今天在SUN的jdk上测试了Thread栈占用内存的情况，帮助进一步了解JVM的内存模型。配置如下：
WIN7+4G
SUN JDK：
D:\maven\smart\smart>java -version
java version "1.6.0_21"
Java(TM) SE Runtime Environment (build 1.6.0_21-b06)
Java HotSpot(TM) Client VM (build 17.0-b16, mixed mode, sharing)
初始内存情况如下：
测试类代码如下：
package org.smart.threadtest;
public class ThreadStackTest extends Thread {
public ThreadStackTest(long num) {
super("[ThreadStackTest] Thread:" + num);
};
public void run() {
String threadName = Thread.currentThread().getName();
// System.out.println(threadName + " start.");
try {
Thread.sleep(10000);
} catch (Exception e) {
System.out.println("Exception from " + threadName + ".run");
}
}
public static void main(String[] args) {
ThreadStackTest t2 = null;
for (int i = 0; i < 10000; i++) {
System.out.println("Thread " + i + " start...");
t2 = new ThreadStackTest(i);
t2.start();
}
}
}
测试配置为：每个线程分配10240k就是10M的Stack，heap分配1024M，命令行如下：
D:\Java\jdk1.6.0_20\bin\java -Djava.compiler=NONE -verbose:gc -XX:+HeapDumpOnOutOfMemoryError
-XX:HeapDumpPath=d:/temp/java.phd -Xms1024m -Xmx1024m -XX:+PrintGCDetails
-XX:+PrintHeapAtGC -XX:ThreadStackSize=10240 -cp D:\maven\smart\smart\target\test-classes\
org.smart.threadtest.ThreadStackTest
输出结果：
Thread 72 start...
Thread 73 start...
Thread 74 start...
Thread 75 start...
Thread 76 start...
Exception in thread "main" java.lang.OutOfMemoryError: unable to create new native thread
at java.lang.Thread.start0(Native Method)
at java.lang.Thread.start(Thread.java:597)
at org.smart.threadtest.ThreadStackTest.main(ThreadStackTest.java:22)
Heap
def new generation total 314560K, used 14417K [0x03b50000, 0x190a0000, 0x190a0000)
eden space 279616K, 5% used [0x03b50000, 0x0493ba48, 0x14c60000)
from space 34944K, 0% used [0x16e80000, 0x16ea8d18, 0x190a0000)
to space 34944K, 0% used [0x14c60000, 0x14c60000, 0x16e80000)
tenured generation total 699072K, used 0K [0x190a0000, 0x43b50000, 0x43b50000)
the space 699072K, 0% used [0x190a0000, 0x190a0000, 0x190a0200, 0x43b50000)
compacting perm gen total 12288K, used 2088K [0x43b50000, 0x44750000, 0x47b50000)
the space 12288K, 16% used [0x43b50000, 0x43d5a110, 0x43d5a200, 0x44750000)
No shared spaces configured.
从输出可以看出，启动了76个线程之后，内存溢出，有两个比较奇怪的地方：
1、没有产生heapdump文件（注：如果是heap内存满可以产生，测试过，配置没有错）
2、在WIN7资源监视器中显示内存基本没有波动，也就是说这些内存只是被jvm标记，没有实际使用，包括heap–我猜
76×10M + 1024M = 1784M 大概为 1800M左右，和操作系统空闲差200M
修改测试配置，将heap大小调整到124M，命令如下：
D:\Java\jdk1.6.0_20\bin\java -Djava.compiler=NONE -verbose:gc -XX:+HeapDumpOnOutOfMemoryError
-XX:HeapDumpPath=d:/temp/java.phd -Xms124m -Xmx124m -XX:+PrintGCDetails
-XX:+PrintHeapAtGC -XX:ThreadStackSize=10240 -cp D:\maven\smart\smart\target\test-classes\
org.smart.threadtest.ThreadStackTest输出结果：
Thread 161 start...
Thread 162 start...
Thread 163 start...
