blocks|key|2890894|text|ReservedCodeCacheSize+(和InitialCodeCacheSize)是Java的编译器的一个选项。基本上，它为编译器的代码缓存设置最大大小。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|2890895|缓存可能已满，这会产生如下警告：|2890896|Java+HotSpot(TM)+64-Bit+Server+VM+warning:+CodeCache+is+full.+Compiler+has+been+disabled.
Java+HotSpot(TM)+64-Bit+Server+VM+warning:+Try+increasing+the+code+cache+size+using+-XX:ReservedCodeCacheSize=
Code+Cache++[0x000000010958f000,+0x000000010c52f000,+0x000000010c58f000)
+total_blobs=15406+nmethods=14989+adapters=362+free_code_cache=835Kb+largest_free_block=449792|code-block|syntax|javascript|2890897|如果紧随其后的是Java+HotSpot(TM)+Client+VM+warning:+Exception+java.lang.OutOfMemoryError+occurred+dispatching+signal+SIGINT+to+handler-+the+VM+may+need+to+be+forcibly+terminated，情况就更糟了。|2890898|什么时候设置这个选项？|2890899|当热点编译器发生故障时，|2890900|，|ordered-list-item|2890901|，以减少JVM所需的内存(从而冒JIT编译器故障的风险)|2890902|2890903|通常您不会更改此值。我认为默认值是相当好的平衡，因为这个问题只发生在非常罕见的场合(在我的经验中)。|2890904|entityMap^0|0|L|O|K|0|0|0|8|4H|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|12|8|@$9|13|A|14|B|C]|$9|15|A|16|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|17|8|@]|D|@]|E|$]]|$1|H|3|I|5|J|7|18|8|@]|D|@]|E|$K|L]]|$1|M|3|N|5|6|7|19|8|@$9|1A|A|1B|B|C]]|D|@]|E|$]]|$1|O|3|P|5|6|7|1C|8|@]|D|@]|E|$]]|$1|Q|3|R|5|6|7|1D|8|@]|D|@]|E|$]]|$1|S|3|T|5|U|7|1E|8|@]|D|@]|E|$]]|$1|V|3|W|5|U|7|1F|8|@]|D|@]|E|$]]|$1|X|3|-4|5|6|7|1G|8|@]|D|@]|E|$]]|$1|Y|3|Z|5|6|7|1H|8|@]|D|@]|E|$]]|$1|10|3|-4|5|6|7|1I|8|@]|D|@]|E|$]]]|11|$]]

<code>ReservedCodeCacheSize</code> (and <code>InitialCodeCacheSize</code>) is an option for the (just-in-time) compiler of the Java Hotspot VM. Basically it sets the maximum size for the compiler's code cache.

The cache can become full, which results in warnings like the following:

<pre><code>Java HotSpot(TM) 64-Bit Server VM warning: CodeCache is full. Compiler has been disabled.
Java HotSpot(TM) 64-Bit Server VM warning: Try increasing the code cache size using -XX:ReservedCodeCacheSize=
Code Cache [0x000000010958f000, 0x000000010c52f000, 0x000000010c58f000)
 total_blobs=15406 nmethods=14989 adapters=362 free_code_cache=835Kb largest_free_block=449792
</code></pre>

It's much worse when followed by <code>Java HotSpot(TM) Client VM warning: Exception java.lang.OutOfMemoryError occurred dispatching signal SIGINT to handler- the VM may need to be forcibly terminated</code>.

When to set this option?

<ol>
<li>when having Hotspot compiler failures</li>
<li>to reduce memory needed by the JVM (and hence risking JIT compiler failures)</li>
</ol>

Normally you'd not change this value. I think the default values are quite good balanced because this problems occur on very rare occasions only (in my experince).

