{"id":1686,"date":"2020-08-30T23:30:22","date_gmt":"2020-08-30T15:30:22","guid":{"rendered":"https:\/\/blog.dynox.cn\/?p=1686"},"modified":"2023-08-07T01:35:23","modified_gmt":"2023-08-06T17:35:23","slug":"cache%e4%b8%ba%e4%bb%80%e4%b9%88%e8%83%bd%e6%8f%90%e5%8d%87%e6%80%a7%e8%83%bd","status":"publish","type":"post","link":"https:\/\/blog.dynox.cn\/?p=1686","title":{"rendered":"Cache\u4e3a\u4ec0\u4e48\u80fd\u63d0\u5347\u6027\u80fd"},"content":{"rendered":"

1. Cache\u7684\u5bb9\u91cf\u8bbe\u8ba1<\/h1>\n

\u4e0a\u7bc7\u6587\u7ae0\u4e2d\u4ecb\u7ecd\u5230CPU Cache\u662f\u5206\u7ea7\u7684\uff0cL1 Cache\u662f\u96c6\u6210\u5728Core\u5185\u90e8\u7684\uff0cL2\u5219\u662f\u7d27\u8d34\u7740Core\uff0c\u800cL3\u662f\u591a\u4e2aCore\u5171\u4eab\u7684\u3002\u79bbCore\uff08\u6d41\u6c34\u7ebf\uff09\u8d8a\u8fd1\u7684\u5206\u7ea7\u901f\u5ea6\u8d8a\u5feb\uff0c\u4f46\u5bb9\u91cf\u4e5f\u66f4\u5c0f\uff0c\u5e76\u4e14\u9020\u4ef7\u6108\u8d35\u3002Cache\u7684\u5b9e\u73b0\u91c7\u7528\u4e86\u9ad8\u901f\u7684SRAM\u7535\u8def (\u9759\u6001\u968f\u673a\u5b58\u53d6\u5b58\u50a8\u5668: Static Random-Access Memory)\uff0cSRAM\u76f8\u5bf9DRAM (\u52a8\u6001\u968f\u673a\u5b58\u53d6\u5b58\u50a8\u5668: Dynamic Random Access Memory)\u8981\u590d\u6742\u548c\u5e9e\u5927\u7684\u591a\uff0c\u5373\u4f7f\u4e0d\u8003\u8651\u6210\u672c\u80fd\u505a\u5230\u65e0\u9650\u589e\u5927\uff0c\u4f46\u56e0\u4e3a\u7535\u8def\u590d\u6742\u5ea6\u7684\u63d0\u5347\u5176\u6027\u80fd\u5373\u8bbf\u95ee\u901f\u5ea6\u5fc5\u7136\u4f1a\u4e0b\u964d\uff0c\u53e6\u5916\u4e5f\u4f1a\u4f7f\u5f97CPU\u7684\u9762\u79ef\u6025\u901f\u81a8\u80c0\u3002\u6700\u7ec8\uff0cCPU\u7684\u6bcf\u4e00\u7ea7Cache\u7684\u5bb9\u91cf\u90fd\u662f\u5728\u8bbe\u8ba1\u4e4b\u521d\u8003\u8651\u5404\u65b9\u9762\u56e0\u7d20\u6298\u4e2d\u540e\u7684\u7ed3\u679c\uff08trade-off\uff09\u3002\u4e0b\u56fe\u662fAMD Zen\u7684CCX\u7684die shot[\u6765\u6e90\uff1a1. Zen - Microarchitectures - AMD]\uff0c\u4ece\u56fe\u4e2d\u6211\u4eec\u5c31\u80fd\u770b\u4e2dL2\u53caL3 Cache\u5360\u636e\u4e86\u5f88\u5927\u4e00\u90e8\u5206\u7684\u9762\u79ef\uff1a\n\"AMD<\/p>\n