Thread 164 start...
Thread 165 start...
Thread 166 start...
Exception in thread "main" java.lang.OutOfMemoryError: unable to create new native thread
at java.lang.Thread.start0(Native Method)
at java.lang.Thread.start(Thread.java:597)
at org.smart.threadtest.ThreadStackTest.main(ThreadStackTest.java:23)
Heap
def new generation total 38080K, used 23783K [0x2bee0000, 0x2e830000, 0x2e830000)
eden space 33856K, 69% used [0x2bee0000, 0x2d5ef4b8, 0x2dff0000)
from space 4224K, 4% used [0x2e410000, 0x2e43a860, 0x2e830000)
to space 4224K, 0% used [0x2dff0000, 0x2dff0000, 0x2e410000)
tenured generation total 84672K, used 0K [0x2e830000, 0x33ae0000, 0x33ae0000)
the space 84672K, 0% used [0x2e830000, 0x2e830000, 0x2e830200, 0x33ae0000)
compacting perm gen total 12288K, used 369K [0x33ae0000, 0x346e0000, 0x37ae0000)
the space 12288K, 3% used [0x33ae0000, 0x33b3c710, 0x33b3c800, 0x346e0000)
ro space 10240K, 54% used [0x37ae0000, 0x3805b760, 0x3805b800, 0x384e0000)
rw space 12288K, 55% used [0x384e0000, 0x38b7f798, 0x38b7f800, 0x390e0000)
结果显示启动了166个线程。
166×10M + 124M = 1784M 大概为1800M，结果和上面的对比一下，可以知道TreadStack确实占用的是操作系统内存，和heapsize本身无关。
IBM JDK:
java version "1.6.0"
Java(TM) SE Runtime Environment (build pwi3260sr8fp1ifix-20100924_01(SR8 FP1+IZ81201+IZ80998+IZ83034+IZ83273))
IBM J9 VM (build 2.4, JRE 1.6.0 IBM J9 2.4 Windows 7 x86-32 jvmwi3260sr8ifx-20100923_65174 (JIT enabled, AOT enabled)
J9VM - 20100923_065174
JIT - r9_20100401_15339ifx6
GC - 20100308_AA)
JCL - 20100728_01
测试类还是沿用上面测试SUN JDK的类：ThreadStackTest
设置环境变量：
IBM_HEAPDUMP_OUTOFMEMORY=TRUE
IBM_HEAPDUMPDIR=<directory>
IBM_JAVACOREDIR=<directory>
IBM_JAVADUMP_OUTOFMEMORY=TRUE
测试配置也相同：每个线程分配10240k就是10M的Stack，heap分配1024M，命令行如下：
D:\Java\ibm_jdk16.0\bin\java -Djava.compiler=NONE -verbose:gc,sizes -Xms1024m -Xmx1024m -Xss10240K -Xiss10240K
-cp D:\maven\smart\smart\target\test-classes\ org.smart.threadtest.ThreadStackTest
输出如下：
<?xml version="1.0" ?>
<verbosegc version="20100308_AA">
-Xmca32K RAM 类分段增量
-Xmco128K ROM 类分段增量
-Xmns0K 初始新空间大小
-Xmnx0K 最大新空间大小
-Xms1G 初始内存大小
-Xmos1G 初始旧空间大小
-Xmox1G 最大旧空间大小
-Xmx1G 最大内存
-Xmr16K 已记住的集合大小
-Xmso256K 操作系统线程堆栈大小
-Xiss10M Java 线程堆栈初始大小
-Xssi16K Java 线程堆栈增量
-Xss10M Java 线程堆栈最大大小
<initialized>
<attribute name="gcPolicy" value="-Xgcpolicy:optthruput" />
<attribute name="maxHeapSize" value="0x40000000" />
<attribute name="initialHeapSize" value="0x40000000" />
<attribute name="compressedRefs" value="false" />
<attribute name="pageSize" value="0x1000" />
<attribute name="requestedPageSize" value="0x1000" />
</initialized>
Thread 0 start...
