linux中查找java程序 cpu佔用高的代碼位置。

一：測試運行代碼：

package com.wang;

public class Main {
	public static void  main(String[] args) {
		System.out.print(1);
		new Main().run();
	}
	public void run(){
		int i=1;
		for(;;){
			for(;;){
				i++;
			}
		}
	}
}

二：在linux中運行這段代碼：然後用top就會看到cpu高的進程id 6375

PID 1	USER	1	PR	NI	VIRT	RES	SHR	S	%CPU	%MEM	TIME+	COMMAND
6375	user1	1	20	0	2150964	25300	14880	S	88.7	2.5	0:22.72	java

三：查看進程中的線程 ps -mp 6375 -o THREAD,tid,time

USER	%CPU	PRI	SCNT	WCHAH	USER	SYSTEM	TID	TIME
user1	86.3	19	-	-	-	-	6379	00:05:16

四：轉儲線程快照

• （./jstack 6375 > 6375）這裏的6375是線程id
• 可以看到三中線程消耗cpu最高的是6379 轉化爲16進制是18eb。然後看四

五：在四中產生的轉儲文件（如下）找18eb這個線程。線程的調用棧就是代碼中的i++;

2016-11-01 05:49:59
Full thread dump Java HotSpot(TM) 64-Bit Server VM (25.111-b14 mixed mode):

"Attach Listener" #8 daemon prio=9 os_prio=0 tid=0x00007ffa44001000 nid=0x1900 waiting on condition [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE

"Service Thread" #7 daemon prio=9 os_prio=0 tid=0x00007ffa6c0ce000 nid=0x18f3 runnable [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE

"C1 CompilerThread1" #6 daemon prio=9 os_prio=0 tid=0x00007ffa6c0b1000 nid=0x18f2 waiting on condition [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE

"C2 CompilerThread0" #5 daemon prio=9 os_prio=0 tid=0x00007ffa6c0af000 nid=0x18f1 waiting on condition [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE

"Signal Dispatcher" #4 daemon prio=9 os_prio=0 tid=0x00007ffa6c0ad800 nid=0x18f0 runnable [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE

"Finalizer" #3 daemon prio=8 os_prio=0 tid=0x00007ffa6c07a000 nid=0x18ef in Object.wait() [0x00007ffa5c6fd000]
   java.lang.Thread.State: WAITING (on object monitor)
	at java.lang.Object.wait(Native Method)
	- waiting on <0x00000000f0c08e98> (a java.lang.ref.ReferenceQueue$Lock)
	at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:143)
	- locked <0x00000000f0c08e98> (a java.lang.ref.ReferenceQueue$Lock)
	at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:164)
	at java.lang.ref.Finalizer$FinalizerThread.run(Finalizer.java:209)

"Reference Handler" #2 daemon prio=10 os_prio=0 tid=0x00007ffa6c075800 nid=0x18ee in Object.wait() [0x00007ffa5c7fe000]
   java.lang.Thread.State: WAITING (on object monitor)
	at java.lang.Object.wait(Native Method)
	- waiting on <0x00000000f0c06b40> (a java.lang.ref.Reference$Lock)
	at java.lang.Object.wait(Object.java:502)
	at java.lang.ref.Reference.tryHandlePending(Reference.java:191)
	- locked <0x00000000f0c06b40> (a java.lang.ref.Reference$Lock)
	at java.lang.ref.Reference$ReferenceHandler.run(Reference.java:153)

"main" #1 prio=5 os_prio=0 tid=0x00007ffa6c009800 nid=0x18eb runnable [0x00007ffa73870000]
   java.lang.Thread.State: RUNNABLE
	at com.wang.Main.run(Main.java:11)
	at com.wang.Main.main(Main.java:6)

"VM Thread" os_prio=0 tid=0x00007ffa6c06e000 nid=0x18ed runnable 

"VM Periodic Task Thread" os_prio=0 tid=0x00007ffa6c0d1800 nid=0x18f4 waiting on condition 

JNI global references: 9