JVM 调优实战--一个案例理解常用工具（命令）

清疚 2023-10-07 08:21 30阅读 0赞

> 测试代码

import java.math.BigDecimal;
    import java.util.ArrayList;
    import java.util.Date;
    import java.util.List;
    import java.util.concurrent.ScheduledThreadPoolExecutor;
    import java.util.concurrent.ThreadPoolExecutor;
    import java.util.concurrent.TimeUnit;
    
    /**
     * 从数据库中读取信用数据，套用模型，并把结果进行记录和传输
     */
    
    public class T15_FullGC_Problem01 {
    
        private static class CardInfo {
            BigDecimal price = new BigDecimal(0.0);
            String name = "张三";
            int age = 5;
            Date birthdate = new Date();
    
            public void m() {}
        }
    
        private static ScheduledThreadPoolExecutor executor = new ScheduledThreadPoolExecutor(50,
                new ThreadPoolExecutor.DiscardOldestPolicy());
    
        public static void main(String[] args) throws Exception {
            executor.setMaximumPoolSize(50);
    
            for (;;){
                modelFit();
                Thread.sleep(100);
            }
        }
    
        private static void modelFit(){
            List<CardInfo> taskList = getAllCardInfo();
            taskList.forEach(info -> {
                // do something
                executor.scheduleWithFixedDelay(() -> {
                    //do sth with info
                    info.m();
    
                }, 2, 3, TimeUnit.SECONDS);
            });
        }
    
        private static List<CardInfo> getAllCardInfo(){
            List<CardInfo> taskList = new ArrayList<>();
    
            for (int i = 0; i < 100; i++) {
                CardInfo ci = new CardInfo();
                taskList.add(ci);
            }
    
            return taskList;
        }
    }

> 1.  java -Xms200M -Xmx200M com.mashibing.jvm.gc.T15\_FullGC\_Problem01
> 2.  top命令观察到问题：内存不断增长 CPU占用率居高不下
> 3.  jps定位具体java进程
> 4.  jinfo pid
> 5.  jstat -gc 动态观察gc情况 / 阅读GC日志发现频繁GC / arthas观察 / jconsole jstat -gc 4655 500 : 每个500个毫秒打印GC的情况
> 6.  jmap - histo 4655 | head -20，查找有多少对象产生
> 7.  jmap -dump:format=b,file=xxx pid / jmap -histo
> 8.  java -Xms20M -Xmx20M -XX:+UseParallelGC -XX:+HeapDumpOnOutOfMemoryError com.mashibing.jvm.gc.T15\_FullGC\_Problem01
> 9.  使用MAT / jhat进行dump文件分析 [https://www.cnblogs.com/baihuitestsoftware/articles/6406271.html][https_www.cnblogs.com_baihuitestsoftware_articles_6406271.html]
> 10. 找到代码的问题

[https_www.cnblogs.com_baihuitestsoftware_articles_6406271.html]: https://www.cnblogs.com/baihuitestsoftware/articles/6406271.html