jvm启动参数不会消耗在-Xms中声明的内存
在运行java应用程序之前，我的linux可用内存是4942356kb。我的启动参数使用-Xmx2048m和-Xms2048m将最大堆内存和初始堆内存设置为2G。但我发现在启动应用程序后，我的linux系统可用内存正在逐步减少，而不是启动后消耗的2G内存。有人能告诉我原因和机制吗 还有一个问题，我的jvm启动参数是jvm启动参数不会消耗在-Xms中声明的内存,jvm,out-of-memory,jvm-hotspot,Jvm,Out Of Memory,Jvm Hotspot,在运行java应用程序之前，我的linux可用内存是4942356kb。我的启动参数使用-Xmx2048m和-Xms2048m将最大堆内存和初始堆内存设置为2G。但我发现在启动应用程序后，我的linux系统可用内存正在逐步减少，而不是启动后消耗的2G内存。有人能告诉我原因和机制吗 还有一个问题，我的jvm启动参数是-XX:+PrintGCDetails-Xss512k-Xmx4096m-Xms4096m-Xloggc:gc_01221859.log，启动前的可用内存是5G，1小时后，我发现这个应
-XX:+PrintGCDetails-Xss512k-Xmx4096m-Xms4096m-Xloggc:gc_01221859.logjcmd VM.native_memory summaryNative Memory Tracking:
Total: reserved=8688195KB, committed=8645103KB
- Java Heap (reserved=2181632KB, committed=2181632KB)
(mmap: reserved=2181632KB, committed=2181632KB)
- Class (reserved=5997KB, committed=5997KB)
(classes #8918)
(malloc=5997KB, #7418)
- Thread (reserved=5815888KB, committed=5815888KB)
(thread #11139)
(stack: reserved=5752332KB, committed=5752332KB)
(malloc=35936KB, #44562)
(arena=27620KB, #22266)
- Code (reserved=51385KB, committed=8293KB)
(malloc=1465KB, #2689)
(mmap: reserved=49920KB, committed=6828KB)
- GC (reserved=85657KB, committed=85657KB)
(malloc=5889KB, #155)
(mmap: reserved=79768KB, committed=79768KB)
- Compiler (reserved=294KB, committed=294KB)
(malloc=196KB, #400)
(arena=98KB, #2)
- Internal (reserved=52609KB, committed=52609KB)
(malloc=52609KB, #283728)
- Symbol (reserved=13406KB, committed=13406KB)
(malloc=10010KB, #98269)
(arena=3396KB, #1)
- Memory Tracking (reserved=301363KB, committed=301363KB)
(malloc=301363KB, #28396)
- Pooled Free Chunks (reserved=179933KB, committed=179933KB)
(malloc=179933KB)
- Unknown (reserved=32KB, committed=32KB)
(mmap: reserved=32KB, committed=32KB)
top - 18:47:02 up 397 days, 26 min, 1 user, load average: 3.68, 3.46, 2.58
Tasks: 164 total, 1 running, 163 sleeping, 0 stopped, 0 zombie
Cpu(s): 2.5%us, 0.6%sy, 0.0%ni, 96.7%id, 0.1%wa, 0.0%hi, 0.0%si, 0.1%st
Mem: 5990984k total, 5144764k used, 846220k free, 11564k buffers
Swap: 0k total, 0k used, 0k free, 132748k cached
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
11513 wuchang 20 0 12.1g 3.7g 15m S 188.8 64.9 41:46.42 java
1264 wuchang 20 0 17116 1240 900 R 1.8 0.0 0:00.02 top
1 root 20 0 19232 364 84 S 0.0 0.0 0:02.57 init
total used free shared buffers cached
Mem: 5990984 5786744 204240 0 12012 134092
-/+ buffers/cache: 5640640 350344
Swap: 0 0 0
public class CreateThread {
private static int threadNumber = 0;
public static void main(String[] args) {
while (true) {
new Thread(new Runnable() {
@Override
public void run() {
// TODO Auto-generated method stub
System.out.println("Thread " + threadNumber++);
while(true){
try {
Thread.sleep(20000);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
}).start();
}
}
}
java -Xss512k -jar CreateThread.jar > /home/wuchang/test
