[转帖]【JVM】常用虚拟机参数及实例

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:+PrintGCDetails	gc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:+PrintGCTimeStamps	gc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:+PrintGCApplicationStoppedTime	gc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

JDK1.7	JDK1.8
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	-

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[转帖]【JVM】常用虚拟机参数及实例

例1：

推荐JVM参数设置

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