{"id":3862,"date":"2025-07-12T13:25:11","date_gmt":"2025-07-12T05:25:11","guid":{"rendered":"https:\/\/www.laixuexila.com\/?p=3862"},"modified":"2025-07-12T13:25:11","modified_gmt":"2025-07-12T05:25:11","slug":"longadder-%e5%a6%82%e4%bd%95%e5%9c%a8%e9%ab%98%e5%b9%b6%e5%8f%91%e4%b8%8b%e7%94%a8-cas-%e5%ae%9e%e7%8e%b0%e6%af%94-atomicinteger-%e6%9b%b4%e9%ab%98%e6%80%a7%e8%83%bd%ef%bc%9f","status":"publish","type":"post","link":"https:\/\/www.laixuexila.com\/index.php\/2025\/07\/12\/longadder-%e5%a6%82%e4%bd%95%e5%9c%a8%e9%ab%98%e5%b9%b6%e5%8f%91%e4%b8%8b%e7%94%a8-cas-%e5%ae%9e%e7%8e%b0%e6%af%94-atomicinteger-%e6%9b%b4%e9%ab%98%e6%80%a7%e8%83%bd%ef%bc%9f\/","title":{"rendered":"LongAdder \u5982\u4f55\u5728\u9ad8\u5e76\u53d1\u4e0b\u7528 CAS \u5b9e\u73b0\u6bd4 AtomicInteger \u66f4\u9ad8\u6027\u80fd\uff1f"},"content":{"rendered":"\n<p>\u8fd9\u662f\u4e00\u4e2a\u975e\u5e38\u5178\u578b\u4e5f\u975e\u5e38\u91cd\u8981\u7684\u5e76\u53d1\u6027\u80fd\u4f18\u5316\u95ee\u9898\u3002<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">1\u3001\u7b80\u8981\u7ed3\u8bba\uff1a<\/h2>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p><code>LongAdder<\/code> \u662f <code>AtomicLong<\/code> \u7684\u6027\u80fd\u589e\u5f3a\u7248\uff0c\u5728<strong>\u9ad8\u5e76\u53d1\u573a\u666f\u4e0b\u6bd4 AtomicLong \u66f4\u9ad8\u6548<\/strong>\uff0c\u5176\u6838\u5fc3\u662f\uff1a<strong>\u4f7f\u7528\u5206\u6bb5\uff08Striped\uff09\u601d\u60f3 + CAS \u64cd\u4f5c<\/strong>\uff0c\u907f\u514d\u5927\u91cf\u7ebf\u7a0b\u4e89\u62a2\u540c\u4e00\u4e2a\u53d8\u91cf\u3002<\/p>\n<\/blockquote>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">2\u3001\u4e3a\u4ec0\u4e48 AtomicLong \u4f1a\u6210\u4e3a\u6027\u80fd\u74f6\u9888\uff1f<\/h2>\n\n\n\n<p><code>AtomicLong<\/code> \u7684\u5e95\u5c42\u5b9e\u73b0\u662f\u57fa\u4e8e <strong>CAS\uff08Compare-And-Swap\uff09<\/strong> \u7684\uff1a<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>public final long incrementAndGet() {\n    for (;;) {\n        long current = get();\n        long next = current + 1;\n        if (compareAndSet(current, next))\n            return next;\n    }\n}<\/code><\/pre>\n\n\n\n<h3 class=\"wp-block-heading\">\u26a0\ufe0f \u95ee\u9898\uff1a<\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u6240\u6709\u7ebf\u7a0b\u90fd\u5728\u4e89\u62a2\u4e00\u4e2a\u53d8\u91cf\uff08\u5982 <code>count<\/code>\uff09<\/li>\n\n\n\n<li>\u5e76\u53d1\u9ad8\u65f6\uff0c<code>CAS<\/code> \u6210\u529f\u7387\u53d8\u4f4e\uff0c\u5927\u91cf\u81ea\u65cb\uff0c<strong>CPU \u5f00\u9500\u5927<\/strong><\/li>\n<\/ul>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">3\u3001LongAdder \u7684\u8bbe\u8ba1\u6838\u5fc3\uff1a\u5206\u6bb5\u8ba1\u6570<\/h2>\n\n\n\n<h3 class=\"wp-block-heading\">\ud83d\udc49 \u7c7b\u4f3c\u201c\u5206\u533a\u7edf\u8ba1\u201d\uff1a\u628a\u4e00\u4e2a\u53d8\u91cf\u62c6\u6210\u591a\u4e2a\uff0c\u5206\u644a\u7ade\u4e89\u538b\u529b<\/h3>\n\n\n\n<pre class=\"wp-block-code\"><code>+-----------+-----------+-----------+-----------+\n| Cell&#91;0]   | Cell&#91;1]   | Cell&#91;2]   | ...       |\n|   5       |   3       |   4       |           |\n+-----------+-----------+-----------+-----------+<\/code><\/pre>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u6bcf\u4e2a\u7ebf\u7a0b\u5bf9\u4e0d\u540c\u7684 Cell \u64cd\u4f5c<\/li>\n\n\n\n<li>\u6700\u540e\u901a\u8fc7\u6240\u6709 Cell \u7684\u503c + \u57fa\u7840\u503c\uff08<code>base<\/code>\uff09\u6c42\u548c\u5f97\u51fa\u603b\u503c<\/li>\n<\/ul>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">4\u3001\u6e90\u7801\u7ed3\u6784\uff08\u7b80\u5316\uff09<\/h2>\n\n\n\n<pre class=\"wp-block-code\"><code>public class LongAdder extends Striped64 {\n    \/\/ \u5206\u6bb5\u6570\u7ec4\uff08\u61d2\u521d\u59cb\u5316\uff09\n    transient volatile Cell&#91;] cells;\n\n    \/\/ \u4f4e\u7ade\u4e89\u65f6\u4f7f\u7528\u7684\u57fa\u7840\u503c\n    transient volatile long base;\n}<\/code><\/pre>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">5\u3001increment() \u65b9\u6cd5\u5b9e\u73b0\u903b\u8f91\uff08\u7b80\u5316\uff09<\/h2>\n\n\n\n<pre class=\"wp-block-code\"><code>public void increment() {\n    Cell&#91;] as; long b; int m, h;\n    if ((as = cells) != null || !casBase(b = base, b + 1)) {\n        boolean uncontended = true;\n        if (as == null || (m = as.length - 1) &lt; 0 ||\n            as&#91;h &amp; m] == null || !(uncontended = as&#91;h &amp; m].cas(v, v + 1)))\n            longAccumulate(1L, null, uncontended);\n    }\n}<\/code><\/pre>\n\n\n\n<h3 class=\"wp-block-heading\">\u26d3\ufe0f \u89e3\u91ca\u6d41\u7a0b\uff1a<\/h3>\n\n\n\n<ol class=\"wp-block-list\">\n<li>\u4f18\u5148\u5c1d\u8bd5 <code>CAS<\/code> \u589e\u52a0 <code>base<\/code>\uff08\u4f4e\u5e76\u53d1\u4e0b\u8d70\u8fd9\u91cc\uff09<\/li>\n\n\n\n<li>\u5982\u679c\u5931\u8d25\uff0c\u5c1d\u8bd5\u5bf9\u5f53\u524d\u7ebf\u7a0b\u7684 Cell \u4f4d\u7f6e\u8fdb\u884c <code>CAS<\/code> \u589e\u52a0<\/li>\n\n\n\n<li>\u5982\u679c\u8fd8\u5931\u8d25\uff0c\u8bf4\u660e\u7ade\u4e89\u4e25\u91cd\uff0c\u8c03\u7528 <code>longAccumulate()<\/code>\uff1a<\/li>\n<\/ol>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u521d\u59cb\u5316\u6216\u6269\u5c55 <code>cells<\/code> \u6570\u7ec4<\/li>\n\n\n\n<li>\u91cd\u8bd5\u63d2\u5165\u5230\u65b0\u7684 Cell \u69fd\u4f4d<\/li>\n<\/ul>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">6\u3001\u6c42\u548c\u64cd\u4f5c\uff08sum()\uff09<\/h2>\n\n\n\n<pre class=\"wp-block-code\"><code>public long sum() {\n    Cell&#91;] as = cells;\n    long sum = base;\n    if (as != null) {\n        for (Cell a : as) {\n            if (a != null)\n                sum += a.value;\n        }\n    }\n    return sum;\n}<\/code><\/pre>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p>\u26a0\ufe0f <code>sum()<\/code> <strong>\u4e0d\u662f\u539f\u5b50\u64cd\u4f5c<\/strong>\uff0c\u4ec5\u505a\u8fd1\u4f3c\u7edf\u8ba1\uff08\u9002\u7528\u4e8e\u7edf\u8ba1\u8ba1\u6570\u3001QPS\u3001\u8bf7\u6c42\u91cf\u7b49\uff09<\/p>\n<\/blockquote>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">7\u3001LongAdder vs AtomicLong \u6027\u80fd\u5bf9\u6bd4<\/h2>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><thead><tr><th>\u6307\u6807<\/th><th><code>AtomicLong<\/code><\/th><th><code>LongAdder<\/code><\/th><\/tr><\/thead><tbody><tr><td>CAS \u91cd\u8bd5\u5f00\u9500<\/td><td>\u9ad8\uff08\u96c6\u4e2d\u5728\u5355\u53d8\u91cf\uff09<\/td><td>\u4f4e\uff08\u5206\u6bb5\u5206\u6563\uff09<\/td><\/tr><tr><td>\u9ad8\u5e76\u53d1\u6027\u80fd<\/td><td>\u4e00\u822c\uff0c\u5bb9\u6613\u4e89\u62a2<\/td><td>\u4f18\u79c0\uff0c\u907f\u514d\u70ed\u70b9\u7ade\u4e89<\/td><\/tr><tr><td>\u7a7a\u95f4\u5f00\u9500<\/td><td>\u4f4e<\/td><td>\u7a0d\u9ad8\uff08\u591a\u4e2a <code>Cell<\/code> \u5360\u5185\u5b58\uff09<\/td><\/tr><tr><td>\u7cbe\u5ea6<\/td><td>\u7cbe\u786e<\/td><td>\u9ad8\u5e76\u53d1\u4e0b\u53ef\u80fd\u8fd1\u4f3c\uff08\u975e\u539f\u5b50\uff09<\/td><\/tr><tr><td>\u9002\u7528\u573a\u666f<\/td><td>\u4f4e\u5e76\u53d1\/\u7cbe\u51c6\u8ba1\u6570<\/td><td>\u9ad8\u5e76\u53d1\/\u7edf\u8ba1\u578b\u8ba1\u6570\uff08QPS\uff09<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">8\u3001\u5b9e\u9645\u4f7f\u7528\u5efa\u8bae<\/h2>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><thead><tr><th>\u5e94\u7528\u573a\u666f<\/th><th>\u63a8\u8350\u4f7f\u7528<\/th><\/tr><\/thead><tbody><tr><td>Web \u8bbf\u95ee\u8ba1\u6570\u5668<\/td><td>\u2705 <code>LongAdder<\/code>\uff08\u541e\u5410\u91cf\u66f4\u9ad8\uff09<\/td><\/tr><tr><td>\u5e76\u53d1\u9650\u6d41\u7edf\u8ba1<\/td><td>\u2705 <code>LongAdder<\/code><\/td><\/tr><tr><td>\u4ea4\u6613\u7cfb\u7edf\u8ba1\u6570\uff08\u9700\u7cbe\u786e\uff09<\/td><td>\u274c \u7528 <code>AtomicLong<\/code> \u6216\u52a0\u9501<\/td><\/tr><tr><td>\u8ba1\u91cf\u6307\u6807\u4e0a\u62a5\uff08Prometheus\uff09<\/td><td>\u2705 <code>LongAdder<\/code><\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">9\u3001\u53c2\u8003\u94fe\u63a5<\/h2>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\ud83d\udd17 <a href=\"https:\/\/github.com\/openjdk\/jdk\/blob\/master\/src\/java.base\/share\/classes\/java\/util\/concurrent\/atomic\/LongAdder.java\">Java \u6e90\u7801\uff1aLongAdder<\/a><\/li>\n\n\n\n<li>\ud83d\udd17 <a href=\"http:\/\/gee.cs.oswego.edu\/dl\/papers\/striped.pdf\">JDK Concurrency \u539f\u59cb\u8bbe\u8ba1\u8005 Doug Lea \u7684 Striped64 \u8bba\u6587<\/a><\/li>\n\n\n\n<li>\ud83d\udd17 <a href=\"https:\/\/docs.oracle.com\/javase\/8\/docs\/api\/java\/util\/concurrent\/atomic\/LongAdder.html\">\u5b98\u65b9\u6587\u6863\uff1a<code>LongAdder<\/code><\/a><\/li>\n\n\n\n<li>\ud83d\udd17 <a href=\"https:\/\/juejin.cn\/post\/6844904130276294664\">\u963f\u91cc P8 \u5206\u6790\uff1aLongAdder \u662f\u600e\u4e48\u505a\u5230\u6bd4 AtomicLong \u5feb\u7684<\/a><\/li>\n<\/ul>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">10\u3001\u603b\u7ed3\u8bb0\u5fc6\u53e3\u8bc0<\/h2>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p><strong>AtomicLong \u9ad8\u7ade\u4e89\u6613\u74f6\u9888\uff0cLongAdder \u5206\u6bb5\u5de7\u907f\u950b\uff1bbase \u4f18\u5148\uff0ccell \u5206\u644a\uff0c\u8fd1\u4f3c\u7edf\u8ba1\u5feb\u5982\u98ce\u3002<\/strong><\/p>\n<\/blockquote>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<p>\u66f4\u591a\u8be6\u7ec6\u5185\u5bb9\u8bf7\u5173\u6ce8\u5176\u4ed6\u76f8\u5173\u6587\u7ae0\uff01<\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u8fd9\u662f\u4e00\u4e2a\u975e\u5e38\u5178\u578b\u4e5f\u975e\u5e38\u91cd\u8981\u7684\u5e76\u53d1\u6027\u80fd\u4f18\u5316\u95ee\u9898\u3002 1\u3001\u7b80\u8981\u7ed3\u8bba\uff1a LongAdder \u662f AtomicLong  [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":3863,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[86],"tags":[],"class_list":["post-3862","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-java-"],"_links":{"self":[{"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/posts\/3862","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/comments?post=3862"}],"version-history":[{"count":1,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/posts\/3862\/revisions"}],"predecessor-version":[{"id":3864,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/posts\/3862\/revisions\/3864"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/media\/3863"}],"wp:attachment":[{"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/media?parent=3862"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/categories?post=3862"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/tags?post=3862"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}