blocks|key|2890945|text|@jeha回答了我从这个问题中想知道的一切，除了设置参数到什么值之外。由于我没有编写我正在部署的代码，所以它的内存占用空间没有多少可见性。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2890946|但是，您可以使用j控制台将其附加到正在运行的java进程，然后使用“Memory”选项卡查找Cache大小。为了完整起见，步骤是(Linux环境，虽然我确信其他环境是相似的)：|2890947|moments)|2890948|Navigate+|unordered-list-item|2890949|在您的机器|ordered-list-item|2890950|上找到正确的进程ID并将j控制台附加到它(这将从“图表：”下拉列表中的“内存”选项卡|2890951|中获取几个jconsole，再次选择“内存池”“代码缓存”|2890952|，这可能需要一些时间才能刷新屏幕，然后您将看到如下内容：|2890953|G+211|offset|length|style|CODE|2890954|2890955|📷|atomic|2890956|如您所见，我的代码缓存使用的是大约49+MB。此时，文档(和@jeha)说的缺省值仍然是48+MB。当然，这对我来说是个很大的动力，可以增加我的背景！|2890957|本。|2890958|2890959|在默认情况下，1024+MB可能做得太过了，但默认情况下48+MB似乎不足.|2890960|entityMap|0|IMAGE|mutability|IMMUTABLE|imageUrl|https://developer.qcloudimg.com/http-save/yehe-900000/849481179005303e9466371014ef4693.jpg|imageAlt^0|0|0|0|0|0|0|0|0|0|5|0|0|0|1|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|1H|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|1I|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|1J|8|@]|9|@]|A|$]]|$1|F|3|G|5|H|7|1K|8|@]|9|@]|A|$]]|$1|I|3|J|5|K|7|1L|8|@]|9|@]|A|$]]|$1|L|3|M|5|K|7|1M|8|@]|9|@]|A|$]]|$1|N|3|O|5|K|7|1N|8|@]|9|@]|A|$]]|$1|P|3|Q|5|K|7|1O|8|@]|9|@]|A|$]]|$1|R|3|S|5|6|7|1P|8|@$T|1Q|U|1R|V|W]]|9|@]|A|$]]|$1|X|3|-4|5|6|7|1S|8|@]|9|@]|A|$]]|$1|Y|3|Z|5|10|7|1T|8|@]|9|@$T|1U|U|1V|1|1W]]|A|$]]|$1|11|3|12|5|6|7|1X|8|@]|9|@]|A|$]]|$1|13|3|14|5|6|7|1Y|8|@]|9|@]|A|$]]|$1|15|3|-4|5|6|7|1Z|8|@]|9|@]|A|$]]|$1|16|3|17|5|6|7|20|8|@]|9|@]|A|$]]|$1|18|3|-4|5|6|7|21|8|@]|9|@]|A|$]]]|19|$1A|$5|1B|1C|1D|A|$1E|1F|1G|-4]]]]

@jeha answers everything I wanted to know from this question, apart from what value to set the parameters to. As I didn't write the code I was deploying I didn't have much visibility into the memory footprint it had.

However, you can use jconsole to attach to your running java process, and then use the 'Memory' tab to find out the Code Cache size. For completeness, the steps are (Linux VM environment, though I'm sure other environments are similar):

<ol>
<li>Fire up jconsole on your machine</li>
<li>Find the right process ID and attach jconsole to it (this will take a few moments)</li>
<li>Navigate to the 'Memory' tab</li>
<li>From the 'Chart:' drop-down list, select 'Memory Pool "Code Cache"'</li>
<li>Again, this may take a few moments for the screen to refresh, and then you should see something like:
<img src="https://i.stack.imgur.com/gfxsu.jpg" alt="jconsole code cache image">

As you can see, my code cache is using approx 49 MB. At this point I still had the default which the documentation (and @jeha) says is 48 MB. Certainly a great motivation for me to increase the setting!

Ben.

<hr>

1024 MB by default probably was overdoing it, but 48 MB by default seems to be underdoing it...</li>
</ol>

blocks|key|2872728|text|从真正的工程团队获得良好的学习经验，以及他们在迁移到jdk+8时所面临的挑战。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2872729|http://engineering.indeedblog.com/blog/2016/09/job-search-web-app-java-8-migration/|offset|length|2872730|结论:+Jdk+8需要更多的代码缓存han+7。|2872731|JRE+8的默认代码缓存大小约为250+is，比JRE+7的48+is默认值大5倍。我们的经验是，JRE+8需要额外的代码缓存。到目前为止，我们已经将大约10种服务切换到了JRE+8，它们使用的编码比以前多了大约四倍。|2872732|entityMap|0|LINK|mutability|MUTABLE|url^0|0|0|2B|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|R|8|@]|9|@$D|S|E|T|1|U]]|A|$]]|$1|F|3|G|5|6|7|V|8|@]|9|@]|A|$]]|$1|H|3|I|5|6|7|W|8|@]|9|@]|A|$]]|$1|J|3|-4|5|6|7|X|8|@]|9|@]|A|$]]]|K|$L|$5|M|N|O|A|$P|C]]]]

A good learning experience from Indeed engineering team and challenges they faced when migrating to jdk 8.

