[转帖]【JVM】常用虚拟机参数及实例

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正文

常用参数表

参数描述
-XX:+PrintGC启动java虚拟机后，只要遇到gc，就打印日志
-XX:+PrintGCDetailsgc发生时，打印更详细的日志
-XX:+PrintHeapAtGC每一次GC后，都打印堆信息
-XX:+PrintGCTimeStampsgc发生时，额外打印gc时间，该时间为虚拟机启动到现在的时间偏移量
-XX:+PrintGCApplicationStoppedTimegc时打印应用程序由于gc产生停顿的时间
-XX:+PrintReferenceGC跟踪系统的软引用，弱引用，虚引用和Finallize队列
-Xloggc指定gc日志的保存路径。
-XX:+TraceClassLoading跟踪类加载
-XX:+TraceClassUnloading跟踪类卸载
-XX:+PrintVMOptions程序运行时，打印虚拟机接收到的命令行显示参数
-XX:+PrintCommandLineFlags打印传递给虚拟机的显式和隐式参数
-XX:+PrintFlagsFinal打印所有系统参数的值
-XX:MaxHeapSize指定最大内存
-XX:SurvivorRatio指定新生代中eden区和from/to区的比例关系
-XX:NewRatio设置老年代/新生代的比例
-XX:+HeapDumpOnOutOfMemoryError内存溢出时，导出整个堆的信息，和下一个参数配合使用
-XX:HeapDumpPath导出的堆信息的保存路径，和上一个参数配合使用
-XX:OnOutOfMemoryError内存溢出发生错误时执行一个脚本文件
-XX:PermSize配置初始永久区的大小(JDK8中永久区已经被彻底移除，使用了新的元数据区存放类的元数据)
-XX:MaxPermSize配置最大永久区的大小(JDK8中永久区已经被彻底移除，使用了新的元数据区存放类的元数据)
-XX:MaxMetaspaceSize指定元数据区最大可用值
-Xss指定线程的栈大小
-Xms指定初始堆空间的大小，例如-Xms20m，默认是物理内存的1/64
-Xmx指定最大堆空间的大小，例如-Xmx100m，默认是物理内存的1/4
-Xmn指定新生代的大小，例如-Xmn1m
-XX:MaxDirectMemorySize指定最大可用直接内存值
-XX:+PrintCommandLineFlags将隐式或者显示传给虚拟机的参数输出
-XX:+TraceClassLoading监控加载的类信息（启动类加载器）
-server指定虚拟机在server模式下工作
-client指定虚拟机在client模式下工作
-XX:CMSInitiatingOccupancyFraction设定CMS在内存占用率达到指定值时开始GC(因为CMS会有浮动垃圾,所以一般都较早启动GC)，JDK5默认值68，而JDK6时默认值为92
-XX:+UseCMSInitiatingOccupancyOnly只用设定的回收阈值,若没有指定,JVM仅在第一次使用设定值,后续会自动调整
-XX:+CMSScavengeBeforeRemark在CMS GC前启动一次ygc，以减少old gen对ygc gen的引用，降低remark的时间(因为CMS GC耗时主要在remark阶段，该参数会使STW停顿时间变长

注：JDK8删除了永久区，用元数据区替代。

  • 将初始堆与最大堆大小设置相等，可以减少程序运行时的垃圾回收次数，从而提高性能。

  • 浅堆：一个对象结构所占用的内存大小
    对象大小按照8字节对齐、浅堆大小和对象的内容无关、只和对象的结构有关。

  • 深堆：一个对象被GC回收后，可以真实释放的内存大小
    只能通过对象访问到的所有对象的浅堆之和（支配树）

注：在命令行输入

  • java -verbose:class ：输出程序运行时类被加载信息
  • java –verbose:gc ：输出虚拟机发生内存回收时在输出设备显示信息
  • java -verbose:jni ：输出native方法调用的相关情况，一般用于诊断jni调用错误信息

