\u7b54\u9898\u8981\u70b9\uff1a<\/p>\n<ul>\n<li>\u8bb0\u5f55\u9501\uff08Record Lock\uff09\uff1a\u9501\u5b9a\u5355\u884c<\/li>\n<li>\u95f4\u9699\u9501\uff08Gap Lock\uff09\uff1a\u9501\u5b9a\u7d22\u5f15\u8bb0\u5f55\u4e4b\u95f4\u7684\u95f4\u9699\uff0c\u9632\u6b62\u5176\u4ed6\u4e8b\u52a1\u63d2\u5165\uff0cRR \u7ea7\u522b\u4e0b\u7528\u4e8e\u9632\u5e7b\u8bfb<\/li>\n<li>Next-Key Lock = \u8bb0\u5f55\u9501 + \u95f4\u9699\u9501\uff0cInnoDB RR \u4e0b\u9ed8\u8ba4\u4f7f\u7528<\/li>\n<li>\u4e34\u952e\u9501\u964d\u7ea7\u573a\u666f\uff1a\u7b49\u503c\u67e5\u8be2\u547d\u4e2d\u552f\u4e00\u7d22\u5f15\u65f6\uff0c\u9000\u5316\u4e3a\u8bb0\u5f55\u9501\uff08\u65e0\u95f4\u9699\u9501\uff09\uff1b\u7b49\u503c\u67e5\u8be2\u4e0d\u5b58\u5728\u7684\u8bb0\u5f55\u65f6\uff0c\u9000\u5316\u4e3a\u95f4\u9699\u9501<\/li>\n<li>\u6b7b\u9501\u6392\u67e5\uff1a<code>SHOW ENGINE INNODB STATUS<\/code> \u67e5\u770b\u6700\u8fd1\u4e00\u6b21\u6b7b\u9501\u4fe1\u606f<\/li>\n<\/ul>\n<p><strong>Q25. redo log \u548c binlog \u7684\u533a\u522b\uff1f\u4e24\u9636\u6bb5\u63d0\u4ea4\u662f\u600e\u4e48\u56de\u4e8b\uff1f<\/strong><\/p>\n<p>\u8003\u5b98\u60f3\u542c\u7684\u89d2\u5ea6\uff1a\u8bf4\u51fa\u300c\u4e3a\u4ec0\u4e48\u9700\u8981\u4e24\u9636\u6bb5\u63d0\u4ea4\u300d\uff0c\u800c\u4e0d\u53ea\u662f\u63cf\u8ff0\u683c\u5f0f\u5dee\u5f02\u3002<\/p>\n<p>\u7b54\u9898\u8981\u70b9\uff1a<\/p>\n<ul>\n<li>redo log \u662f InnoDB \u5c42\u7684\u7269\u7406\u65e5\u5fd7\uff08\u9875\u7684\u4fee\u6539\uff09\uff0c\u7528\u4e8e\u5d29\u6e83\u6062\u590d\uff0c\u5faa\u73af\u5199\u8986\u76d6<\/li>\n<li>binlog \u662f MySQL Server \u5c42\u7684\u903b\u8f91\u65e5\u5fd7\uff08SQL \u6216\u884c\u53d8\u66f4\uff09\uff0c\u7528\u4e8e\u4e3b\u4ece\u590d\u5236\u3001\u65f6\u95f4\u70b9\u6062\u590d\uff0c\u8ffd\u52a0\u5199<\/li>\n<li>\u4e24\u9636\u6bb5\u63d0\u4ea4\uff1a\u5148\u5199 redo log\uff08prepare \u72b6\u6001\uff09\u2192 \u5199 binlog \u2192 redo log \u63d0\u4ea4\u3002\u76ee\u7684\u662f\u4fdd\u8bc1 redo log \u548c binlog \u7684\u4e00\u81f4\u6027\u2014\u2014\u5982\u679c\u53ea\u5199\u4e00\u4e2a\u7136\u540e\u5d29\u6e83\uff0c\u4f1a\u51fa\u73b0\u300cbinlog \u6709\u4f46 redo log \u6ca1\u6709\u300d\u6216\u53cd\u5411\u4e0d\u4e00\u81f4\u7684\u60c5\u51b5\uff0c\u5bfc\u81f4\u4e3b\u4ece\u6570\u636e\u4e0d\u540c\u6b65<\/li>\n<\/ul>\n<p><strong>Q26. \u4ec0\u4e48\u662f\u6162\u67e5\u8be2\uff1f\u5982\u4f55\u5b9a\u4f4d\u548c\u4f18\u5316\uff1f<\/strong><\/p>\n<p>\u7b54\u9898\u8981\u70b9\uff1a<\/p>\n<ul>\n<li>\u6162\u67e5\u8be2\u65e5\u5fd7\uff1a<code>slow_query_log=ON<\/code>\uff0c<code>long_query_time=1<\/code>\uff08\u9ed8\u8ba4 1 \u79d2\uff09\uff0c\u8bb0\u5f55\u8d85\u65f6\u67e5\u8be2<\/li>\n<li>\u5206\u6790\u5de5\u5177\uff1a<code>pt-query-digest<\/code> \u6309\u6267\u884c\u9891\u7387 \u00d7 \u8017\u65f6\u6392\u5e8f\uff0c\u627e\u51fa\u6700\u503c\u5f97\u4f18\u5316\u7684 SQL<\/li>\n<li>\u4f18\u5316\u601d\u8def\uff1a\u52a0\u7d22\u5f15\uff08\u5148 EXPLAIN \u786e\u8ba4\uff09\u2192 \u6539\u5199 SQL\uff08\u907f\u514d <code>SELECT *<\/code>\u3001\u907f\u514d\u51fd\u6570\u8ba1\u7b97\u7d22\u5f15\u5217\uff09\u2192 \u5206\u9875\u4f18\u5316\uff08\u5927 offset \u7528 <code>WHERE id &gt; last_id<\/code>\uff09\u2192 \u5206\u8868\uff08\u6570\u636e\u91cf\u8d85\u8fc7 5000 \u4e07\u8003\u8651\uff09<\/li>\n<\/ul>\n<p><strong>Q27. MVCC \u7684 Read View \u548c\u7248\u672c\u94fe\u662f\u600e\u4e48\u5de5\u4f5c\u7684\uff1f<\/strong><\/p>\n<p>\u7b54\u9898\u8981\u70b9\uff1a<\/p>\n<ul>\n<li>\u6bcf\u884c\u6570\u636e\u6709\u4e24\u4e2a\u9690\u85cf\u5b57\u6bb5\uff1a<code>trx_id<\/code>\uff08\u6700\u540e\u4fee\u6539\u8be5\u884c\u7684\u4e8b\u52a1 ID\uff09\u548c <code>roll_pointer<\/code>\uff08\u6307\u5411 undo log \u7684\u7248\u672c\u94fe\uff09<\/li>\n<li>Read View \u5305\u542b\uff1a<code>m_ids<\/code>\uff08\u5f53\u524d\u6d3b\u8dc3\u4e8b\u52a1\u5217\u8868\uff09\u3001<code>min_trx_id<\/code>\u3001<code>max_trx_id<\/code>\u3001<code>creator_trx_id<\/code><\/li>\n<li>\u53ef\u89c1\u6027\u5224\u65ad\uff1atrx_id &lt; min_trx_id \u2192 \u53ef\u89c1\uff08\u5df2\u63d0\u4ea4\uff09\uff1btrx_id &gt; max_trx_id \u2192 \u4e0d\u53ef\u89c1\uff08\u540e\u5f00\u59cb\uff09\uff1b\u5728 m_ids \u91cc \u2192 \u4e0d\u53ef\u89c1\uff08\u672a\u63d0\u4ea4\uff09\uff1b\u4e0d\u5728 m_ids \u91cc\u4e14\u5728\u8303\u56f4\u5185 \u2192 \u53ef\u89c1\uff08\u5df2\u63d0\u4ea4\uff09<\/li>\n<li>RC \u6bcf\u6b21\u8bfb\u90fd\u521b\u5efa\u65b0 Read View\uff08\u6240\u4ee5\u53ef\u4ee5\u8bfb\u5230\u5176\u4ed6\u4e8b\u52a1\u65b0\u63d0\u4ea4\u7684\u6570\u636e\uff09\uff0cRR \u53ea\u5728\u4e8b\u52a1\u5f00\u59cb\u65f6\u521b\u5efa\u4e00\u6b21<\/li>\n<\/ul>\n<h2>Redis\uff1a\u7f13\u5b58\u7b56\u7565 + \u6570\u636e\u7ed3\u6784 + \u6301\u4e45\u5316\u4e09\u4ef6\u5957<\/h2>\n<p>\u5b57\u8282 Redis \u6a21\u5757\u7684\u7279\u70b9\u662f\u4e0d\u53ea\u8003\u300c\u8bf4\u4e00\u4e0b\u7f13\u5b58\u7a7f\u900f\u300d\uff0c\u4f1a\u8ffd\u95ee\u300c\u4f60\u4eec\u7528\u7684\u54ea\u79cd\u5e03\u9686\u8fc7\u6ee4\u5668\u5b9e\u73b0\u3001\u8bef\u5224\u7387\u662f\u591a\u5c11\u300d\u8fd9\u7c7b\u9700\u8981\u5b9e\u9645\u64cd\u4f5c\u7ecf\u9a8c\u7684\u95ee\u9898\u3002<\/p>\n<p><strong>Q28. Redis \u4e3a\u4ec0\u4e48\u5feb\uff1f\u5355\u7ebf\u7a0b\u4e0d\u662f\u5e94\u8be5\u6162\u5417\uff1f<\/strong><\/p>\n<p>\u8003\u5b98\u60f3\u542c\u7684\u89d2\u5ea6\uff1a\u8fd9\u662f\u5b57\u8282\u9ad8\u9891\u95ee\u6cd5\uff0c\u6709\u53cd\u76f4\u89c9\u7684\u5473\u9053\uff0c\u8981\u8bf4\u51fa\u300c\u5355\u7ebf\u7a0b\u907f\u514d\u4e86\u4ec0\u4e48\u300d\u3002<\/p>\n<p>\u7b54\u9898\u8981\u70b9\uff1a<\/p>\n<ul>\n<li>\u57fa\u4e8e\u5185\u5b58\u64cd\u4f5c\uff08\u65e0\u78c1\u76d8 I\/O\uff09\uff1a\u5185\u5b58\u8bbf\u95ee\u901f\u5ea6\u662f\u78c1\u76d8\u7684 10 \u4e07\u500d<\/li>\n<li>\u5355\u7ebf\u7a0b\u6a21\u578b\uff1a\u907f\u514d\u4e86\u591a\u7ebf\u7a0b\u7684\u4e0a\u4e0b\u6587\u5207\u6362\u5f00\u9500\u548c\u9501\u7ade\u4e89\uff0cCPU \u65f6\u95f4\u90fd\u82b1\u5728\u5904\u7406\u547d\u4ee4\u4e0a<\/li>\n<li>IO \u591a\u8def\u590d\u7528\uff1a\u7528 epoll\uff08Linux\uff09\u76d1\u542c\u591a\u4e2a\u8fde\u63a5\u7684 I\/O \u4e8b\u4ef6\uff0c\u5355\u7ebf\u7a0b\u5904\u7406\u591a\u4e2a\u8fde\u63a5\uff0c\u4e0d\u963b\u585e<\/li>\n<li>\u9ad8\u6548\u6570\u636e\u7ed3\u6784\uff1aziplist\/listpack \u538b\u7f29\u5b58\u50a8\u5c0f\u5bf9\u8c61\uff0c\u8df3\u8868\u505a\u6709\u5e8f\u96c6\u5408\uff0c\u76f8\u6bd4 B \u6811\u51cf\u5c11\u5185\u5b58\u5206\u914d<\/li>\n<li>\u6ce8\u610f\uff1a6.0 \u4e4b\u540e\u5f15\u5165\u4e86 IO \u591a\u7ebf\u7a0b\uff08\u8bfb\u5199\u7f51\u7edc\u6570\u636e\u7528\u591a\u7ebf\u7a0b\uff0c\u547d\u4ee4\u6267\u884c\u4ecd\u7136\u5355\u7ebf\u7a0b\uff09<\/li>\n<\/ul>\n<p><strong>Q29. \u7f13\u5b58\u7a7f\u900f\u3001\u7f13\u5b58\u51fb\u7a7f\u3001\u7f13\u5b58\u96ea\u5d29\uff0c\u5206\u522b\u600e\u4e48\u89e3\u51b3\uff1f<\/strong><\/p>\n<p>\u7b54\u9898\u8981\u70b9\uff1a<\/p>\n<p><strong>\u7f13\u5b58\u7a7f\u900f<\/strong>\uff08\u67e5\u8be2\u4e0d\u5b58\u5728\u7684\u6570\u636e\uff0c\u6bcf\u6b21\u90fd\u6253\u5230 DB\uff09\uff1a<\/p>\n<ul>\n<li>\u5e03\u9686\u8fc7\u6ee4\u5668\uff1a\u8bf7\u6c42\u524d\u5148\u95ee\u8fc7\u6ee4\u5668\uff0c\u4e0d\u5b58\u5728\u7684\u76f4\u63a5\u62e6\u622a<\/li>\n<li>\u7f13\u5b58\u7a7a\u503c\uff1aDB \u6ca1\u6709\u65f6\u4e5f\u7f13\u5b58\u4e00\u4e2a null\uff08\u77ed TTL\uff0c\u5982 60 \u79d2\uff09\uff0c\u9632\u6b62\u6076\u610f\u91cd\u590d\u8bf7\u6c42<\/li>\n<\/ul>\n<p><strong>\u7f13\u5b58\u51fb\u7a7f<\/strong>\uff08\u70ed key \u8fc7\u671f\uff0c\u5927\u91cf\u8bf7\u6c42\u540c\u65f6\u7a7f\u900f\u5230 DB\uff09\uff1a<\/p>\n<ul>\n<li>\u4e92\u65a5\u9501\uff1a\u7b2c\u4e00\u4e2a\u8bf7\u6c42\u52a0\u9501\u53bb DB \u67e5\uff0c\u5176\u4f59\u7b49\u5f85\uff0c\u9501\u91ca\u653e\u540e\u4ece\u7f13\u5b58\u8bfb<\/li>\n<li>\u70ed key \u4e0d\u8fc7\u671f\uff08\u903b\u8f91\u8fc7\u671f\uff09\uff1akey \u6c38\u4e0d\u8fc7\u671f\uff0cvalue \u91cc\u5b58\u8fc7\u671f\u65f6\u95f4\uff0c\u540e\u53f0\u5f02\u6b65\u5237\u65b0<\/li>\n<\/ul>\n<p><strong>\u7f13\u5b58\u96ea\u5d29<\/strong>\uff08\u5927\u91cf key \u540c\u65f6\u8fc7\u671f\u6216 Redis \u5b95\u673a\uff0c\u8bf7\u6c42\u5168\u6253\u5230 DB\uff09\uff1a<\/p>\n<ul>\n<li>TTL \u52a0\u968f\u673a\u503c\uff0c\u907f\u514d\u540c\u65f6\u8fc7\u671f<\/li>\n<li>Redis \u96c6\u7fa4\uff0c\u907f\u514d\u5355\u70b9\u6545\u969c<\/li>\n<li>\u7194\u65ad\u964d\u7ea7\uff0cDB \u538b\u529b\u8fc7\u5927\u65f6\u76f4\u63a5\u8fd4\u56de\u964d\u7ea7\u7ed3\u679c<\/li>\n<\/ul>\n<p><strong>Q30. Redis \u6301\u4e45\u5316\uff1aRDB \u548c AOF \u600e\u4e48\u9009\uff1f<\/strong><\/p>\n<p>\u8003\u5b98\u60f3\u542c\u7684\u89d2\u5ea6\uff1a\u8bf4\u51fa\u5404\u81ea\u7684\u6570\u636e\u4e22\u5931\u91cf\u548c\u6027\u80fd\u4ee3\u4ef7\uff0c\u800c\u4e0d\u662f\u53ea\u5217\u683c\u5f0f\u5dee\u5f02\u3002<\/p>\n<p>\u7b54\u9898\u8981\u70b9\uff1a<\/p>\n<ul>\n<li>RDB\uff1aBGSAVE \u5b50\u8fdb\u7a0b fork + \u5199\u65f6\u590d\u5236\uff0c\u4e0d\u5f71\u54cd\u4e3b\u7ebf\u7a0b\u3002\u6062\u590d\u5feb\uff08\u76f4\u63a5\u52a0\u8f7d\u5feb\u7167\uff09\uff0c\u4f46\u6700\u591a\u4e22\u5931\u4e0a\u6b21 RDB \u5230\u5d29\u6e83\u65f6\u95f4\u6bb5\u7684\u6570\u636e\uff08\u751f\u4ea7\u91cc\u901a\u5e38 5-15 \u5206\u949f\uff09<\/li>\n<li>AOF\uff1a\u6bcf\u6761\u5199\u547d\u4ee4\u8ffd\u52a0\u5230\u6587\u4ef6\uff0c<code>appendfsync always<\/code>\uff08\u6bcf\u6b21\u5237\u76d8\uff0c\u6700\u5b89\u5168\uff0c\u6027\u80fd\u6700\u5dee\uff09\u3001<code>everysec<\/code>\uff08\u6bcf\u79d2\u5237\uff0c\u6700\u591a\u4e22 1 \u79d2\uff09\u3001<code>no<\/code>\uff08OS \u51b3\u5b9a\uff0c\u6027\u80fd\u6700\u597d\u4f46\u4e0d\u53ef\u63a7\uff09<\/li>\n<li>AOF \u91cd\u5199\uff08BGREWRITEAOF\uff09\uff1a\u538b\u7f29\u65e5\u5fd7\uff0c\u5408\u5e76\u5197\u4f59\u547d\u4ee4\uff0c4.0+ \u652f\u6301\u6df7\u5408\u6301\u4e45\u5316\uff08\u5148\u5199 RDB \u5feb\u7167\uff0c\u518d\u8ffd\u52a0 AOF \u589e\u91cf\uff09\uff0c\u517c\u987e\u6062\u590d\u901f\u5ea6\u548c\u6570\u636e\u5b89\u5168<\/li>\n<li><strong>\u751f\u4ea7\u5e38\u89c1\u9009\u62e9<\/strong>\uff1aAOF <code>everysec<\/code> + \u6bcf\u5929 RDB \u5907\u4efd\uff0c\u5e73\u8861\u6570\u636e\u5b89\u5168\u548c\u6062\u590d\u901f\u5ea6<\/li>\n<\/ul>\n<p><strong>Q31. Redis \u7684\u6570\u636e\u7c7b\u578b\u53ca\u5176\u5e95\u5c42\u5b9e\u73b0\uff1f<\/strong><\/p>\n<p>\u7b54\u9898\u8981\u70b9\uff1a<\/p>\n<ul>\n<li>String\uff1aSDS\uff08Simple Dynamic String\uff09\uff0cO(1) \u83b7\u53d6\u957f\u5ea6\uff0c\u9884\u5206\u914d\u7a7a\u95f4\uff0c\u4e8c\u8fdb\u5236\u5b89\u5168<\/li>\n<li>List\uff1aziplist\uff08\u5c0f\u5217\u8868\uff0c&lt;128 \u5143\u7d20\u4e14\u5143\u7d20 &lt;64 \u5b57\u8282\uff09\u6216 quicklist\uff08\u5927\u5217\u8868\uff0c\u591a\u4e2a ziplist \u8282\u70b9\u7ec4\u6210\u7684\u53cc\u5411\u94fe\u8868\uff09\u30027.0 \u4e4b\u540e ziplist \u88ab listpack \u66ff\u4ee3<\/li>\n<li>Hash\uff1aziplist\uff08\u5c0f\u54c8\u5e0c\uff09\u6216 hashtable\uff08\u5927\u54c8\u5e0c\uff09<\/li>\n<li>Set\uff1aintset\uff08\u5168\u6574\u6570\u7684\u5c0f\u96c6\u5408\uff09\u6216 hashtable<\/li>\n<li>ZSet\uff1aziplist\uff08\u5c0f\u6709\u5e8f\u96c6\u5408\uff09\u6216 skiplist + hashtable\uff08\u5927\u6709\u5e8f\u96c6\u5408\uff09<\/li>\n<\/ul>\n<p><strong>Q32. Redis \u7684\u8fc7\u671f\u5220\u9664\u7b56\u7565\u548c\u5185\u5b58\u6dd8\u6c70\u7b56\u7565\uff1f<\/strong><\/p>\n<p>\u7b54\u9898\u8981\u70b9\uff1a<\/p>\n<ul>\n<li>\u8fc7\u671f\u5220\u9664\uff1a<strong>\u60f0\u6027\u5220\u9664<\/strong>\uff08\u8bbf\u95ee\u65f6\u68c0\u67e5\u662f\u5426\u8fc7\u671f\uff0c\u8fc7\u671f\u5219\u5220\uff09+ <strong>\u5b9a\u671f\u5220\u9664<\/strong>\uff08\u5468\u671f\u6027\u968f\u673a\u68c0\u67e5\u90e8\u5206 key\uff0c\u5220\u8fc7\u671f\u7684\uff09\uff0c\u4e24\u8005\u7ed3\u5408<\/li>\n<li>\u5185\u5b58\u6dd8\u6c70\uff08maxmemory \u89e6\u53d1\uff09\uff1a8 \u79cd\u7b56\u7565\uff0c\u5e38\u7528\u7684\u6709 <code>allkeys-lru<\/code>\uff08\u5168\u90e8 key \u4e2d LRU \u6dd8\u6c70\uff0c\u7f13\u5b58\u573a\u666f\u63a8\u8350\uff09\u3001<code>volatile-lru<\/code>\uff08\u53ea\u6dd8\u6c70\u8bbe\u4e86 TTL \u7684 key\uff09\u3001<code>allkeys-random<\/code>\u3001<code>noeviction<\/code>\uff08\u62d2\u7edd\u5199\uff09<\/li>\n<li>\u751f\u4ea7\u5efa\u8bae\uff1a\u7f13\u5b58\u573a\u666f\u7528 <code>allkeys-lru<\/code>\uff0c\u907f\u514d\u6ca1\u8bbe TTL \u7684 key \u6c38\u4e0d\u6dd8\u6c70\u6491\u6ee1\u5185\u5b58<\/li>\n<\/ul>\n<p><strong>Q33. Redis \u5206\u5e03\u5f0f\u9501\u7684\u5b9e\u73b0\uff0c\u4ee5\u53ca Redlock \u7684\u95ee\u9898\uff1f<\/strong><\/p>\n<p>\u7b54\u9898\u8981\u70b9\uff1a<\/p>\n<ul>\n<li>\u57fa\u7840\u5b9e\u73b0\uff1a<code>SET key value NX PX 30000<\/code>\uff08\u539f\u5b50\u64cd\u4f5c\uff0cNX \u4e0d\u5b58\u5728\u624d\u8bbe\uff0cPX \u8bbe\u6beb\u79d2\u8fc7\u671f\uff09<\/li>\n<li>\u91ca\u653e\u9501\u5fc5\u987b\u9a8c\u8bc1 value\uff08\u968f\u673a\u503c\uff09\uff0c\u9632\u6b62\u8bef\u91ca\u653e\u5176\u4ed6\u7ebf\u7a0b\u7684\u9501\uff1a\u7528 Lua \u811a\u672c\u4fdd\u8bc1\u300c\u5224\u65ad + \u5220\u9664\u300d\u539f\u5b50\u6027<\/li>\n<li>\u9501\u7eed\u671f\uff1aRedisson \u7684 WatchDog \u673a\u5236\uff0c\u6301\u9501\u7ebf\u7a0b\u8fd8\u5728\u5c31\u81ea\u52a8\u7eed\u671f\uff08\u6bcf 10 \u79d2\u68c0\u67e5\uff0cTTL\/3 \u65f6\u7eed\u671f\uff09<\/li>\n<li>Redlock\uff1aAntirez \u63d0\u51fa\u7684\u591a\u8282\u70b9\uff085 \u4e2a\u72ec\u7acb Redis\uff09\u65b9\u6848\uff0c\u5728\u5927\u591a\u6570\u8282\u70b9\u52a0\u9501\u6210\u529f\u624d\u7b97\u52a0\u9501\u6210\u529f\u3002\u4f46 Martin Kleppmann \u6307\u51fa GC Stop-the-World \u6216\u7f51\u7edc\u5206\u533a\u65f6\u4ecd\u6709\u5b89\u5168\u6f0f\u6d1e\uff0c\u4e89\u8bae\u6301\u7eed\u81f3\u4eca<\/li>\n<li>\u751f\u4ea7\u5efa\u8bae\uff1a\u5355 Redis + WatchDog \u5df2\u7ecf\u591f\u7528\uff0cRedlock \u5f15\u5165\u7684\u590d\u6742\u5ea6\u901a\u5e38\u4e0d\u503c\u5f97<\/li>\n<\/ul>\n<h2>\u7f51\u7edc\u4e0e\u64cd\u4f5c\u7cfb\u7edf\uff1a\u8003\u6df1\u5ea6\u4e0d\u8003\u5e7f\u5ea6<\/h2>\n<p>\u5b57\u8282\u7f51\u7edc\u6a21\u5757\u4e0d\u8003\u300cOSI \u4e03\u5c42\u6a21\u578b\u662f\u4ec0\u4e48\u300d\uff0c\u8003\u7684\u662f\u300cTIME_WAIT \u4e3a\u4ec0\u4e48\u7b49 2MSL\u300d\u300cepoll \u548c select \u7684\u6027\u80fd\u5dee\u8ddd\u4ece\u54ea\u6765\u300d\u8fd9\u7c7b\u9700\u8981\u7406\u89e3\u5e95\u5c42\u7684\u95ee\u9898\u3002<\/p>\n<p><strong>Q34. TCP \u4e09\u6b21\u63e1\u624b\u7684\u8fc7\u7a0b\uff0c\u4e3a\u4ec0\u4e48\u4e0d\u80fd\u662f\u4e24\u6b21\uff1f<\/strong><\/p>\n<p>\u8003\u5b98\u60f3\u542c\u7684\u89d2\u5ea6\uff1a\u8bf4\u51fa\u300c\u4e24\u6b21\u63e1\u624b\u7684\u5177\u4f53\u95ee\u9898\u662f\u4ec0\u4e48\u300d\uff0c\u800c\u4e0d\u53ea\u662f\u590d\u8ff0\u6d41\u7a0b\u3002<\/p>\n<p>\u7b54\u9898\u8981\u70b9\uff1a<\/p>\n<ul>\n<li>\u6d41\u7a0b\uff1aSYN \u2192 SYN-ACK \u2192 ACK\uff0c\u53cc\u65b9\u5206\u522b\u786e\u8ba4\u5bf9\u65b9\u7684\u53d1\u9001\u548c\u63a5\u6536\u80fd\u529b<\/li>\n<li>\u4e3a\u4ec0\u4e48\u4e24\u6b21\u4e0d\u591f\uff1a\u670d\u52a1\u7aef\u53d1 SYN-ACK \u540e\u4e0d\u77e5\u9053\u5ba2\u6237\u7aef\u80fd\u5426\u6536\u5230\uff0c\u82e5\u5ba2\u6237\u7aef\u4e4b\u524d\u7684 SYN \u5728\u7f51\u7edc\u4e2d\u5ef6\u8fdf\u5230\u8fbe\uff0c\u670d\u52a1\u7aef\u4f1a\u5f00\u542f\u4e00\u4e2a\u65e0\u6548\u8fde\u63a5\u7b49\u5f85\uff0c\u4e24\u6b21\u63e1\u624b\u4f1a\u6d6a\u8d39\u670d\u52a1\u7aef\u8d44\u6e90<\/li>\n<li>\u4e09\u6b21\u63e1\u624b\u7684\u672c\u8d28\uff1a\u8ba9\u53cc\u65b9\u90fd\u786e\u8ba4\u300c\u6211\u7684 seq \u5bf9\u65b9\u6536\u5230\u4e86\uff0c\u5bf9\u65b9\u7684 seq \u6211\u4e5f\u786e\u8ba4\u4e86\u300d\uff0c\u4fdd\u8bc1 ISN \u540c\u6b65<\/li>\n<\/ul>\n<p><strong>Q35. TIME_WAIT \u72b6\u6001\u4e3a\u4ec0\u4e48\u7b49 2MSL\uff1f\u5927\u91cf TIME_WAIT \u600e\u4e48\u5904\u7406\uff1f<\/strong><\/p>\n<p>\u7b54\u9898\u8981\u70b9\uff1a<\/p>\n<ul>\n<li>2MSL\uff08\u6700\u5927\u62a5\u6587\u6bb5\u751f\u5b58\u65f6\u95f4 \u00d7 2\uff0c\u901a\u5e38 60-120 \u79d2\uff09\u7684\u76ee\u7684\uff1a\u786e\u4fdd\u6700\u540e\u4e00\u4e2a ACK \u80fd\u5230\u8fbe\u5bf9\u7aef\uff1b\u7b49\u5f85\u7f51\u7edc\u4e2d\u6b8b\u4f59\u5206\u7ec4\u6d88\u5931\uff08\u5982\u679c\u7acb\u523b\u91cd\u7528\u7aef\u53e3\uff0c\u65e7\u8fde\u63a5\u7684\u5ef6\u8fdf\u6570\u636e\u53ef\u80fd\u5e72\u6270\u65b0\u8fde\u63a5\uff09<\/li>\n<li>\u5927\u91cf TIME_WAIT \u7684\u5e38\u89c1\u573a\u666f\uff1aHTTP \u77ed\u8fde\u63a5\uff0c\u670d\u52a1\u7aef\u4e3b\u52a8\u5173\u95ed\uff08\u56db\u6b21\u6325\u624b\u7684\u4e3b\u52a8\u65b9\u8fdb\u5165 TIME_WAIT\uff09<\/li>\n<li>\u89e3\u51b3\u65b9\u6848\uff1a\u542f\u7528 <code>SO_REUSEADDR<\/code> + <code>tcp_tw_reuse<\/code>\uff08\u5141\u8bb8 TIME_WAIT \u7aef\u53e3\u7528\u4e8e\u65b0\u8fde\u63a5\uff0c\u9700\u914d\u5408\u65f6\u95f4\u6233 PAWS\uff09\uff1b\u542f\u7528 HTTP Keep-Alive \u51cf\u5c11\u8fde\u63a5\u521b\u5efa\/\u9500\u6bc1\u6b21\u6570<\/li>\n<\/ul>\n<p><strong>Q36. epoll \u76f8\u6bd4 select\/poll \u7684\u4f18\u52bf\u5728\u54ea\u91cc\uff1f<\/strong><\/p>\n<p>\u8003\u5b98\u60f3\u542c\u7684\u89d2\u5ea6\uff1a\u4ece\u300c\u6bcf\u6b21\u8c03\u7528\u7684\u5f00\u9500\u300d\u548c\u300c\u4e8b\u4ef6\u901a\u77e5\u673a\u5236\u300d\u4e24\u4e2a\u7ef4\u5ea6\u8bf4\uff0c\u800c\u4e0d\u53ea\u8bf4\u300cepoll \u6ca1\u6709\u6570\u91cf\u9650\u5236\u300d\u3002<\/p>\n<p>\u7b54\u9898\u8981\u70b9\uff1a<\/p>\n<ul>\n<li>select\/poll \u6bcf\u6b21\u8c03\u7528\u90fd\u628a fd \u96c6\u5408\u4ece\u7528\u6237\u7a7a\u95f4\u62f7\u8d1d\u5230\u5185\u6838\uff0c\u5185\u6838\u904d\u5386\u6240\u6709 fd \u68c0\u67e5\u72b6\u6001\uff0cO(n) \u5f00\u9500<\/li>\n<li>epoll \u6ce8\u518c fd \u53ea\u62f7\u8d1d\u4e00\u6b21\uff08<code>epoll_ctl<\/code>\uff09\uff0c\u5185\u6838\u7528\u7ea2\u9ed1\u6811\u7ef4\u62a4\u76d1\u542c