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:714)
at CreateThread.main(CreateThread.java:22)
[wuchang@hz10-45-88 ~]$ cat /proc/sys/kernel/threads-max
93335
[wuchang@hz10-45-88 ~]$ ulimit -u
46667
更新1: 每次我用不同的启动参数运行java应用程序时，包括三种情况：
case 1: -Xss512k -Xmx4096m -Xms4096m
case 2: -Xss512k -Xmx2048m -Xms2048m
case 3: -Xss256k -Xmx2048m -Xms2048m
case 1:
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
18136 wuchang 20 0 15.4g 4.3g 6456 S 99.3 75.0 36:16.22 java
case 2:
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
9689 wuchang 20 0 15.0g 4.2g 14m S 98.6 73.0 55:36.62 java
case 3:
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
8237 wuchang 20 0 10.1g 4.2g 9284 S 100.6 74.0 60:43.95 java
更新2: 我已经运行了@Ivan提供的代码：
public class CreateThread {
private static int threadNumber = 0;
public static int doRecursiveCall(int i) throws StackOverflowError {
return doRecursiveCall(++i);
}
public static void warmupNativeStack() {
int sideEffect;
try {
sideEffect = doRecursiveCall(0);
} catch (StackOverflowError ignored) {
return;
}
System.out.println("Never happend " + sideEffect);
}
public static void main(String[] args) {
while (true) {
new Thread(new Runnable() {
@Override
public void run() {
warmupNativeStack();
System.out.println("Thread " + threadNumber++);
while (true) {
try {
Thread.sleep(20000);
} catch (InterruptedException e) {
Thread.currentThread().interrupt();
}
}
}
}).start();
}
}
}
java -Xss512k -Xmx2048m -Xms2048m -jar CreateThread.jar
totally 8600 threads are created.before exit,the max VIRT is 8.7G and max RSS is 4.5G
java -Xss256k -Xmx2048m -Xms2048m -jar CreateThread.jar
totally 16780 threads are created.before exit,the max VIRT is 8.7G and max RSS is 4.6G
实验表明，在这种情况下，max-VIRT和RSS与jvm启动参数无关，它们保持不变。因此，根据UPDATE 1和UPDATE 2的实验结果，我猜，我的应用程序被操作系统杀死的原因可能是RSS内存已达到极限，默认情况下，JVM在应用程序执行期间增量地接触页面，而不是线程数或总VIRT，对吗。要更改此行为，请使用以下选项
-XX:+AlwaysPreTouchpmap-xpublic class CreateThread {
private static int threadNumber = 0;
public static int doRecursiveCall(int i) throws StackOverflowError {
return doRecursiveCall(++i);
}
public static void warmupNativeStack() {
int sideEffect;
try {
sideEffect = doRecursiveCall(0);
} catch (StackOverflowError ignored) {
return;
}
System.out.println("Never happend " + sideEffect);
}
public static void main(String[] args) {
while (true) {
new Thread(new Runnable() {
@Override
public void run() {
warmupNativeStack();
System.out.println("Thread " + threadNumber++);
while (true) {
try {
Thread.sleep(20000);
} catch (InterruptedException e) {
Thread.currentThread().interrupt();
}
}
}
}).start();
}
}
}
这取决于许多因素，JVM参数不起任何作用。例如，您必须知道应用程序中调用堆栈的最大深度-使用您和我的示例检查线程数 请提供JVM本机内存跟踪器的信息。您好，已经提供了jcmd OUTPOUT。我只是不明白为什么堆栈内存总量会大于系统可用内存。非常感谢。请不要频繁更改问题。这很难读。如果您有新问题-创建新问题，而不是更改此问题好的。非常感谢您的帮助。我已将您的代码输出更新为更新2。有什么建议吗？查看OOM killer日志，很难说清楚。谢谢。我使用top命令，这表明我的交换大小为零。然后，什么会使我的堆栈总内存大于系统总可用内存？请提供“空闲”和内部内存使用情况的输出
-XX:NativeMemoryTracking=summary