例1：

配置参数：
-Xms5m
-Xmx20m
-XX:+PrintGCDetails
-XX:+UseSerialGC
-XX:+PrintCommandLineFlags


public class MemoryInfo {
    public static void main(String[] args) {
        //查看GC信息
        System.out.println("max memory : "+Runtime.getRuntime().maxMemory());
        System.out.println("free memory : "+Runtime.getRuntime().freeMemory());
        System.out.println("total memory : "+Runtime.getRuntime().totalMemory());

    <span class="token keyword">byte</span><span class="token punctuation">[</span><span class="token punctuation">]</span> b1 <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">byte</span><span class="token punctuation">[</span><span class="token number">1</span><span class="token operator">*</span><span class="token number">1024</span><span class="token operator">*</span><span class="token number">1024</span><span class="token punctuation">]</span><span class="token punctuation">;</span>

    System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token string">"分配1M  "</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token string">"max memory : "</span><span class="token operator">+</span>Runtime<span class="token punctuation">.</span><span class="token function">getRuntime</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token function">maxMemory</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token string">"free memory : "</span><span class="token operator">+</span>Runtime<span class="token punctuation">.</span><span class="token function">getRuntime</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token function">freeMemory</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token string">"total memory : "</span><span class="token operator">+</span>Runtime<span class="token punctuation">.</span><span class="token function">getRuntime</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token function">totalMemory</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>

    <span class="token keyword">byte</span><span class="token punctuation">[</span><span class="token punctuation">]</span> b2 <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">byte</span><span class="token punctuation">[</span><span class="token number">4</span><span class="token operator">*</span><span class="token number">1024</span><span class="token operator">*</span><span class="token number">1024</span><span class="token punctuation">]</span><span class="token punctuation">;</span>

    System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token string">"分配4M  "</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token string">"max memory : "</span><span class="token operator">+</span>Runtime<span class="token punctuation">.</span><span class="token function">getRuntime</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token function">maxMemory</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token string">"free memory : "</span><span class="token operator">+</span>Runtime<span class="token punctuation">.</span><span class="token function">getRuntime</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token function">freeMemory</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token string">"total memory : "</span><span class="token operator">+</span>Runtime<span class="token punctuation">.</span><span class="token function">getRuntime</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token function">totalMemory</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>

    <span class="token comment">//GC日志第三个十六进制数减去第一个十六进制数</span>
    <span class="token keyword">int</span> a <span class="token operator">=</span> <span class="token number">0x00000000fec00000</span><span class="token punctuation">;</span>
    <span class="token keyword">int</span> b <span class="token operator">=</span> <span class="token number">0x00000000ff2a0000</span><span class="token punctuation">;</span>
    System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token string">"结果为："</span><span class="token operator">+</span><span class="token punctuation">(</span>b<span class="token operator">-</span>a<span class="token punctuation">)</span><span class="token operator">/</span><span class="token number">1024</span><span class="token punctuation">)</span><span class="token punctuation">;</span>

