常见内存调优工具介绍及使用

我会带着你远行 2023-02-21 06:34 116阅读 0赞

内存调优问题是面试过程中常被问到的问题,这篇文章就简单了解一下有哪些内存调优的工具 ,常见问题如下:  
1,实际开发过程中你遇到过什么问题?你是如何解决的?  
2,实际项目上线之后,如果出现了卡顿现象,你是如何分析,如何解决的?  
3,你有用过内存诊断工具吗?  
4,实际开发中你是如何进行GC调优的?  
5,垃圾回收之后,内存占用仍然很高.该如何分析?  
6,如何查看堆内存中对象的个数?  
7,线上环境JVM排查与dump日志排查有做过吗?  
常见的内存诊断工具如下表:  
工具 含义  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3Noa3N0YXJ0_size_16_color_FFFFFF_t_70_pic_center]  
案例code

//jmap命令 通过断点形式演示
    public class JmapTest { 
        @SuppressWarnings("unused")
        public static void main(String[] args) { 
            System.out.println("1.......");
            
            System.out.println("begin....");
            
            byte[] array = new byte[1024*1024*10];  //10MB 监测是堆内存使用情况
            
            System.out.println("2........");
            
            System.out.println("mid....");
            
            array = null;
            
            System.gc();
            
            System.out.println("3........");
    
            System.out.println("end........");
        }
    }
    
    //jvisualvm 命令
    public class LhdDemo { 
    
        public static void main(String[] args) throws Exception { 
            List<Student> students = new ArrayList<Student>();
            for (int i = 0; i < 200; i++) { 
                students.add(new Student());
            }
            Thread.sleep(1000000000L);
            
        }
    
    }
    class Student{ 
        private byte[] big = new byte[1024*1024];
    }
    //visualvm 插件案例
    public class GcDemo { 
    
        public static void main(String[] args) { 
            List<byte[]> list = new ArrayList<byte[]>();
    
            int i = 0;
    
            boolean flag = true;
    
            while (flag) { 
                try { 
                    i++;
                    list.add(new byte[1024*1024]); // 每次增加1M
                    Thread.sleep(70);
                } catch (Throwable e) { 
                    e.printStackTrace();
                    flag = false;
                    System.out.println("count..." + i);
                }
            }
        }
    }

需要安装插件:  
com-sun-tools-visualvm-modules-visualgc\_1  
步骤:  
第一步:  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3Noa3N0YXJ0_size_16_color_FFFFFF_t_70_pic_center 1]  
第二步  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3Noa3N0YXJ0_size_16_color_FFFFFF_t_70_pic_center 2]  
第三步  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3Noa3N0YXJ0_size_16_color_FFFFFF_t_70_pic_center 3]  
第四步:  
![在这里插入图片描述][20200629123247282.png_pic_center]  
第五步:  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3Noa3N0YXJ0_size_16_color_FFFFFF_t_70_pic_center 4]

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[20200629123247282.png_pic_center]: https://img-blog.csdnimg.cn/20200629123247282.png#pic_center
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