\u4e00\u822c\u800c\u8a00L1 Cache\u7ea6\u51e0\u5341K\uff0cL2\u5219\u662f\u51e0\u767eK\uff0cL3\u662f\u51e0M\u6216\u51e0\u5341\u3001\u51e0\u767eM\uff0c\u4f46\u76f8\u6bd4\u8f83\u5185\u5b58\u52a8\u4e0d\u52a8\u51e0\u5341G\u7684\u5927\u5c0f\u6765\u8bf4\u8fd8\u662f\u5c0f\u4e86\u592a\u591a\uff0c\u6839\u672c\u4e0d\u5728\u4e00\u4e2a\u6570\u91cf\u7ea7\u4e0a\u3002\u90a3\u4e48\u95ee\u9898\u6765\u4e86\uff1aCache\u5bb9\u91cf\u6bd4\u5185\u5b58\u5c0f\u4e86\u592a\u591a\uff0c\u4e3a\u4ec0\u4e48\u6839\u672c\u4e0d\u5728\u4e00\u4e2a\u6570\u636e\u91cf\u7ea7\u7684Cache\u80fd\u591f\u5927\u526f\u5ea6\u63d0\u5347\u7cfb\u7edf\u6027\u80fd\uff1f<\/p>\n

2. \u5c40\u90e8\u6027\u539f\u7406 (Principle of Locality)<\/h1>\n

\u7b80\u8a00\u4e4b\uff0c\u7a0b\u5e8f\u503e\u5411\u4e8e\u8bbf\u95ee\uff08\u6216\u6267\u884c\uff09\u521a\u521a\u8bbf\u95ee\u8fc7\u7684\u6570\u636e\uff08\u6267\u884c\u8fc7\u7684\u6307\u4ee4\uff09\u6216\u4e0e\u4e4b\u76f8\u4e34\u8fd1\u7684\u6570\u636e\uff08\u6307\u4ee4\uff09<\/p>\n

2.1 \u65f6\u95f4\u5c40\u90e8\u6027 (Temporal locality):<\/h2>\n

\u521a\u521a\u88ab\u8bbf\u95ee\u7684\u5730\u5740\uff08\u6570\u636e\uff09\u5728\u672a\u6765\u6709\u5f88\u5927\u7684\u53ef\u80fd\u6027\u88ab\u518d\u6b21\u8bbf\u95ee\uff0c\u5373\u7528\u8fc7\u7684\u6570\u636e\u53ef\u80fd\u4f1a\u518d\u6b21\u88ab\u7528\u5230<\/p>\n

2.2 \u7a7a\u95f4\u5c40\u90e8\u6027 (Spatial locality):<\/h2>\n

\u521a\u521a\u88ab\u8bbf\u95ee\u7684\u5730\u5740\u7684\u4e34\u8fd1\u4f4d\u7f6e\u5728\u672a\u6765\u6709\u5f88\u5927\u7684\u53ef\u80fd\u88ab\u8bbf\u95ee\uff0c\u4ee5\u6570\u7ec4D[]\u4e3a\u4f8b\uff0c\u5f53\u524d\u8bbf\u95ee\u7684\u662fD[i]\uff0c\u90a3\u4e48D[i+1]\u6709\u5f88\u5927\u7684\u53ef\u80fd\u5c06\u88ab\u8bbf\u95ee<\/p>\n

2.3 \u7b97\u6cd5\u5c40\u90e8\u6027\uff1a<\/h2>\n

\u7a0b\u5e8f\u4ee3\u7801\u4e5f\u9075\u5b882\/8\u6cd5\u5219\uff0c\u5373\u5e15\u7d2f\u6258\u6cd5\u5219\uff08Pareto principle\uff0c\u4ea6\u79f0\u5173\u952e\u5c11\u6570\u6cd5\u5219\uff09\uff0c80%\u7684\u65f6\u95f4\u90fd\u662f\u5728\u6267\u884c20%\u7684\u4ee3\u7801<\/p>\n

\u6b63\u662f\u56e0\u4e3a\u5c40\u90e8\u6027\u539f\u7406\uff0c\u5c11\u91cf\u7684Cache\u5927\u5927\u51cf\u5c11\u4e86\u6570\u636e\u7684\u8bbf\u95ee\u5ef6\u8fdf\uff0c\u4ece\u800c\u63d0\u5347\u4e86\u6574\u4f53\u6027\u80fd\u3002<\/p>\n