<span class="token punctuation">}</span>



}

    输出结果（加注释）：

    //PrintCommandLineFlags命令打印的内容
-XX:InitialHeapSize=5242880 -XX:MaxHeapSize=20971520 -XX:+PrintCommandLineFlags -XX:+PrintGCDetails -XX:+UseCompressedClassPointers -XX:+UseCompressedOops -XX:-UseLargePagesIndividualAllocation -XX:+UseSerialGC 
//分配1M内存之后
[GC (Allocation Failure) [DefNew: 1664K->192K(1856K), 0.0014276 secs] 
//1664k是GC之前该内存已使用容量，GC后该内存使用容量192k，1856k是该内存区域总容量（1M）
1664K->699K(5952K), 0.0014631 secs] [Times: user=0.00 sys=0.00, real=0.00 secs] 
//方括号之外：1664k表示GC前Java堆已使用量，699k表示GC后Java堆已使用量，5952表示Java堆总容量。
//最大内存
max memory : 20316160
//空闲内存（值不确定）
free memory : 4426464
//初始分配的5M内存大小
total memory : 6094848
[GC (Allocation Failure) [DefNew: 1121K->120K(1856K), 0.0011164 secs] 1629K->818K(5952K), 0.0011364 secs] [Times: user=0.00 sys=0.00, real=0.00 secs] 
分配1M  
max memory : 20316160
//分配了1M之后，空闲内存变小了1M
free memory : 4178496
//总内存不变
total memory : 6094848
//GC收集之后，新生代收集前1173k，收集后为0，老年代1841k，Metaspace（之前的永久区）
[GC (Allocation Failure) [DefNew: 1173K->0K(1856K), 0.0010111 secs][Tenured: 1841K->1841K(4096K), 0.0021631 secs] 1871K->1841K(5952K), [Metaspace: 3513K->3513K(1056768K)], 0.0032147 secs] [Times: user=0.01 sys=0.00, real=0.00 secs] 
分配4M  
max memory : 20316160
//因为申请4M，空闲内存不够，向最大内存申请
free memory : 4246464
//申请4M之后，总内存增加4M
total memory : 10358784
结果为：7556
//-XX:+PrintGCDetails命令打印的内容
Heap
//新生代区，第三个十六进制数减第一个等于used的值，第二个十六进制值没有实际意义
 def new generation   total 1920K, used 66K [0x00000000fec00000, 0x00000000fee10000, 0x00000000ff2a0000)
  eden space 1728K,   3% used [0x00000000fec00000, 0x00000000fec10930, 0x00000000fedb0000)
  from space 192K,   0% used [0x00000000fedb0000, 0x00000000fedb0000, 0x00000000fede0000)
  to   space 192K,   0% used [0x00000000fede0000, 0x00000000fede0000, 0x00000000fee10000)
//老年代区
 tenured generation   total 8196K, used 5937K [0x00000000ff2a0000, 0x00000000ffaa1000, 0x0000000100000000)
   the space 8196K,  72% used [0x00000000ff2a0000, 0x00000000ff86c6c0, 0x00000000ff86c800, 0x00000000ffaa1000)
//元数据区，committed固定大小，reserved保留区大小
 Metaspace       used 3520K, capacity 4498K, committed 4864K, reserved 1056768K
  class space    used 388K, capacity 390K, committed 512K, reserved 1048576K

      例2

      配置参数

      -Xms20m
      -Xmx20m
      -Xmn1m
      -XX:SurvivorRatio=2
      -XX:+PrintGCDetails
      -XX:+UseSerialGC

      public class DefNew {

      <span class="token keyword">public</span> <span class="token keyword">static</span> <span class="token keyword">void</span> <span class="token function">main</span><span class="token punctuation">(</span>String<span class="token punctuation">[</span><span class="token punctuation">]</span> args<span class="token punctuation">)</span> <span class="token punctuation">{<!-- --></span>
    <span class="token keyword">byte</span><span class="token punctuation">[</span><span class="token punctuation">]</span> b <span class="token operator">=</span> null<span class="token punctuation">;</span>
    <span class="token comment">//连续向系统申请1M空间，一共10M</span>
    <span class="token keyword">for</span> <span class="token punctuation">(</span><span class="token keyword">int</span> i <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">;</span> i <span class="token operator">&lt;</span> <span class="token number">10</span><span class="token punctuation">;</span> i<span class="token operator">++</span><span class="token punctuation">)</span> <span class="token punctuation">{<!-- --></span>
        b <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">byte</span><span class="token punctuation">[</span><span class="token number">1</span><span class="token operator">*</span><span class="token number">1024</span><span class="token operator">*</span><span class="token number">1024</span><span class="token punctuation">]</span><span class="token punctuation">;</span>
    <span class="token punctuation">}</span>
<span class="token punctuation">}</span>

      