Thread 1 start...
Thread 2 start...
......
......
Thread 81 start...
Thread 82 start...
<sys id="1" timestamp="Jan 26 14:35:08 2011" intervalms="0.000">
<time exclusiveaccessms="0.050" meanexclusiveaccessms="0.050" threads="0" lastthreadtid="0x41F92300" />
<refs soft="6" weak="4" phantom="0" dynamicSoftReferenceThreshold="32" maxSoftReferenceThreshold="32" />
<tenured freebytes="1072352000" totalbytes="1073741824" percent="99" >
<soa freebytes="1018665216" totalbytes="1020055040" percent="99" />
<loa freebytes="53686784" totalbytes="53686784" percent="100" />
</tenured>
<gc type="global" id="1" totalid="1" intervalms="0.000">
<classunloading classloaders="0" classes="0" timevmquiescems="0.000" timetakenms="0.087" />
<finalization objectsqueued="2" />
<timesms mark="13.684" sweep="4.105" compact="0.000" total="17.950" />
<tenured freebytes="1072855776" totalbytes="1073741824" percent="99" >
<soa freebytes="1019168992" totalbytes="1020055040" percent="99" />
<loa freebytes="53686784" totalbytes="53686784" percent="100" />
</tenured>
</gc>
<tenured freebytes="1072855776" totalbytes="1073741824" percent="99" >
<soa freebytes="1019168992" totalbytes="1020055040" percent="99" />
<loa freebytes="53686784" totalbytes="53686784" percent="100" />
</tenured>
<refs soft="1" weak="4" phantom="0" dynamicSoftReferenceThreshold="31" maxSoftReferenceThreshold="32" />
<time totalms="18.043" />
</sys>
JVMDUMP006I 正在处理转储事件“systhrow”，详细信息“java/lang/OutOfMemoryError”- 请稍候。
JVMDUMP032I JVM 使用“D:\IBM SOFT\IBM JVM\jca401\Snap.20110126.143508.15788.0001.trc”来请求 Snap 转储以响应事件
JVMDUMP010I Snap 转储已写入 D:\IBM SOFT\IBM JVM\jca401\Snap.20110126.143508.15788.0001.trc
JVMDUMP032I JVM 使用“d:\temp\heapdump.20110126.143508.15788.0002.phd”来请求 Heap 转储以响应事件
JVMDUMP010I Heap 转储已写入 d:\temp\heapdump.20110126.143508.15788.0002.phd
JVMDUMP032I JVM 使用“d:\temp\javacore.20110126.143508.15788.0003.txt”来请求 Java 转储以响应事件
JVMDUMP010I Java 转储已写入 d:\temp\javacore.20110126.143508.15788.0003.txt
JVMDUMP013I 已处理转储事件“systhrow”，详细信息：“java/lang/OutOfMemoryError”。
Exception in thread "main" java.lang.OutOfMemoryError: 未能分配 JNIEnv
at java.lang.Thread.startImpl(Native Method)
at java.lang.Thread.start(Thread.java:887)
at org.smart.threadtest.ThreadStackTest.main(ThreadStackTest.java:23)
82×10M + 1024M = 1844M，IBM JDK能够产生heapdump和core文件，这点比SUN JDK强，core文件内容如下：
同样将heapsize调整为124M测试，命令如下：
D:\Java\ibm_jdk16.0\bin\java -Djava.compiler=NONE -verbose:gc,sizes -Xms124m -Xmx124m -Xss10240K -Xiss10240K
-cp D:\maven\smart\smart\target\test-classes\ org.smart.threadtest.ThreadStackTest
输出如下：
<?xml version="1.0" ?>
<verbosegc version="20100308_AA">
-Xmca32K RAM 类分段增量
-Xmco128K ROM 类分段增量
-Xmns0K 初始新空间大小
-Xmnx0K 最大新空间大小
-Xms124M 初始内存大小
-Xmos124M 初始旧空间大小
-Xmox124M 最大旧空间大小
-Xmx124M 最大内存
-Xmr16K 已记住的集合大小
-Xmso256K 操作系统线程堆栈大小
-Xiss10M Java 线程堆栈初始大小
-Xssi16K Java 线程堆栈增量
-Xss10M Java 线程堆栈最大大小
<initialized>
<attribute name="gcPolicy" value="-Xgcpolicy:optthruput" />
<attribute name="maxHeapSize" value="0x7c00000" />
<attribute name="initialHeapSize" value="0x7c00000" />
<attribute name="compressedRefs" value="false" />
<attribute name="pageSize" value="0x1000" />
<attribute name="requestedPageSize" value="0x1000" />
</initialized>
Thread 0 start...
