启动JVM时-XMS和-XMX参数是什么？

Question

启动JVM时-XMS和-XMX参数是什么？

请解释使用Xms和XmxJVM中的参数。它们的默认值是什么？

Answer 1

国旗Xmx指定Java虚拟机(JVM)的最大内存分配池，而Xms指定初始内存分配池。这意味着您的jvm将在Xms内存的数量，并且将能够最大限度地使用Xmx内存的数量。例如，像下面这样启动JVM将使用256 MB的内存启动它，并允许进程使用最多2048 MB的内存：java -Xms256m -Xmx2048m还可以指定不同大小的内存标志，例如千字节、兆字节等。-Xmx1024k-Xmx512m-Xmx8g这个Xms标志没有默认值，并且Xmx默认值通常为256 MB。这些标志的一个常见用途是当您遇到java.lang.OutOfMemoryError.在使用这些设置时，请记住这些设置是针对JVM的堆，而且JVM可以/将使用更多的内存，而不仅仅是分配给堆的大小。请注意，JVM使用的内存比堆更多。例如，Java方法、线程堆栈和本机句柄是在与堆分离的内存以及JVM内部数据结构中分配的。

Answer 2

运行命令java -X你会得到一张清单-X备选方案：C:\Users\Admin>java -X-Xmixed&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;mixed mode execution (default)-Xint&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;interpreted mode execution only-Xbootclasspath:<directories and zip/jar files separated by ;>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; set search path for bootstrap classes and resources-Xbootclasspath/a:<directories and zip/jar files separated by ;>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; append to end of bootstrap class path-Xbootclasspath/p:<directories and zip/jar files separated by ;>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; prepend in front of bootstrap class path-Xdiag&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; show additional diagnostic messages-Xnoclassgc&nbsp; &nbsp; &nbsp; &nbsp;disable class garbage collection-Xincgc&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;enable incremental garbage collection-Xloggc:<file>&nbsp; &nbsp; log GC status to a file with time stamps-Xbatch&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;disable background compilation-Xms<size>&nbsp; &nbsp; &nbsp; &nbsp; set initial Java heap size.........................-Xmx<size>&nbsp; &nbsp; &nbsp; &nbsp; set maximum Java heap size.........................-Xss<size>&nbsp; &nbsp; &nbsp; &nbsp; set java thread stack size-Xprof&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; output cpu profiling data-Xfuture&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; enable strictest checks, anticipating future default-Xrs&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; reduce use of OS signals by Java/VM (see documentation)-Xcheck:jni&nbsp; &nbsp; &nbsp; &nbsp;perform additional checks for JNI functions-Xshare:off&nbsp; &nbsp; &nbsp; &nbsp;do not attempt to use shared class data-Xshare:auto&nbsp; &nbsp; &nbsp; use shared class data if possible (default)-Xshare:on&nbsp; &nbsp; &nbsp; &nbsp; require using shared class data, otherwise fail.-XshowSettings&nbsp; &nbsp; show all settings and continue-XshowSettings:all&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;show all settings and continue-XshowSettings:vm&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; show all vm related settings and continue-XshowSettings:properties&nbsp; show all property settings and continue-XshowSettings:locale&nbsp; &nbsp; &nbsp; show all locale related settings and continue-X选项是非标准的，如有更改，恕不另行通知.我希望这能帮助你理解Xms, Xmx还有很多其他最重要的事情。*)

Answer 3

您可以在IDE中指定它。例如，对于Eclipsein运行配置&nbsp;→&nbsp;VM参数..你可以进去-Xmx800m -Xms500m