jps -l -m -v

31427 sun.tools.jps.Jps -l -m -v -Dapplication.home=/Library/Java/JavaVirtualMachines/jdk1.7.0_55.jdk/Contents/Home -Xms8m

jstat -<option> [-t] [-h<lines>] <vmid> [<interval> [<count>]] 

jstat -class pid:显示加载class的数量，及所占空间等信息。  

jstat -compiler pid:显示VM实时编译的数量等信息。

jstat -gc pid:可以显示gc的信息，查看gc的次数，及时间。其中最后五项，分别是young gc的次数，young gc的时间，full gc的次数，full gc的时间，gc的总时间。

jstat -gccapacity:可以显示，VM内存中三代（young,old,perm）对象的使用和占用大小，如：PGCMN显示的是最小perm的内存使用量，PGCMX显示的是perm的内存最大使用量，PGC是当前新生成的perm内存占用量，PC是但前perm内存占用量。其他的可以根据这个类推， OC是old内纯的占用量。

jstat -gcnew pid:new对象的信息。

jstat -gcnewcapacity pid:new对象的信息及其占用量。

jstat -gcold pid:old对象的信息。

jstat -gcoldcapacity pid:old对象的信息及其占用量。

jstat -gcpermcapacity pid: perm对象的信息及其占用量。

jstat -gcutil pid:统计gc信息统计。

jstat -printcompilation pid:当前VM执行的信息。

除了以上一个参数外，还可以同时加上 两个数字，如：jstat -printcompilation 3024 250 6是每250毫秒打印一次，一共打印6次。

S0  — Heap上的 Survivor space 0 区已使用空间的百分比  

S1 — Heap上的 Survivor space 1 区已使用空间的百分比

E — Heap上的 Eden space 区已使用空间的百分比

O — Heap上的 Old space 区已使用空间的百分比

P — Perm space 区已使用空间的百分比

YGC — 从应用程序启动到采样时发生 Young GC 的次数

YGCT– 从应用程序启动到采样时 Young GC 所用的时间(单位秒)

FGC — 从应用程序启动到采样时发生 Full GC 的次数

FGCT– 从应用程序启动到采样时 Full GC 所用的时间(单位秒)

GCT — 从应用程序启动到采样时用于垃圾回收的总时间(单位秒)

实例使用1：

[root@localhost bin]# jstat -gcutil 25444

S0 S1 E O P YGC YGCT FGC FGCT GCT

11.63 0.00 56.46 66.92 98.49 162 0.248 6 0.331 0.579

jinfo  <option>  <pid>

jinfo -flag MaxTenuringThreshold 31518

-XX:MaxTenuringThreshold=15

> jinfo -flag PrintGCDetails 31518

-XX:-PrintGCDetails

> jinfo -flag +PrintGCDetails 31518

> jinfo -flag PrintGCDetails 31518

-XX:+PrintGCDetails

> jmap -dump:format=b,file=heap.hprof 31531

Dumping heap to /Users/caojie/heap.hprof ...

Heap dump file created

> jhat heap.hprof 

Reading from heap.hprof...

Dump file created Tue Nov 11 06:02:05 CST 2014

Snapshot read, resolving...

Resolving 8781 objects...

Chasing references, expect 1 dots.

Eliminating duplicate references.

Snapshot resolved.

Started HTTP server on port 7000

Server is ready.

jstack -l <pid>

public class DeadLock extends Thread {

protected Object myDirect;

static ReentrantLock south = new ReentrantLock();

static ReentrantLock north = new ReentrantLock();

public DeadLock(Object obj) {

this.myDirect = obj;

if (myDirect == south) {

this.setName("south");

}

if (myDirect == north) {

this.setName("north");

}

}

@Override

public void run() {

if (myDirect == south) {

try {

north.lockInterruptibly();

try {

Thread.sleep(500);

} catch (Exception e) {

e.printStackTrace();

}

south.lockInterruptibly();

System.out.println("car to south has passed");

} catch (InterruptedException e1) {

System.out.println("car to south is killed");

} finally {

if (north.isHeldByCurrentThread())

north.unlock();

if (south.isHeldByCurrentThread())

south.unlock();

}

}

if (myDirect == north) {

try {

south.lockInterruptibly();

try {

Thread.sleep(500);

} catch (Exception e) {

e.printStackTrace();

}

north.lockInterruptibly();

System.out.println("car to north has passed");

} catch (InterruptedException e1) {

System.out.println("car to north is killed");

} finally {

if (north.isHeldByCurrentThread())

north.unlock();

if (south.isHeldByCurrentThread())

south.unlock();

}

}

}

public static void main(String[] args) throws InterruptedException {

DeadLock car2south = new DeadLock(south);

DeadLock car2north = new DeadLock(north);

car2south.start();

car2north.start();

Thread.sleep(1000);

}

}

2014-11-11 21:33:12

Full thread dump Java HotSpot(TM) 64-Bit Server VM (24.55-b03 mixed mode):

"Attach Listener" daemon prio=5 tid=0x00007f8d0c803000 nid=0x3307 waiting on condition [0x0000000000000000]

java.lang.Thread.State: RUNNABLE

Locked ownable synchronizers:

- None

"DestroyJavaVM" prio=5 tid=0x00007f8d0b80b000 nid=0x1903 waiting on condition [0x0000000000000000]

java.lang.Thread.State: RUNNABLE

Locked ownable synchronizers:

- None

"north" prio=5 tid=0x00007f8d0c075000 nid=0x5103 waiting on condition [0x0000000115b06000]

java.lang.Thread.State: WAITING (parking)

at sun.misc.Unsafe.park(Native Method)

- parking to wait for <0x00000007d55ab600> (a java.util.concurrent.locks.ReentrantLock$NonfairSync)

at java.util.concurrent.locks.LockSupport.park(LockSupport.java:186)

at java.util.concurrent.locks.AbstractQueuedSynchronizer.parkAndCheckInterrupt(AbstractQueuedSynchronizer.java:834)

at java.util.concurrent.locks.AbstractQueuedSynchronizer.doAcquireInterruptibly(AbstractQueuedSynchronizer.java:894)

at java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireInterruptibly(AbstractQueuedSynchronizer.java:1221)

at java.util.concurrent.locks.ReentrantLock.lockInterruptibly(ReentrantLock.java:340)

at DeadLock.run(DeadLock.java:48)

Locked ownable synchronizers:

- <0x00000007d55ab5d0> (a java.util.concurrent.locks.ReentrantLock$NonfairSync)

"south" prio=5 tid=0x00007f8d0c074800 nid=0x4f03 waiting on condition [0x0000000115a03000]

java.lang.Thread.State: WAITING (parking)

at sun.misc.Unsafe.park(Native Method)

- parking to wait for <0x00000007d55ab5d0> (a java.util.concurrent.locks.ReentrantLock$NonfairSync)

at java.util.concurrent.locks.LockSupport.park(LockSupport.java:186)

at java.util.concurrent.locks.AbstractQueuedSynchronizer.parkAndCheckInterrupt(AbstractQueuedSynchronizer.java:834)

at java.util.concurrent.locks.AbstractQueuedSynchronizer.doAcquireInterruptibly(AbstractQueuedSynchronizer.java:894)

at java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireInterruptibly(AbstractQueuedSynchronizer.java:1221)

at java.util.concurrent.locks.ReentrantLock.lockInterruptibly(ReentrantLock.java:340)

at DeadLock.run(DeadLock.java:28)

Locked ownable synchronizers:

- <0x00000007d55ab600> (a java.util.concurrent.locks.ReentrantLock$NonfairSync)

"Service Thread" daemon prio=5 tid=0x00007f8d0c025800 nid=0x4b03 runnable [0x0000000000000000]

java.lang.Thread.State: RUNNABLE

Locked ownable synchronizers:

- None

"C2 CompilerThread1" daemon prio=5 tid=0x00007f8d0c025000 nid=0x4903 waiting on condition [0x0000000000000000]

java.lang.Thread.State: RUNNABLE

Locked ownable synchronizers:

- None

"C2 CompilerThread0" daemon prio=5 tid=0x00007f8d0d01b000 nid=0x4703 waiting on condition [0x0000000000000000]

java.lang.Thread.State: RUNNABLE

Locked ownable synchronizers:

- None

"Signal Dispatcher" daemon prio=5 tid=0x00007f8d0c022000 nid=0x4503 runnable [0x0000000000000000]

java.lang.Thread.State: RUNNABLE

Locked ownable synchronizers:

- None

"Finalizer" daemon prio=5 tid=0x00007f8d0d004000 nid=0x3103 in Object.wait() [0x000000011526a000]

java.lang.Thread.State: WAITING (on object monitor)

at java.lang.Object.wait(Native Method)

- waiting on <0x00000007d5505568> (a java.lang.ref.ReferenceQueue$Lock)

at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:135)

- locked <0x00000007d5505568> (a java.lang.ref.ReferenceQueue$Lock)

at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:151)

at java.lang.ref.Finalizer$FinalizerThread.run(Finalizer.java:189)

Locked ownable synchronizers:

- None

"Reference Handler" daemon prio=5 tid=0x00007f8d0d001800 nid=0x2f03 in Object.wait() [0x0000000115167000]

java.lang.Thread.State: WAITING (on object monitor)

at java.lang.Object.wait(Native Method)

- waiting on <0x00000007d55050f0> (a java.lang.ref.Reference$Lock)

at java.lang.Object.wait(Object.java:503)

at java.lang.ref.Reference$ReferenceHandler.run(Reference.java:133)

- locked <0x00000007d55050f0> (a java.lang.ref.Reference$Lock)

Locked ownable synchronizers:

- None

"VM Thread" prio=5 tid=0x00007f8d0b83b000 nid=0x2d03 runnable

"GC task thread#0 (ParallelGC)" prio=5 tid=0x00007f8d0b818000 nid=0x2503 runnable

"GC task thread#1 (ParallelGC)" prio=5 tid=0x00007f8d0b819000 nid=0x2703 runnable