      }

        输出结果：

        [GC (Allocation Failure) [DefNew: 512K->256K(768K), 0.0011276 secs] 512K->432K(20224K), 0.0011600 secs] [Times: user=0.00 sys=0.00, real=0.00 secs] 
[GC (Allocation Failure) [DefNew: 767K->112K(768K), 0.0010947 secs] 943K->544K(20224K), 0.0011160 secs] [Times: user=0.00 sys=0.00, real=0.00 secs] 
[GC (Allocation Failure) [DefNew: 624K->255K(768K), 0.0007053 secs] 1056K->703K(20224K), 0.0007267 secs] [Times: user=0.00 sys=0.00, real=0.00 secs] 
[GC (Allocation Failure) [DefNew: 767K->56K(768K), 0.0007107 secs] 1215K->728K(20224K), 0.0007333 secs] [Times: user=0.02 sys=0.00, real=0.00 secs] 
Heap
 def new generation   total 768K, used 544K [0x00000000fec00000, 0x00000000fed00000, 0x00000000fed00000)
  eden space 512K,  95% used [0x00000000fec00000, 0x00000000fec79f30, 0x00000000fec80000)
  from space 256K,  21% used [0x00000000fec80000, 0x00000000fec8e128, 0x00000000fecc0000)
  to   space 256K,   0% used [0x00000000fecc0000, 0x00000000fecc0000, 0x00000000fed00000)
 tenured generation   total 19456K, used 10911K [0x00000000fed00000, 0x0000000100000000, 0x0000000100000000)
   the space 19456K,  56% used [0x00000000fed00000, 0x00000000ff7a7f90, 0x00000000ff7a8000, 0x0000000100000000)
 Metaspace       used 3517K, capacity 4498K, committed 4864K, reserved 1056768K
  class space    used 388K, capacity 390K, committed 512K, reserved 1048576K

          还有两种参数配置，如果有兴趣可以尝试配置，然后输出结果

          （1）

          -Xms20m -Xmx20m -Xmn1m -XX:SurvivorRatio=2 -XX:PrintGCDetails 
-XX:+UseSerialGC

            （2）

            -Xms20m -Xmx20m -XX:NewRatio=2 -XX:PrintGCDetails -XX:+UseSerialGC

              例3

              配置参数
              -Xms64m
              -Xmx64m
              -XX:+PrintGCDetails

              public class EnterEdenSurvivor {
    public static void main(String[] args) {
        //初始化的对象在eden区
        for (int i=0; i < 5; i++) {
            byte[] b = new byte[1*1024*1024];
        }
    }
}

                输出结果

                Heap
 PSYoungGen      total 18944K, used 8403K [0x00000000feb00000, 0x0000000100000000, 0x0000000100000000)
  eden space 16384K, 51% used [0x00000000feb00000,0x00000000ff334f80,0x00000000ffb00000)
  from space 2560K, 0% used [0x00000000ffd80000,0x00000000ffd80000,0x0000000100000000)
  to   space 2560K, 0% used [0x00000000ffb00000,0x00000000ffb00000,0x00000000ffd80000)
 ParOldGen       total 44032K, used 0K [0x00000000fc000000, 0x00000000feb00000, 0x00000000feb00000)
  object space 44032K, 0% used [0x00000000fc000000,0x00000000fc000000,0x00000000feb00000)
 Metaspace       used 3517K, capacity 4498K, committed 4864K, reserved 1056768K
  class space    used 388K, capacity 390K, committed 512K, reserved 1048576K

                  例4
                  配置参数
                  -Xmx1024m
                  -Xms1024m
                  -XX:+UseSerialGC
                  -XX:MaxTenuringThreshold=15
                  -XX:+PrintGCDetails

                      public static void maxTenure() {
        Map<Integer,byte[]> m = new HashMap<Integer,byte[]>();
        for (int i = 0; i < 5; i++) {
            byte[] b = new byte[1024*1024];
            m.put(i,b);
        }