<a href="http://engineering.indeedblog.com/blog/2016/09/job-search-web-app-java-8-migration/" rel="nofollow">http://engineering.indeedblog.com/blog/2016/09/job-search-web-app-java-8-migration/</a>

Conclusion : Jdk 8 needs more code cache han JDK 7

The default codecache size for JRE 8 is about 250MB, about five times larger than the 48MB default for JRE 7. Our experience is that JRE 8 needs that extra codecache. We have switched about ten services to JRE 8 so far, and all of them use about four times more codecache than before.

blocks|key|2891003|text|来自https://blogs.oracle.com/poonam/entry/why_do_i_get_message|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|2891004|2891005|以下是jdk7u4%2B中关于CodeCache刷新的两个已知问题：|blockquote|2891006|2891007|2891008|2891009|编译器即使在紧急刷新后占用的CodeCache减少到几乎一半之后也不会重新启动。|ordered-list-item|2891010|紧急刷新可能会导致编译器线程占用大量的CPU，从而导致整体性能下降。|2891011|2891012|这个性能问题，以及编译器不能再次重新启用的问题，已经在JDK8中解决了。为了在JDK7u4%2B中解决这些问题，我们可以使用ReservedCodeCacheSize选项增加代码缓存的大小，方法是将其设置为大于编译代码占用空间的值，这样CodeCache就不会满。另一种解决方案是使用-XX:-UseCodeCacheFlushing选项禁用CodeCache刷新。|2891013|上述问题已在JDK8及其更新中解决。|2891014|因此，对于在JDK+6(禁用代码刷新)和7上运行的系统来说，这些信息可能是值得一提的。|2891015|entityMap|0|LINK|mutability|MUTABLE|url|https://blogs.oracle.com/poonam/entry/why_do_i_get_message^0|2|1M|0|0|0|0|0|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|14|8|@]|9|@$A|15|B|16|1|17]]|C|$]]|$1|D|3|-4|5|6|7|18|8|@]|9|@]|C|$]]|$1|E|3|F|5|G|7|19|8|@]|9|@]|C|$]]|$1|H|3|-4|5|6|7|1A|8|@]|9|@]|C|$]]|$1|I|3|-4|5|6|7|1B|8|@]|9|@]|C|$]]|$1|J|3|-4|5|6|7|1C|8|@]|9|@]|C|$]]|$1|K|3|L|5|M|7|1D|8|@]|9|@]|C|$]]|$1|N|3|O|5|M|7|1E|8|@]|9|@]|C|$]]|$1|P|3|-4|5|6|7|1F|8|@]|9|@]|C|$]]|$1|Q|3|R|5|6|7|1G|8|@]|9|@]|C|$]]|$1|S|3|T|5|6|7|1H|8|@]|9|@]|C|$]]|$1|U|3|V|5|6|7|1I|8|@]|9|@]|C|$]]|$1|W|3|-4|5|6|7|1J|8|@]|9|@]|C|$]]]|X|$Y|$5|Z|10|11|C|$12|13]]]]

from <a href="https://blogs.oracle.com/poonam/entry/why_do_i_get_message" rel="nofollow">https://blogs.oracle.com/poonam/entry/why_do_i_get_message</a>:

<blockquote>
 The following are two known problems in jdk7u4+ with respect to the CodeCache flushing:
 
 <ol>
 <li>The compiler may not get restarted even after the CodeCache occupancy drops down to almost half after the emergency flushing.</li>
 <li>The emergency flushing may cause high CPU usage by the compiler threads leading to overall performance degradation. </li>
 </ol>
 
 This performance issue, and the problem of the compiler not getting re-enabled again has been addressed in JDK8. To workaround these in JDK7u4+, we can increase the code cache size using ReservedCodeCacheSize option by setting it to a value larger than the compiled-code footprint so that the CodeCache never becomes full. Another solution to this is to disable the CodeCache Flushing using -XX:-UseCodeCacheFlushing JVM option.
 
 The above mentioned issues have been fixed in JDK8 and its updates. 
</blockquote>

So that information might be worth mentioning for systems running on JDK 6 (having code flushing disabled) and 7.

Can someone please explain what the JVM option <code>ReservedCodeCacheSize</code> and <code>InitialCodeCacheSize</code> are? Specifically when/why would I want to change it? How do I decide what the right size is?

This is what the docs say:

<blockquote>
 -XX:ReservedCodeCacheSize=32m Reserved code cache size (in bytes) - maximum code cache size. [Solaris 64-bit, amd64, and -server x86: 2048m; in 1.5.0_06 and earlier, Solaris 64-bit and and64: 1024m.]
</blockquote>

What are ReservedCodeCacheSize and InitialCodeCacheSize?

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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请有人解释一下JVM选项ReservedCodeCacheSize和InitialCodeCacheSize是什么吗？具体来说，我什么时候/为什么要更改它？我该如何决定合适的尺码？医生们是这么说的： -XX:ReservedCodeCacheSize=32m保留的代码缓存大小(以字节为单位)-最大代码缓存大小。Sola...

问ReservedCodeCacheSize和InitialCodeCacheSize是什么？
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