fd\uff0c\u4e8b\u4ef6\u53d1\u751f\u65f6\u901a\u8fc7\u56de\u8c03\u52a0\u5165\u5c31\u7eea\u94fe\u8868\uff08<code>epoll_wait<\/code> \u53ea\u8fd4\u56de\u5c31\u7eea\u7684 fd\uff09\uff0cO(1) \u590d\u6742\u5ea6<\/li>\n<li>ET\uff08\u8fb9\u7f18\u89e6\u53d1\uff09vs LT\uff08\u6c34\u5e73\u89e6\u53d1\uff09\uff1aET \u53ea\u5728\u72b6\u6001\u53d8\u5316\u65f6\u901a\u77e5\u4e00\u6b21\uff0c\u8981\u6c42\u5355\u6b21 read \u8bfb\u5b8c\uff0c\u5426\u5219\u4e22\u4e8b\u4ef6\uff1bLT \u53ea\u8981\u7f13\u51b2\u533a\u6709\u6570\u636e\u5c31\u6301\u7eed\u901a\u77e5\uff0c\u7f16\u7a0b\u66f4\u7b80\u5355<\/li>\n<li>Redis \u7528 epoll\uff08Linux\uff09\uff0cMac \u4e0a\u7528 kqueue<\/li>\n<\/ul>\n<p><strong>Q37. TCP \u5982\u4f55\u4fdd\u8bc1\u53ef\u9760\u4f20\u8f93\uff1f<\/strong><\/p>\n<p>\u7b54\u9898\u8981\u70b9\uff1a<\/p>\n<ul>\n<li>\u5e8f\u53f7 + \u786e\u8ba4\u5e94\u7b54\uff08ACK\uff09\uff1a\u4e22\u5305\u91cd\u4f20<\/li>\n<li>\u8d85\u65f6\u91cd\u4f20\uff1aRTO \u81ea\u9002\u5e94\u8ba1\u7b97\uff08\u57fa\u4e8e RTT \u91c7\u6837\uff09<\/li>\n<li>\u6ed1\u52a8\u7a97\u53e3\uff1a\u6d41\u91cf\u63a7\u5236\uff0c\u63a5\u6536\u65b9\u901a\u544a\u7a97\u53e3\u5927\u5c0f\u9650\u5236\u53d1\u9001\u901f\u7387<\/li>\n<li>\u62e5\u585e\u63a7\u5236\uff1a\u6162\u542f\u52a8 \u2192 \u62e5\u585e\u907f\u514d \u2192 \u5feb\u901f\u91cd\u4f20 \u2192 \u5feb\u901f\u6062\u590d\uff08CUBIC \u7b49\u7b97\u6cd5\uff09<\/li>\n<li>\u6821\u9a8c\u548c\uff1a\u9a8c\u8bc1\u6570\u636e\u5b8c\u6574\u6027<\/li>\n<\/ul>\n<p><strong>Q38. HTTP\/1.1\u3001HTTP\/2\u3001HTTP\/3 \u7684\u4e3b\u8981\u5dee\u5f02\uff1f<\/strong><\/p>\n<p>\u7b54\u9898\u8981\u70b9\uff1a<\/p>\n<ul>\n<li>HTTP\/1.1\uff1akeep-alive \u590d\u7528\u8fde\u63a5\uff0c\u4f46 HOL \u963b\u585e\uff08\u540c\u4e00\u8fde\u63a5\u540e\u7eed\u8bf7\u6c42\u5fc5\u987b\u7b49\u524d\u4e00\u4e2a\u54cd\u5e94\uff09<\/li>\n<li>HTTP\/2\uff1a\u4e8c\u8fdb\u5236\u5206\u5e27\uff0c\u591a\u8def\u590d\u7528\uff08\u4e00\u4e2a TCP \u8fde\u63a5\u5e76\u884c\u591a\u4e2a\u8bf7\u6c42\/\u54cd\u5e94\u6d41\uff09\uff0cHeader \u538b\u7f29\uff08HPACK\uff09\uff0c\u670d\u52a1\u5668\u63a8\u9001\u3002\u4f46 TCP \u5c42 HOL \u963b\u585e\u4ecd\u5b58\u5728\uff08\u4e22\u5305\u65f6\u6574\u4e2a\u8fde\u63a5\u963b\u585e\uff09<\/li>\n<li>HTTP\/3\uff1a\u57fa\u4e8e QUIC\uff08UDP\uff09\uff0c\u6bcf\u4e2a Stream \u72ec\u7acb\uff0c\u4e22\u5305\u53ea\u5f71\u54cd\u8be5 Stream\uff1b0-RTT \u8fde\u63a5\u5efa\u7acb\uff1b\u5185\u7f6e TLS 1.3<\/li>\n<li>\u751f\u4ea7\u91cc HTTP\/3 \u9700\u8981 CDN \u652f\u6301\uff0c\u540e\u7aef\u670d\u52a1\u95f4\u901a\u4fe1\u66f4\u591a\u7528 gRPC\uff08HTTP\/2\uff09<\/li>\n<\/ul>\n<p><strong>Q39. \u8fdb\u7a0b\u548c\u7ebf\u7a0b\u7684\u533a\u522b\uff0c\u4ec0\u4e48\u662f\u534f\u7a0b\uff1f<\/strong><\/p>\n<p>\u7b54\u9898\u8981\u70b9\uff1a<\/p>\n<ul>\n<li>\u8fdb\u7a0b\u662f\u8d44\u6e90\u5206\u914d\u5355\u4f4d\uff08\u5730\u5740\u7a7a\u95f4\u3001\u6587\u4ef6\u63cf\u8ff0\u7b26\uff09\uff0c\u7ebf\u7a0b\u662f\u8c03\u5ea6\u5355\u4f4d\uff0c\u5171\u4eab\u8fdb\u7a0b\u8d44\u6e90<\/li>\n<li>\u4e0a\u4e0b\u6587\u5207\u6362\u4ee3\u4ef7\uff1a\u8fdb\u7a0b\u5207\u6362\u8981\u5207\u6362\u5730\u5740\u7a7a\u95f4\uff08TLB \u5237\u65b0\uff09\uff0c\u4ee3\u4ef7\u5927\uff1b\u7ebf\u7a0b\u5171\u4eab\u5730\u5740\u7a7a\u95f4\uff0c\u4ee3\u4ef7\u5c0f<\/li>\n<li>\u534f\u7a0b\uff08Coroutine\uff09\uff1a\u7528\u6237\u6001\u7684\u8c03\u5ea6\uff0c\u534f\u7a0b\u5207\u6362\u4e0d\u7ecf\u8fc7\u5185\u6838\uff0c\u4ee3\u4ef7\u6781\u5c0f\uff08\u4fdd\u5b58\/\u6062\u590d\u5bc4\u5b58\u5668 + \u6808\u5e27\uff09\u3002Java 21 \u7684\u865a\u62df\u7ebf\u7a0b\uff08Virtual Thread\uff09\u672c\u8d28\u662f\u534f\u7a0b\uff0c100 \u4e07\u4e2a\u5e76\u53d1\u5199\u6cd5\u548c\u666e\u901a\u7ebf\u7a0b\u4e00\u6837<\/li>\n<li>Go \u7684 goroutine \u5c31\u662f\u534f\u7a0b\uff0cM:N \u8c03\u5ea6\u6a21\u578b<\/li>\n<\/ul>\n<p><strong>Q40. \u4ec0\u4e48\u662f\u7528\u6237\u6001\u548c\u5185\u6838\u6001\uff1f\u7cfb\u7edf\u8c03\u7528\u7684\u5f00\u9500\u5728\u54ea\u91cc\uff1f<\/strong><\/p>\n<p>\u7b54\u9898\u8981\u70b9\uff1a<\/p>\n<ul>\n<li>\u7528\u6237\u6001\uff08Ring 3\uff09\uff1a\u53d7\u9650\u6743\u9650\uff0c\u4e0d\u80fd\u76f4\u63a5\u64cd\u4f5c\u786c\u4ef6<\/li>\n<li>\u5185\u6838\u6001\uff08Ring 0\uff09\uff1a\u5168\u6743\u9650\uff0c\u53ef\u4ee5\u64cd\u4f5c\u786c\u4ef6\u3001\u7ba1\u7406\u5185\u5b58<\/li>\n<li>\u5207\u6362\u5f00\u9500\uff1a\u4fdd\u5b58\u7528\u6237\u6001\u5bc4\u5b58\u5668 \u2192 \u5207\u6362\u5230\u5185\u6838\u6808 \u2192 \u6267\u884c\u7cfb\u7edf\u8c03\u7528 \u2192 \u6062\u590d\u7528\u6237\u6001\uff0c\u4e00\u6b21\u7ea6 200-500ns<\/li>\n<li>\u51cf\u5c11\u7cfb\u7edf\u8c03\u7528\u7684\u601d\u8def\uff1a\u6279\u91cf\u5904\u7406\uff08<code>writev<\/code> \u4e00\u6b21\u5199\u591a\u5757\uff09\u3001\u96f6\u62f7\u8d1d\uff08sendfile \u907f\u514d\u7528\u6237\u6001\u62f7\u8d1d\uff09\u3001mmap \u6620\u5c04\u5185\u5b58<\/li>\n<\/ul>\n<h2>\u7b97\u6cd5\uff1a\u5b57\u8282\u4e00\u9762\u5fc5\u624b\u6495\uff0c\u6ca1\u6709\u4f8b\u5916<\/h2>\n<p>\u5b57\u8282\u4e00\u9762\u51e0\u4e4e 100% \u4f1a\u6709\u7b97\u6cd5\u9898\uff0c\u901a\u5e38 1-2 \u9053\u3002\u96be\u5ea6\u5728 LeetCode Medium \u5de6\u53f3\uff0c\u4f46\u8981\u6c42\u4ee3\u7801\u4e0d\u51fa\u9519\uff0c\u6709\u65f6\u73b0\u573a debug\u3002\u4ee5\u4e0b\u662f\u51fa\u73b0\u9891\u7387\u6700\u9ad8\u7684\u9898\u578b\uff0c\u8003\u7684\u4e0d\u53ea\u662f\u89e3\u6cd5\uff0c\u8fd8\u6709\u300c\u4f60\u5728\u5199\u4e4b\u524d\u6709\u6ca1\u6709\u8bf4\u601d\u8def\u300d\u3002<\/p>\n<p><strong>Q41. \u624b\u6495 LRU Cache<\/strong><\/p>\n<p>\u5b57\u8282\u51fa\u73b0\u9891\u7387\u6700\u9ad8\u7684\u7b97\u6cd5\u9898\uff0c\u8981\u6c42 O(1) \u7684 get \u548c put\u3002<\/p>\n<p>\u6838\u5fc3\u601d\u8def\uff1aHashMap\uff08key \u2192 \u53cc\u5411\u94fe\u8868\u8282\u70b9\uff09+ \u53cc\u5411\u94fe\u8868\uff08\u7ef4\u62a4\u8bbf\u95ee\u987a\u5e8f\uff09<\/p>\n<ul>\n<li>get\uff1a\u4ece map \u53d6\u8282\u70b9\uff0c\u79fb\u5230\u94fe\u8868\u5934\u90e8\uff08\u8868\u793a\u6700\u8fd1\u4f7f\u7528\uff09\uff0c\u8fd4\u56de\u503c<\/li>\n<li>put\uff1akey \u5b58\u5728\u5219\u66f4\u65b0\u5e76\u79fb\u5230\u5934\u90e8\uff1b\u4e0d\u5b58\u5728\u5219\u521b\u5efa\u8282\u70b9\u63d2\u5934\u90e8\uff0c\u540c\u65f6 map \u8bb0\u5f55\u3002\u5982\u679c\u8d85\u5bb9\u91cf\uff0c\u5220\u94fe\u8868\u5c3e\u8282\u70b9\u540c\u65f6\u5220 map \u8bb0\u5f55<\/li>\n<\/ul>\n<pre><code class=\"java\">class LRUCache {\n    private final int capacity;\n    private final Map&lt;Integer, Node&gt; map;\n    private final Node head, tail; \/\/ \u54e8\u5175\u8282\u70b9\n\n    class Node {\n        int key, val;\n        Node prev, next;\n        Node(int k, int v) { key = k; val = v; }\n    }\n\n    public LRUCache(int capacity) {\n        this.capacity = capacity;\n        map = new HashMap&lt;&gt;();\n        head = new Node(0, 0);\n        tail = new Node(0, 0);\n        head.next = tail;\n        tail.prev = head;\n    }\n\n    public int get(int key) {\n        if (!map.containsKey(key)) return -1;\n        Node node = map.get(key);\n        moveToHead(node);\n        return node.val;\n    }\n\n    public void put(int key, int value) {\n        if (map.containsKey(key)) {\n            Node node = map.get(key);\n            node.val = value;\n            moveToHead(node);\n        } else {\n            Node node = new Node(key, value);\n            map.put(key, node);\n            addToHead(node);\n            if (map.size() &gt; capacity) {\n                Node tail = removeTail();\n                map.remove(tail.key);\n            }\n        }\n    }\n\n    private void moveToHead(Node node) {\n        removeNode(node);\n        addToHead(node);\n    }\n\n    private void removeNode(Node node) {\n        node.prev.next = node.next;\n        node.next.prev = node.prev;\n    }\n\n    private void addToHead(Node node) {\n        node.next = head.next;\n        node.prev = head;\n        head.next.prev = node;\n        head.next = node;\n    }\n\n    private Node removeTail() {\n        Node node = tail.prev;\n        removeNode(node);\n        return node;\n    }\n}<\/code><\/pre>\n<p><strong>Q42. \u6700\u957f\u65e0\u91cd\u590d\u5b50\u4e32\uff08\u6ed1\u52a8\u7a97\u53e3\uff09<\/strong><\/p>\n<p>\u5b57\u8282\u771f\u5b9e\u51fa\u73b0\uff0c\u8981\u6c42 O(n) \u65f6\u95f4\u590d\u6742\u5ea6\u3002<\/p>\n<p>\u6838\u5fc3\u601d\u8def\uff1a\u53cc\u6307\u9488\uff08left, right\uff09+ HashMap \u8bb0\u5f55\u5b57\u7b26\u7684\u6700\u65b0\u4f4d\u7f6e\u3002right \u904d\u5386\u5b57\u7b26\u4e32\uff0c\u82e5\u5f53\u524d\u5b57\u7b26\u5728\u7a97\u53e3\u5185\u5df2\u51fa\u73b0\uff0cleft \u8df3\u5230\u8be5\u5b57\u7b26\u4e0a\u6b21\u4f4d\u7f6e\u7684\u4e0b\u4e00\u4f4d\u3002<\/p>\n<pre><code class=\"java\">public int lengthOfLongestSubstring(String