3. Cache\u7684\u653e\u5927\u6548\u5e94<\/h1>\n

\u5148\u6765\u8003\u8651\u4e00\u4e2a\u95ee\u9898\uff1aCache\u547d\u4e2d\u7387(Cache Hit) 99%\u4e0e98%\u7684\u5dee\u522b\u4f1a\u6709\u591a\u5927\uff1f\u4ece\u6570\u503c\u4e0a\u6765\u770b\u4e8c\u8005\u672c\u8eab\u4ec5\u76f8\u5dee1%\uff0c\u6027\u80fd\u4e0a\u6700\u7ec8\u80fd\u6709\u591a\u5927\u5dee\u522b\u5462\uff1f<\/p>\n

\u5047\u8bbe\u547d\u4e2dL1\u7684\u5ef6\u65f6\u4e3a4 cycles\uff0c\u4e0d\u547d\u4e2d\u7684\u8bdd\u9700\u8981\u4ece\u5185\u5b58\u4e2d\u8bfb\u53d6\u6570\u636e\u7684\u5ef6\u65f6\u4e3a150 cycles\uff0c\u90a3\u4e48\uff1a\n99%\u547d\u4e2d\u7387\u7684\u60c5\u51b5: 0.99 4 + 0.01 <\/em> 150 = 5.46\n98%\u547d\u4e2d\u7387\u7684\u60c5\u51b5: 0.98 4 + 0.02 <\/em> 150 = 6.92<\/p>\n

\u540e\u8005\u6bd4\u524d\u8005\u7684\u5ef6\u65f6\u591a\u4e86(6.92 - 5.46) \/ 5.46 = 26.7% \u4e4b\u591a\u3002\u6362\u621095%\u7684\u547d\u4e2d\u7387\u7684\u8bdd\uff0c\u5ef6\u65f6\u5c06\u9ad8\u8fbe99%\u547d\u4e2d\u7387\u65f6\u7684\u4e00\u500d\u4e4b\u591a\u3002\u7531\u6b64\u770b\u6765\uff0c\u4e0d\u547d\u4e2d\uff08Cache Miss\uff09\u6240\u5e26\u7684\u6027\u80fd\u60e9\u7f5a\u5de8\u5927\uff0c\u8fd9\u4e5f\u9884\u793a\u4e86\u672a\u6765Cache\u53d1\u5c55\u7684\u8d8b\u52bf\uff0c\u5373\u5bb9\u91cf\u5c06\u8d8a\u6765\u8d8a\u5927\uff0c\u62e5\u6709GB\u7ea7Cache\u5bb9\u91cf\u7684CPU\u5c06\u6307\u65e5\u53ef\u5f85\uff0c\u53e6\u5916\u589e\u52a0L4\u5206\u7ea7\u4e5f\u5c06\u662f\u4e0d\u53ef\u907f\u514d\u7684\uff0c\u6709\u5174\u8da3\u7684\u8bfb\u8005\u53ef\u8fdb\u4e00\u6b65\u53c2\u9605 [2. The Next Platform: Cache Is King]\u3002<\/p>\n

4. Cache Miss\u7684\u539f\u56e0<\/h1>\n

\u524d\u9762\u8bf4\u4e86Cache Miss\u7684\u60e9\u7f5a\uff0c\u4e0b\u9762\u8bf4\u4e00\u4e0b\u4f1a\u5bfc\u81f4Cache Miss\u7684\u56e0\u7d20\uff0c\u53ef\u4ee5\u7b80\u5355\u5f52\u7eb3\u4e3a3C:<\/p>\n