                      <span class="token keyword">for</span> <span class="token punctuation">(</span><span class="token keyword">int</span> k <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">;</span> k <span class="token operator">&lt;</span> <span class="token number">20</span><span class="token punctuation">;</span> k<span class="token operator">++</span><span class="token punctuation">)</span> <span class="token punctuation">{<!-- --></span>
        <span class="token keyword">for</span> <span class="token punctuation">(</span><span class="token keyword">int</span> j <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">;</span> j <span class="token operator">&lt;</span> <span class="token number">300</span><span class="token punctuation">;</span> j<span class="token operator">++</span><span class="token punctuation">)</span> <span class="token punctuation">{<!-- --></span>
            <span class="token keyword">byte</span><span class="token punctuation">[</span><span class="token punctuation">]</span> b <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">byte</span><span class="token punctuation">[</span><span class="token number">1024</span><span class="token operator">*</span><span class="token number">1024</span><span class="token punctuation">]</span><span class="token punctuation">;</span>
        <span class="token punctuation">}</span>
    <span class="token punctuation">}</span>
<span class="token punctuation">}</span>

                    输出结果

                    [GC (Allocation Failure) [DefNew: 278925K->5937K(314560K), 0.0035484 secs] 278925K->5937K(1013632K), 0.0035893 secs] [Times: user=0.00 sys=0.00, real=0.00 secs] 
//中间省略类似的13行
[GC (Allocation Failure) [DefNew: 284897K->5903K(314560K), 0.0023524 secs] 284897K->5903K(1013632K), 0.0023898 secs] [Times: user=0.00 sys=0.00, real=0.00 secs] 
[GC (Allocation Failure) [DefNew: 284897K->0K(314560K), 0.0033498 secs] 284897K->5903K(1013632K), 0.0033751 secs] [Times: user=0.00 sys=0.00, real=0.00 secs] 
[GC (Allocation Failure) [DefNew: 278994K->0K(314560K), 0.0002507 secs] 284897K->5903K(1013632K), 0.0002911 secs] [Times: user=0.00 sys=0.00, real=0.00 secs] 
[GC (Allocation Failure) [DefNew: 278994K->0K(314560K), 0.0001911 secs] 284898K->5903K(1013632K), 0.0002124 secs] [Times: user=0.00 sys=0.00, real=0.00 secs] 
[GC (Allocation Failure) [DefNew: 278995K->0K(314560K), 0.0002929 secs] 284898K->5903K(1013632K), 0.0003164 secs] [Times: user=0.00 sys=0.00, real=0.00 secs] 
[GC (Allocation Failure) [DefNew: 278995K->0K(314560K), 0.0002338 secs] 284898K->5903K(1013632K), 0.0002560 secs] [Times: user=0.00 sys=0.00, real=0.00 secs] 
[GC (Allocation Failure) [DefNew: 278995K->0K(314560K), 0.0001902 secs] 284898K->5903K(1013632K), 0.0002102 secs] [Times: user=0.00 sys=0.00, real=0.00 secs] 
[GC (Allocation Failure) [DefNew: 278995K->0K(314560K), 0.0001920 secs] 284898K->5903K(1013632K), 0.0002120 secs] [Times: user=0.00 sys=0.00, real=0.00 secs] 
Heap
 def new generation   total 314560K, used 45992K [0x00000000c0000000, 0x00000000d5550000, 0x00000000d5550000)
  eden space 279616K,  16% used [0x00000000c0000000, 0x00000000c2cea0e8, 0x00000000d1110000)
  from space 34944K,   0% used [0x00000000d1110000, 0x00000000d1110000, 0x00000000d3330000)
  to   space 34944K,   0% used [0x00000000d3330000, 0x00000000d3330000, 0x00000000d5550000)
 tenured generation   total 699072K, used 5903K [0x00000000d5550000, 0x0000000100000000, 0x0000000100000000)
   the space 699072K,   0% used [0x00000000d5550000, 0x00000000d5b13c50, 0x00000000d5b13e00, 0x0000000100000000)
 Metaspace       used 3519K, capacity 4498K, committed 4864K, reserved 1056768K
  class space    used 388K, capacity 390K, committed 512K, reserved 1048576K