s) {\n    Map&lt;Character, Integer&gt; map = new HashMap&lt;&gt;();\n    int left = 0, maxLen = 0;\n    for (int right = 0; right &lt; s.length(); right++) {\n        char c = s.charAt(right);\n        if (map.containsKey(c) &amp;&amp; map.get(c) &gt;= left) {\n            left = map.get(c) + 1; \/\/ \u6536\u7f29\u5de6\u8fb9\u754c\n        }\n        map.put(c, right);\n        maxLen = Math.max(maxLen, right - left + 1);\n    }\n    return maxLen;\n}<\/code><\/pre>\n<p><strong>Q43. \u53cd\u8f6c\u94fe\u8868\uff08\u4ee5\u53ca\u533a\u95f4\u53cd\u8f6c [m, n]\uff09<\/strong><\/p>\n<p>\u8003\u5b98\u7248\u672c\u901a\u5e38\u662f\u300c\u53cd\u8f6c\u533a\u95f4 [m, n] \u7684\u94fe\u8868\u300d\uff0c\u800c\u4e0d\u662f\u7b80\u5355\u7684\u5168\u94fe\u8868\u53cd\u8f6c\u3002<\/p>\n<p>\u6838\u5fc3\u601d\u8def\uff1a\u7528 dummy \u8282\u70b9\uff0c\u627e\u5230\u7b2c m-1 \u4e2a\u8282\u70b9\uff0c\u7136\u540e\u5728\u533a\u95f4\u5185\u7528\u5934\u63d2\u6cd5\u9010\u4e2a\u79fb\u52a8\u8282\u70b9\u5230\u533a\u95f4\u8d77\u59cb\u4f4d\u7f6e\u3002<\/p>\n<p><strong>Q44. \u4e8c\u53c9\u6811\u7684\u5c42\u5e8f\u904d\u5386<\/strong><\/p>\n<p>BFS + \u961f\u5217\uff0c\u6bcf\u5c42\u5355\u72ec\u6536\u96c6\u3002\u8fd9\u9053\u9898\u5728\u5b57\u8282\u4e00\u9762\u91cc\u4f1a\u8fdb\u4e00\u6b65\u8ffd\u95ee\uff1a\u300c\u4e4b\u5b57\u5f62\u904d\u5386\u300d\u300c\u53ea\u6253\u5370\u53f6\u5b50\u8282\u70b9\u300d\u3002<\/p>\n<p><strong>Q45. \u5408\u5e76\u4e24\u4e2a\u6709\u5e8f\u94fe\u8868<\/strong><\/p>\n<p>\u9012\u5f52\u6216\u8fed\u4ee3\u5747\u53ef\u3002\u9012\u5f52\u5199\u6cd5\u66f4\u4f18\u96c5\u4f46\u9762\u8bd5\u65f6\u8981\u6ce8\u610f\u6808\u6df1\u5ea6\u95ee\u9898\uff1a<\/p>\n<pre><code class=\"java\">public ListNode mergeTwoLists(ListNode l1, ListNode l2) {\n    if (l1 == null) return l2;\n    if (l2 == null) return l1;\n    if (l1.val &lt;= l2.val) {\n        l1.next = mergeTwoLists(l1.next, l2);\n        return l1;\n    } else {\n        l2.next = mergeTwoLists(l1, l2.next);\n        return l2;\n    }\n}<\/code><\/pre>\n<p><strong>Q46. \u627e\u5230\u6570\u7ec4\u4e2d\u7b2c k \u5927\u7684\u5143\u7d20\uff08QuickSelect\uff09<\/strong><\/p>\n<p>TopK \u95ee\u9898\uff0c\u5b57\u8282\u559c\u6b22\u8003\u3002O(n) \u671f\u671b\u65f6\u95f4\u7684 QuickSelect\uff0c\u800c\u4e0d\u662f O(n log n) \u7684\u6392\u5e8f\u3002<\/p>\n<p>\u6838\u5fc3\u601d\u8def\uff1a\u7c7b\u4f3c\u5feb\u6392\u7684\u5206\u533a\uff0c\u4f46\u53ea\u9012\u5f52\u300ck \u6240\u5728\u7684\u90a3\u534a\u8fb9\u300d\uff1a<\/p>\n<pre><code class=\"java\">public int findKthLargest(int[] nums, int k) {\n    return quickSelect(nums, 0, nums.length - 1, nums.length - k);\n}\n\nprivate int quickSelect(int[] nums, int left, int right, int target) {\n    int pivot = partition(nums, left, right);\n    if (pivot == target) return nums[pivot];\n    return pivot &lt; target\n        ? quickSelect(nums, pivot + 1, right, target)\n        : quickSelect(nums, left, pivot - 1, target);\n}\n\nprivate int partition(int[] nums, int left, int right) {\n    int pivot = nums[right], i = left;\n    for (int j = left; j &lt; right; j++) {\n        if (nums[j] &lt;= pivot) { int t = nums[i]; nums[i++] = nums[j]; nums[j] = t; }\n    }\n    int t = nums[i]; nums[i] = nums[right]; nums[right] = t;\n    return i;\n}<\/code><\/pre>\n<p><strong>Q47. \u6700\u5927\u5b50\u6570\u7ec4\u548c\uff08Kadane \u7b97\u6cd5\uff09<\/strong><\/p>\n<p>\u7ecf\u5178\u52a8\u6001\u89c4\u5212\uff0cO(n) \u65f6\u95f4\u3002<code>dp[i]<\/code> = \u4ee5 <code>nums[i]<\/code> \u7ed3\u5c3e\u7684\u6700\u5927\u5b50\u6570\u7ec4\u548c = <code>max(nums[i], dp[i-1] + nums[i])<\/code>\uff0c\u7a7a\u95f4\u53ef\u4ee5\u538b\u7f29\u5230 O(1)\u3002<\/p>\n<p><strong>Q48. \u6709\u6548\u7684\u62ec\u53f7\uff08\u6808\uff09<\/strong><\/p>\n<p>\u6808\u5e94\u7528\uff0c\u9047\u5230\u5de6\u62ec\u53f7\u538b\u6808\uff0c\u9047\u5230\u53f3\u62ec\u53f7\u5224\u65ad\u6808\u9876\u662f\u5426\u5339\u914d\u3002\u5b57\u8282\u4f1a\u8ffd\u95ee\u300c\u8bbe\u8ba1\u4e00\u4e2a\u652f\u6301 push\u3001pop\u3001min \u7684 O(1) min \u6808\u300d\u3002<\/p>\n<p><strong>Q49. \u4e8c\u5206\u67e5\u627e\u53d8\u4f53\uff1a\u627e\u65cb\u8f6c\u6392\u5e8f\u6570\u7ec4\u7684\u6700\u5c0f\u503c<\/strong><\/p>\n<p>\u65cb\u8f6c\u6570\u7ec4\u7cfb\u5217\u662f\u5b57\u8282\u9ad8\u9891\u9898\u3002\u6838\u5fc3\u662f <code>mid<\/code> \u548c <code>right<\/code> \u6bd4\u8f83\uff1a\u5982\u679c <code>nums[mid] &gt; nums[right]<\/code>\uff0c\u6700\u5c0f\u503c\u5728\u53f3\u534a\u6bb5\uff1b\u5426\u5219\u5728\u5de6\u534a\u6bb5\uff08\u542b mid\uff09\u3002<\/p>\n<p><strong>Q50. \u52a8\u6001\u89c4\u5212\uff1a\u6700\u5c11\u5b8c\u5168\u5e73\u65b9\u6570\uff08BFS \u6216 DP \u5747\u53ef\uff09<\/strong><\/p>\n<p>\u5b57\u8282\u4e00\u9762\u771f\u5b9e\u51fa\u73b0\uff08LeetCode 279\uff09\u3002DP \u601d\u8def\uff1a<code>dp[i] = min(dp[i - j*j] + 1)<\/code>\uff0cj \u4ece 1 \u679a\u4e3e\u5230 <code>j*j &lt;= i<\/code>\u3002<\/p>\n<h2>\u9ad8\u9891 FAQ<\/h2>\n<p><strong>Q\uff1a\u5b57\u8282\u4e00\u9762\u7b97\u6cd5\u51e0\u9053\u9898\uff0c\u4ec0\u4e48\u96be\u5ea6\uff1f<\/strong><\/p>\n<p>\u4e00\u822c 1-2 \u9053\uff0cLeetCode Medium \u4e3a\u4e3b\uff0c\u5c11\u90e8\u5206 Hard\uff08\u4e8c\u53c9\u6811\u7cfb\u5217\u3001\u52a8\u89c4\uff09\u3002\u4f46\u5b57\u8282\u9762\u8bd5\u5b98\u559c\u6b22\u5728\u4f60\u5199\u5b8c\u540e\u8ffd\u52a0\u7ea6\u675f\u6216\u53d8\u5f62\uff0c\u300c\u5982\u679c\u8f93\u5165\u6709\u91cd\u590d\u5143\u7d20\u5462\u300d\u300c\u5982\u679c\u8981\u6c42 O(1) \u7a7a\u95f4\u5462\u300d\uff0c\u8fd9\u624d\u662f\u771f\u6b63\u7b5b\u4eba\u7684\u90e8\u5206\u3002\u5199\u5b8c\u5c31\u6ee1\u8db3\u662f\u4e0d\u591f\u7684\uff0c\u8981\u4e3b\u52a8\u8bf4\u51fa\u8fb9\u754c\u60c5\u51b5\u548c\u590d\u6742\u5ea6\u5206\u6790\u3002<\/p>\n<p><strong>Q\uff1a\u4e00\u9762\u591a\u957f\u65f6\u95f4\uff0c\u77e5\u8bc6\u70b9\u95ee\u591a\u5c11\uff1f<\/strong><\/p>\n<p>\u901a\u5e38 45-60 \u5206\u949f\u3002\u7ed3\u6784\u901a\u5e38\u662f\uff1a5 \u5206\u949f\u81ea\u6211\u4ecb\u7ecd + \u9879\u76ee\u6df1\u6316 \u2192 20 \u5206\u949f\u77e5\u8bc6\u70b9\uff08\u9009 2-3 \u4e2a\u9886\u57df\uff0c\u6bcf\u4e2a\u9886\u57df 3-4 \u9053\u8ffd\u95ee\uff09 \u2192 20 \u5206\u949f\u7b97\u6cd5 \u2192 5 \u5206\u949f\u53cd\u95ee\u3002\u77e5\u8bc6\u70b9\u4e0d\u662f\u4e00\u9053\u9053\u987a\u5e8f\u8fc7\uff0c\u800c\u662f\u9009\u51e0\u4e2a\u70b9\u6df1\u6316\u5230\u5e95\u3002<\/p>\n<p><strong>Q\uff1a\u9879\u76ee\u7ecf\u5386\u548c\u77e5\u8bc6\u70b9\u54ea\u4e2a\u66f4\u91cd\u8981\uff1f<\/strong><\/p>\n<p>\u90fd\u91cd\u8981\uff0c\u4f46\u9879\u76ee\u662f\u300c\u5dee\u5f02\u5316\u300d\u7684\u5730\u65b9\u3002\u77e5\u8bc6\u70b9\u56de\u7b54\u5dee\u4e0d\u591a\uff0c\u9762\u8bd5\u5b98\u4f1a\u5728\u9879\u76ee\u4e0a\u627e\u533a\u5206\u5ea6\u2014\u2014\u300c\u4f60\u8bf4\u4f60\u7528\u4e86\u5206\u5e03\u5f0f\u9501\uff0c\u5177\u4f53\u662f\u4ec0\u4e48\u573a\u666f\uff0c\u4e3a\u4ec0\u4e48\u4e0d\u7528 DB \u4e50\u89c2\u9501\u300d\u3002\u6ca1\u6709\u5b9e\u9645\u9879\u76ee\u91cc\u7528\u8fc7\u7684\u6280\u672f\uff0c\u80cc\u518d\u591a\u516b\u80a1\u4e5f\u5f88\u5bb9\u6613\u88ab\u8ffd\u95ee\u9732\u9985\u3002<\/p>\n<p><strong>Q\uff1a\u7b54\u9898\u65f6\u53d1\u73b0\u67d0\u4e2a\u539f\u7406\u6ca1\u80cc\u5230\u600e\u4e48\u529e\uff1f<\/strong><\/p>\n<p>\u5b9e\u8bdd\u5b9e\u8bf4\u300c\u8fd9\u4e2a\u7ec6\u8282\u6211\u4e0d\u592a\u786e\u5b9a\uff0c\u6211\u7684\u7406\u89e3\u662f XX\uff0c\u4f46\u53ef\u80fd\u6709\u504f\u5dee\u300d\uff0c\u7136\u540e\u8bf4\u51fa\u4f60\u80fd\u63a8\u5bfc\u51fa\u6765\u7684\u90e8\u5206\u3002\u6bd4\u300c\u7f16\u4e00\u4e2a\u4e0d\u786e\u5b9a\u7684\u7b54\u6848\u300d\u597d\u5f97\u591a\u2014\u2014\u5b57\u8282\u9762\u8bd5\u5b98\u8ffd\u51e0\u53e5\u5c31\u80fd\u5224\u65ad\u4f60\u662f\u5728\u80cc\u4e66\u8fd8\u662f\u771f\u6b63\u7406\u89e3\u3002<\/p>\n<p><strong>Q\uff1aSpring Boot \u76f8\u5173\u77e5\u8bc6\u9762\u5417\uff1f<\/strong><\/p>\n<p>\u4e00\u9762\u901a\u5e38\u4e0d\u4e3b\u52a8\u8003 Spring\uff0c\u4f46\u5982\u679c\u4f60\u7b80\u5386\u4e0a\u5199\u4e86 Spring \u9879\u76ee\uff0c\u4f1a\u501f\u6b64\u8ffd\u95ee\u300cBean \u7684\u751f\u547d\u5468\u671f\u300d\u300c\u5faa\u73af\u4f9d\u8d56\u600e\u4e48\u89e3\u51b3\u300d\u300cSpring \u4e8b\u52a1\u5931\u6548\u7684\u573a\u666f\u300d\u3002\u6240\u4ee5\u5199\u8fdb\u7b80\u5386\u7684\u6846\u67b6\u8981\u786e\u4fdd\u80fd\u8bf4\u6e05\u695a\u539f\u7406\u3002<\/p>\n<h2>\u603b\u7ed3<\/h2>\n<p>\u5b57\u8282\u4e00\u9762\u7684\u901a\u8fc7\u7387\u4e0d\u9ad8\uff0c\u4e0d\u662f\u56e0\u4e3a\u9898\u76ee\u8d85\u7eb2\uff0c\u800c\u662f\u56e0\u4e3a\u5927\u591a\u6570\u4eba\u51c6\u5907\u7684\u662f\u300c\u80cc\u7b54\u6848\u300d\u800c\u4e0d\u662f\u300c\u7406\u89e3\u8bbe\u8ba1\u300d\u3002\u8fd9 50 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