"GC task thread#2 (ParallelGC)" prio=5 tid=0x00007f8d0d000000 nid=0x2903 runnable

"GC task thread#3 (ParallelGC)" prio=5 tid=0x00007f8d0d001000 nid=0x2b03 runnable

"VM Periodic Task Thread" prio=5 tid=0x00007f8d0c02e800 nid=0x4d03 waiting on condition

JNI global references: 109

Found one Java-level deadlock:

=============================

"north":

waiting for ownable synchronizer 0x00000007d55ab600, (a java.util.concurrent.locks.ReentrantLock$NonfairSync),

which is held by "south"

"south":

waiting for ownable synchronizer 0x00000007d55ab5d0, (a java.util.concurrent.locks.ReentrantLock$NonfairSync),

which is held by "north"

Java stack information for the threads listed above:

===================================================

"north":

at sun.misc.Unsafe.park(Native Method)

- parking to wait for <0x00000007d55ab600> (a java.util.concurrent.locks.ReentrantLock$NonfairSync)

at java.util.concurrent.locks.LockSupport.park(LockSupport.java:186)

at java.util.concurrent.locks.AbstractQueuedSynchronizer.parkAndCheckInterrupt(AbstractQueuedSynchronizer.java:834)

at java.util.concurrent.locks.AbstractQueuedSynchronizer.doAcquireInterruptibly(AbstractQueuedSynchronizer.java:894)

at java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireInterruptibly(AbstractQueuedSynchronizer.java:1221)

at java.util.concurrent.locks.ReentrantLock.lockInterruptibly(ReentrantLock.java:340)

at DeadLock.run(DeadLock.java:48)

"south":

at sun.misc.Unsafe.park(Native Method)

- parking to wait for <0x00000007d55ab5d0> (a java.util.concurrent.locks.ReentrantLock$NonfairSync)

at java.util.concurrent.locks.LockSupport.park(LockSupport.java:186)

at java.util.concurrent.locks.AbstractQueuedSynchronizer.parkAndCheckInterrupt(AbstractQueuedSynchronizer.java:834)

at java.util.concurrent.locks.AbstractQueuedSynchronizer.doAcquireInterruptibly(AbstractQueuedSynchronizer.java:894)

at java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireInterruptibly(AbstractQueuedSynchronizer.java:1221)

at java.util.concurrent.locks.ReentrantLock.lockInterruptibly(ReentrantLock.java:340)

at DeadLock.run(DeadLock.java:28)

Found 1 deadlock.

public class MethodTime {

static java.util.Random r=new java.util.Random();

static Map<String,String> map=null;

static{

map=new HashMap<String,String>();

map.put("1", "Java");

map.put("2", "C++");

map.put("3", "Delphi");

map.put("4", "C");

map.put("5", "Phython");

}

public String getNameById(String id){

try {

Thread.sleep(1);

} catch (InterruptedException e) {

e.printStackTrace();

}

return map.get(id);

}

public List<String> getNamesByIds(String ids){

List<String> re=new ArrayList<String>();

String[] strs=ids.split(",");

for(String id:strs){

re.add(getNameById(id));

}

return re;

}

public List<String> getNamesByIdsBad(String ids){

List<String> re=new ArrayList<String>();

String[] strs=ids.split(",");

for(String id:strs){

//A bad code

getNameById(id);

re.add(getNameById(id));

}

return re;

}

public class NamesByIdsThread implements Runnable{

@Override

public void run() {

try{

while(true){

int c=r.nextInt(4);

String ids="";

for(int i=0;i<c;i++)

ids=Integer.toString((r.nextInt(4)+1))+",";

getNamesByIds(ids);

}

}catch(Exception e){

}

}

}

public class NamesByIdsBadThread implements Runnable{

@Override

public void run() {

try{

while(true){

int c=r.nextInt(4);

String ids="";

for(int i=0;i<c;i++)

ids=Integer.toString((r.nextInt(4)+1))+",";

getNamesByIdsBad(ids);

}

}catch(Exception e){

}

}

}

public static void main(String args[]){

MethodTime instance=new MethodTime();

new Thread(instance.new NamesByIdsThread()).start();

new Thread(instance.new NamesByIdsBadThread()).start();

}

}

import com.sun.btrace.annotations.*;

import static com.sun.btrace.BTraceUtils.*;

@BTrace

public class TracingScript {

@TLS

private static long startTime = 0;

@OnMethod(clazz="/.+/", method="/getNameById/")//监控任意类的getNameById方法

public static void startMethod() {

startTime=timeMillis();

}

@OnMethod(clazz="/.+/", method="/getNameById/",

location=@Location(Kind.RETURN))//方法返回时触发

public static void endMethod() {

print(strcat(strcat(name(probeClass()), "."), probeMethod()));

print(" [");

print(strcat("Time taken : ", str(timeMillis() - startTime)));

println("]");

}

}

MethodTime.getNameById [Time taken : 5]

MethodTime.getNameById [Time taken : 4]

MethodTime.getNameById [Time taken : 7]

MethodTime.getNameById [Time taken : 7]