    \n
  1. Cold (Compulsory) Miss\uff1a \u7b2c\u4e00\u6b21\u8bbf\u95ee\u6570\u636e\u65f6\uff0c\u6570\u636e\u6839\u672c\u4e0d\u5728Cache\u4e2d<\/li>\n
  2. Conflict Miss\uff1a \u56e0\u51b2\u7a81\u5bfc\u81f4Cache Line\u88ab\u9a71\u9010\u51faCache\uff0c\u4e0a\u4e00\u7bc7\u6587\u7ae0\u4e2d\u63d0\u5230\u4e86\u76f8\u5173\u7684\u65b9\u6cd5\uff0c\u5982Evict(\u9a71\u9010)\u3001Prime(\u88c5\u586b)\u7b49\uff0c\u5f53\u7136\u51b2\u7a81\u6240\u5bfc\u81f4\u7684Cache Miss\u53ea\u9488\u5bf9\u7ec4\u76f8\u8054\u7684Cache\u7ed3\u6784\uff08\u76f4\u63a5\u6620\u5c04\u53ef\u4ee5\u8ba4\u4e3a\u662f\u5355\u8def\u7ec4\u76f8\u8054\uff09\uff0c\u800c\u5168\u76f8\u8054\u7684Cache\u7ed3\u6784\u662f\u6ca1\u6709Conflict Miss\u7684\uff0c\u540e\u7eed\u8fd8\u4f1a\u9488\u5bf9\u6b64\u8bfe\u9898\u505a\u8be6\u7ec6\u7684\u4ecb\u7ecd<\/li>\n
  3. Capacity Miss\uff1a Cache\u7684\u5bb9\u91cf\u6bd5\u7adf\u6709\u9650\uff0c\u5982\u679c\u7a0b\u5e8f\u786e\u5b9e\u9700\u8981\u5bc6\u96c6\u8bbf\u95ee\u5927\u91cf\u5185\u5b58\u65f6\uff0cCache\u5fc5\u7136\u662f\u4e0d\u591f\u7684<\/li>\n<\/ol>\n

    \u5728\u6307\u5b9a\u7684CPU\u786c\u4ef6\u4e0a\u5982\u679c\u60f3\u63d0\u5347Cache Hit\u7684\u8bdd\u5c31\u8981\u4ece\u8fd9\u51e0\u4e2a\u56e0\u7d20\u4e0a\u7740\u624b\uff0c\u5982\u901a\u8fc7\u786c\u4ef6\u9884\u53d6\u4ee5\u51cf\u5c11Cold Miss\uff0c\u901a\u8fc7\u7a0b\u5e8f\u7b97\u6cd5\u6539\u8fdb\u53ca\u7ed3\u6784\u91cd\u7ec4\u53ef\u51cf\u5c112\u548c3\u6240\u5e26\u6765\u7684Cache Miss\u7684\u53d1\u751f\u6982\u7387\uff0c\u672c\u6587\u5148\u70b9\u5230\u4e3a\u6b62\uff0c\u540e\u9762\u5c06\u8fdb\u884c\u8be6\u7ec6\u62c6\u89e3\u3002<\/p>\n

    5. \u53c2\u8003\u8d44\u6599<\/h1>\n
      \n
    1. wikichip: Zen - Microarchitectures - AMD<\/a><\/li>\n
    2. The Next Platform: Cache Is King<\/a><\/li>\n<\/ol><\/div>","protected":false},"excerpt":{"rendered":"

      1. Cache\u7684\u5bb9\u91cf\u8bbe\u8ba1 \u4e0a\u7bc7\u6587\u7ae0\u4e2d\u4ecb\u7ecd\u5230CPU Cache\u662f\u5206\u7ea7\u7684\uff0cL1 Cache\u662f\u96c6\u6210\u5728Core\u5185\u90e8\u7684 […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"ngg_post_thumbnail":0,"footnotes":""},"categories":[9],"tags":[626,622,627,628],"views":773,"_links":{"self":[{"href":"https:\/\/blog.dynox.cn\/index.php?rest_route=\/wp\/v2\/posts\/1686"}],"collection":[{"href":"https:\/\/blog.dynox.cn\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/blog.dynox.cn\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/blog.dynox.cn\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/blog.dynox.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=1686"}],"version-history":[{"count":1,"href":"https:\/\/blog.dynox.cn\/index.php?rest_route=\/wp\/v2\/posts\/1686\/revisions"}],"predecessor-version":[{"id":1687,"href":"https:\/\/blog.dynox.cn\/index.php?rest_route=\/wp\/v2\/posts\/1686\/revisions\/1687"}],"wp:attachment":[{"href":"https:\/\/blog.dynox.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=1686"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/blog.dynox.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=1686"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/blog.dynox.cn\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=1686"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}