由于freeMemory()仅报告长期存在的对象，因此如何跟踪Java中的任何对象创建? [英] How to track any object creation in Java since freeMemory() only reports long-lived objects?

问题描述

每当我的JVM创建一个新对象时，我都希望在日志中打印一些内容.我试图使用Runtime.getRuntime().freeMemory()进行检测，但不幸的是，直到将其提升到堆之前，它都没有考虑任何短期对象(

Whenever a new object is created by my JVM I want to print something in the log. I was trying to detect that using Runtime.getRuntime().freeMemory() but unfortunately it does NOT take into account any short-lived object until it is promoted to the heap (check here for more details).

那么，有人知道我的JVM实例化/创建对象时如何检测/跟踪吗?为了简化操作，我们如何完成以下代码:

So does anyone know how to detect/track whenever an object is instantiated/created by my JVM? To make it easier, how do we complete the code below:

随意使用MemoryPoolMXBean和JMX:

public class MemoryUtils {

    private static Set<String> set = new HashSet<String>();

    public static void main(String[] args) {

        // START

        // now create a bunch of objects and save them in the set
        for (int i = 0; i < 100; i++) {
            set.add(new String("foo" + i));
        }

        // FINISH

        // FIXME: Do something here to detect that a bunch of objects were created!

    }
}

以下是弗拉基米尔(Vladimir)提出的尝试解决方案:

Trying solution proposed by Vladimir below:

它可以工作，但是有一个奇怪的副作用:

It works, but with a weird side-effect:

long t = totalThreadMemoryAllocated();

// did nothing

t = totalThreadMemoryAllocated() - t;

System.out.println(t); // ==> 48 !!!???

public static long totalThreadMemoryAllocated() {
    com.sun.management.ThreadMXBean tBean = (com.sun.management.ThreadMXBean) ManagementFactory.getThreadMXBean();
    return tBean.getThreadAllocatedBytes(Thread.currentThread().getId());
}

但是它确实说明了任何对象的创建，所以我猜想如果我从中减去幻数48可以使用它.

But it DOES account for any object creation so I guess I could use this if I subtract the magic number 48 from it.

推荐答案

您可以使用Java代理来执行此操作，可以通过作者的博客找到开放源代码实现-

you can use a Java agent to do this, open source implementation can be found via the author's blog - http://jeremymanson.blogspot.co.uk/2012/02/update-to-allocation-instrumenter.html

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