为什么空Java程序消耗内存？ [英] Why does an empty Java program consume memory?

问题描述

我正在探索Java中的内存使用情况，以了解我的程序泄漏内存的原因。在我的main while循环中剥离代码之后，我仍然会随着时间的推移增加内存使用量。思考空程序的内存使用情况：

I'm exploring memory usage in Java to understand why my program leaks memory. After stripping off code in my main while loop, I still get an increase of memory usage over time. Pondering the memory usage of an empty program:

class Nothing
{    public static void main(String[] args)
     {    while(true);    }
}

我仍看到内存增加：

所以我的问题是：为什么还有锯齿形？为什么当GC运行时它没有保存所有内存（每次gc运行（谷值）使用的内存增加10-20Kb（与之前的谷值相比））？

So my question is: Why is there still a saw tooth pattern? Why when the GC runs does it not save all the memory (each time the gc runs (the valleys) the used memory increases by 10-20Kb (compared to the previous valley))?

编辑：

java版1.6.0_29

java version "1.6.0_29"

Java（TM）SE运行时环境（版本1.6.0_29-b11）

Java(TM) SE Runtime Environment (build 1.6.0_29-b11)

Java HotSpot（TM）客户端VM（版本20.4-b02，混合模式，共享）

Java HotSpot(TM) Client VM (build 20.4-b02, mixed mode, sharing)

OS：Windows 7 Enterprise-32位

OS: Windows 7 Enterprise-32 bit

推荐答案

为什么还有锯齿形？

Why is there still a saw tooth pattern?

如果我没弄错的话，部分原因是监视器本身正在强制应用程序创建临时对象，其中包含有关垃圾收集和内存使用状态的信息。

If I'm not mistaken, part of the reason for this is that the monitor itself is forcing the application to create temporary objects that contain information about the state of garbage-collection and memory usage.

为什么当GC运行不会保存所有内存（每次gc运行（谷值）使用的内存增加10-20Kb（与previ相比） ous valley））？

Why when the GC runs does it not save all the memory (each time the gc runs (the valleys) the used memory increases by 10-20Kb (compared to the previous valley))?

我相信显示器在垃圾收集后不会立即看到已用内存的数量，而是必须经常轮询以查看内存使用情况。因此，感知的山谷必然略高于真正的山谷。我会猜测，谷底内存使用量的感知增加只是这种差异的随机误差，并且随着时间的推移会被中和。 （也就是说，我不认为每个周期实际上有10-20 KB的内存泄漏。）

I believe the monitor does not instantly see the amount of used memory after garbage-collection, but rather, must poll frequently to see memory usage. Therefore, the perceived "valley" is necessarily somewhat higher than the true valley. I would guess that the perceived increase in memory usage at the valleys is just a random artifact of this discrepancy, and would be neutralized over time. (That is, I don't think that there's actually 10-20 KB of memory leak occurring in each cycle.)

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