openjdk8 使用 hsdb 工具追踪内存中的对象

梦里梦外; 2023-01-17 12:52 116阅读 0赞

调试的源代码

package test;
    
    public class JHSDB_TestCase {
    	
    	private static class ObjectHolder{}
    	
    	static class Test{
    		static ObjectHolder staticObj = new ObjectHolder();
    		ObjectHolder instanceObj = new ObjectHolder(); 
    		
    		// 忽略变量未使用的警告
    		@SuppressWarnings("unused")
    		void foo() {
    			ObjectHolder localObj = new ObjectHolder();
    			// 这里需要打个断点
    			System.out.println("done");
    		}
    	}
    
    	public static void main(String[] args) {
    		Test test = new JHSDB_TestCase.Test();
    		test.foo();
    	}
    
    }

调试参数

\-Xmx10m -XX:-UseCompressedOops

运行cmd控制台

查看程序JVMID  
jps -l

![20210429135241110.png][]

打开hsdb工具

hsdb 8524

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3h6bEF3aW4_size_16_color_FFFFFF_t_70][]

\[Tools\] → \[Heap Parameters\]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3h6bEF3aW4_size_16_color_FFFFFF_t_70 1][]

\[Windows\] → \[Console\]  
\# 语法：scanoops \[eden起始地址\] \[to终止地址\] \[包名.类名$变量名\]  
scanoops 0x0000000012500000 0x0000000012700000 test.JHSDB\_TestCase$ObjectHolder

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3h6bEF3aW4_size_16_color_FFFFFF_t_70 2][]

\# 查看栈中存放的数据  
\[Windows\] → \[Console\]  
revptrs 0x00000000125e4440  
显示  
null  
Oop for java/lang/Class @ 0x00000000125e2448

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3h6bEF3aW4_size_16_color_FFFFFF_t_70 3][]

\# 查看栈中存放的数据

\[Windows\] → \[Console\]  
revptrs 0x00000000125e4468  
显示  
Oop for test/JHSDB\_TestCase$Test @ 0x00000000125e4450

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3h6bEF3aW4_size_16_color_FFFFFF_t_70 4][]

\# 监控内存中地址的数据，0x00000000125e4450  
\[Tools\] → \[Inspector\]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3h6bEF3aW4_size_16_color_FFFFFF_t_70 5][]

\# 查看栈中存放的数据  
\[Windows\] → \[Console\]  
revptrs 0x00000000125e4478  
显示  
Computing reverse pointers...  
Done.  
null  
null

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3h6bEF3aW4_size_16_color_FFFFFF_t_70 6][]

\# 选择主线程  
点击\[Java Thread Name\] → \[main\]  
\# 查看栈中数据  
点击工具栏\[Stack Memory\]，可以看到  
0x00000000125e4478 PSYoungGen test/JHSDB\_TestCase$ObjectHolder

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3h6bEF3aW4_size_16_color_FFFFFF_t_70 7][]

实验完成，调试代码中ObjectHolder三个对象均已找到，并成功追  
溯到引用它们的地方，也就实践验证ObjectHolder存放在虚拟机内存的栈和堆中。

[20210429135241110.png]: /images/20221021/b5b3bea532af4ba2a1a63169fbc48a53.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3h6bEF3aW4_size_16_color_FFFFFF_t_70]: /images/20221021/5edcf3eb3a354340ba2e6b57668ca397.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3h6bEF3aW4_size_16_color_FFFFFF_t_70 1]: /images/20221021/6c2772f079dc4909a78f2488e248bb89.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3h6bEF3aW4_size_16_color_FFFFFF_t_70 2]: /images/20221021/8226bfe90ccc4f6cbb87ffc26d0b69aa.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3h6bEF3aW4_size_16_color_FFFFFF_t_70 3]: /images/20221021/fa8cda31c4ff4163b15cc20b0884c2e2.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3h6bEF3aW4_size_16_color_FFFFFF_t_70 4]: /images/20221021/56a95d9503ee4d15a45a30335bd3753b.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3h6bEF3aW4_size_16_color_FFFFFF_t_70 5]: /images/20221021/967ffd2ba5794b33a2a0d1e11bfe8fdb.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3h6bEF3aW4_size_16_color_FFFFFF_t_70 6]: /images/20221021/968fd47578614287a5a8ce02dbd72664.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3h6bEF3aW4_size_16_color_FFFFFF_t_70 7]: /images/20221021/44eabe3d2e504282b9d9f48e64765a89.png