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大目

2020-07-13

您好，很棒的问题，看来是一位爱动脑筋，热爱技术的童鞋^_^

阈值如下：

Tier2CompileThreshold
Tier3CompileThreshold
Tier4CompileThreshold

课上没有列出每一层的阈值。但学到后面一些的章节，理论上，大家就会有能力自己查找出想要的JVM参数了。

比如，要想查找您问题中对应的JVM参数，步骤如下：

一、首先，使用java -XX:+PrintFlagsInitial |grep 关键词，获得关键词相关的JVM参数。如果是Windows，把grep换成findstr即可。

➜   java -XX:+PrintFlagsInitial |grep Tier
    uintx IncreaseFirstTierCompileThresholdAt       = 50                                  {product}
     bool PrintTieredEvents                         = false                               {product}
     intx Tier0BackedgeNotifyFreqLog                = 10                                  {product}
     intx Tier0InvokeNotifyFreqLog                  = 7                                   {product}
     intx Tier0ProfilingStartPercentage             = 200                                 {product}
     intx Tier23InlineeNotifyFreqLog                = 20                                  {product}
     intx Tier2BackEdgeThreshold                    = 0                                   {product}
     intx Tier2BackedgeNotifyFreqLog                = 14                                  {product}
     intx Tier2CompileThreshold                     = 0                                   {product}
     intx Tier2InvokeNotifyFreqLog                  = 11                                  {product}
     intx Tier3BackEdgeThreshold                    = 60000                               {product}
     intx Tier3BackedgeNotifyFreqLog                = 13                                  {product}
     intx Tier3CompileThreshold                     = 2000                                {product}
     intx Tier3DelayOff                             = 2                                   {product}
     intx Tier3DelayOn                              = 5                                   {product}
     intx Tier3InvocationThreshold                  = 200                                 {product}
     intx Tier3InvokeNotifyFreqLog                  = 10                                  {product}
     intx Tier3LoadFeedback                         = 5                                   {product}
     intx Tier3MinInvocationThreshold               = 100                                 {product}
     intx Tier4BackEdgeThreshold                    = 40000                               {product}
     intx Tier4CompileThreshold                     = 15000                               {product}
     intx Tier4InvocationThreshold                  = 5000                                {product}
     intx Tier4LoadFeedback                         = 3                                   {product}
     intx Tier4MinInvocationThreshold               = 600                                 {product}
     bool TieredCompilation                         = true                                {pd product}
     intx TieredCompileTaskTimeout                  = 50                                  {product}
     intx TieredRateUpdateMaxTime                   = 25                                  {product}
     intx TieredRateUpdateMinTime                   = 1                                   {product}
     intx TieredStopAtLevel                         = 4                                   {product}

二、对照 https://chriswhocodes.com （这个链接，在课程中有多次出现），输入参数，查询这些参数的含义。之后就知道答案啦。

PS. 多说一句，生产环境不建议随意调整这些参数，保持默认即可。

0

h91

h 感谢老师又传授了一招，瞬间解开了白天的疑惑，赞

h020-07-13

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