Thread 1 start...
......
......
Thread 169 start...
Thread 170 start...
<sys id="1" timestamp="Jan 26 14:42:31 2011" intervalms="0.000">
<time exclusiveaccessms="0.079" meanexclusiveaccessms="0.079" threads="0" lastthreadtid="0x0030EC00" />
<refs soft="6" weak="4" phantom="0" dynamicSoftReferenceThreshold="32" maxSoftReferenceThreshold="32" />
<tenured freebytes="128516864" totalbytes="130023424" percent="98" >
<soa freebytes="122016000" totalbytes="123522560" percent="98" />
<loa freebytes="6500864" totalbytes="6500864" percent="100" />
</tenured>
<gc type="global" id="1" totalid="1" intervalms="0.000">
<classunloading classloaders="0" classes="0" timevmquiescems="0.000" timetakenms="0.061" />
<finalization objectsqueued="2" />
<timesms mark="2.994" sweep="0.623" compact="0.000" total="3.768" />
<tenured freebytes="129057424" totalbytes="130023424" percent="99" >
<soa freebytes="122556560" totalbytes="123522560" percent="99" />
<loa freebytes="6500864" totalbytes="6500864" percent="100" />
</tenured>
</gc>
<tenured freebytes="129057424" totalbytes="130023424" percent="99" >
<soa freebytes="122556560" totalbytes="123522560" percent="99" />
<loa freebytes="6500864" totalbytes="6500864" percent="100" />
</tenured>
<refs soft="1" weak="4" phantom="0" dynamicSoftReferenceThreshold="31" maxSoftReferenceThreshold="32" />
<time totalms="3.899" />
</sys>
JVMDUMP006I 正在处理转储事件“systhrow”，详细信息“java/lang/OutOfMemoryError”- 请稍候。
JVMDUMP032I JVM 使用“D:\IBM SOFT\IBM JVM\jca401\Snap.20110126.144231.10464.0001.trc”来请求 Snap 转储以响应事件
JVMDUMP010I Snap 转储已写入 D:\IBM SOFT\IBM JVM\jca401\Snap.20110126.144231.10464.0001.trc
JVMDUMP032I JVM 使用“d:\temp\heapdump.20110126.144231.10464.0002.phd”来请求 Heap 转储以响应事件
JVMDUMP010I Heap 转储已写入 d:\temp\heapdump.20110126.144231.10464.0002.phd
JVMDUMP032I JVM 使用“d:\temp\javacore.20110126.144231.10464.0003.txt”来请求 Java 转储以响应事件
JVMDUMP010I Java 转储已写入 d:\temp\javacore.20110126.144231.10464.0003.txt
JVMDUMP013I 已处理转储事件“systhrow”，详细信息：“java/lang/OutOfMemoryError”。
Exception in thread "main" java.lang.OutOfMemoryError: 未能分配 JNIEnv
at java.lang.Thread.startImpl(Native Method)
at java.lang.Thread.start(Thread.java:887)
at org.smart.threadtest.ThreadStackTest.main(ThreadStackTest.java:23)
</verbosegc>
170×10M + 124M = 1824M ，与上面内存数量基本一致。
IBM JDK表现与SUN的JDK基本一致，都是占用操作系统内存。
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