                      例5

                      配置参数
                      -Xss1m

                      public class StackOverFlow {

                      <span class="token comment">//栈调用深度</span>
<span class="token keyword">private</span> <span class="token keyword">static</span> <span class="token keyword">int</span> count<span class="token punctuation">;</span>

<span class="token keyword">public</span> <span class="token keyword">static</span> <span class="token keyword">void</span> <span class="token function">recursion</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{<!-- --></span>
    count<span class="token operator">++</span><span class="token punctuation">;</span>
    <span class="token function">recursion</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>

<span class="token keyword">public</span> <span class="token keyword">static</span> <span class="token keyword">void</span> <span class="token function">main</span><span class="token punctuation">(</span>String<span class="token punctuation">[</span><span class="token punctuation">]</span> args<span class="token punctuation">)</span> <span class="token punctuation">{<!-- --></span>
    <span class="token keyword">try</span> <span class="token punctuation">{<!-- --></span>
        <span class="token function">recursion</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token punctuation">}</span><span class="token keyword">catch</span><span class="token punctuation">(</span>Throwable e<span class="token punctuation">)</span><span class="token punctuation">{<!-- --></span>
        System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token string">"调用最大栈深度："</span><span class="token operator">+</span>count<span class="token punctuation">)</span><span class="token punctuation">;</span>
        e<span class="token punctuation">.</span><span class="token function">printStackTrace</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token punctuation">}</span>
<span class="token punctuation">}</span>

                      

                      }

                        输出结果

                        调用最大栈深度：23533
java.lang.StackOverflowError
	at jvm.StackOverFlow.recursion(StackOverFlow.java:19)
	at jvm.StackOverFlow.recursion(StackOverFlow.java:19)
	at jvm.StackOverFlow.recursion(StackOverFlow.java:19)
	//省略一样的许多行

                          推荐JVM参数设置

                          应用场景：对于长连接，push一类的海量服务端应用，16G内存8核心，推荐的JVM参数如下（仅供参考）：

                          JDK1.7JDK1.8
                          Xms12g-
                          Xmx12g-
                          Xss512k-
                          -XX:PermSize=384m无
                          -XX:MaxPermSize=384m无
                          -XX:NewSize=12g-
                          -XX:MaxNewSize=12g-
                          -XX:SurvivorRatio=18-
                          -XX:MaxDirectMemorySize=2g-
                          -XX:+UseParNewGC-
                          -XX:ParallelGCThreads=4-
                          -XX:MaxTenuringThreshold=15-
                          -XX:+CMSParallelRemarkEnabled-
                          -XX:+CMSScavengeBeforeRemark-
                          -XX:+UseConcMarkSweepGC-
                          -XX:+DisableExplicitGC-
                          -XX:+UseCMSInitiatingOccupancyOnly-
                          -XX:CMSInitiatingOccupancyFraction=70-
                          -XX:+ScavengeBeforeFullGC-
                          -XX:+UseCMSCompactAtFullCollection-
                          -XX:CMSFullGCsBeforeCompaction=9-
                          -XX:+CMSClassUnloadingEnabled-
                          -XX:CMSInitiatingPermOccupancyFraction=70-
                          -XX:+ExplicitGCInvokesConcurrent-
                          -XX:+PrintGCDetails-
                          -XX:+PrintGCDateStamps-
                          -XX:+PrintGCApplicationConcurrentTime-
                          -XX:+PrintHeapAtGC-
                          -Xloggc:/data/applogs/heap_trace.txt-
                          -XX:-HeapDumpOnOutOfMemoryError-
                          -XX:HeapDumpPath=/data/applogs/heapdump_oom.hprof-

                          本人才疏学浅，若有错，请指出
                          谢谢！

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