内容简介：Shallow heap is theRetained set of X is the set of objects which would be removed by GC when X is garbage collected.Retained heap of X is the
Shallow heap is the memory consumed by one object . An object needs 32 or 64 bits (depending on the OS architecture) per reference, 4 bytes per Integer, 8 bytes per Long, etc. Depending on the heap dump format the size may be adjusted (e.g. aligned to 8, etc…) to model better the real consumption of the VM.
Retained Set
Retained set of X is the set of objects which would be removed by GC when X is garbage collected.
Retained Heap
Retained heap of X is the sum of shallow sizes of all objects in the retained set of X , i.e. memory kept alive by X.
Generally speaking, shallow heap of an object is its size in the heap and retained size of the same object is the amount of heap memory that will be freed when the object is garbage collected .
The Minimum Retained Size gives a good (under)estimation of the retained size which is calculated ways faster than the exact retained size of a set of objects. It only depends on the number of objects in the inspected set , not the number of objects in the heap dump.
Dominator Tree
Memory Analyzer provides a dominator tree of the object graph. The transformation of the object reference graph into a dominator tree allows you to easily identify the biggest chunks of retained memory and the keep-alive dependencies among objects .
Dominate
An object x dominates an object y if every path in the object graph from the start (or the root) node to y must go through x.
Immediate Dominator
The immediate dominator x of some object y is the dominator closest to the object y.
Properties
- The objects belonging to the sub-tree of x (i.e. the objects dominated by x) represent the retained set of x.
- If x is the immediate dominator of y , then the immediate dominator of x also dominates y , and so on.
- The edges in the dominator tree do not directly correspond to object references from the object graph.
A dominator tree is built out of the object graph. In the dominator tree each object is the immediate dominator of its children , so dependencies between the objects are easily identified.
Overview
Dominator Tree
No Grouping(Objects)
Group By Class
Group By Class Loader
纬度：组件
Group By Package
纬度：自身编写的代码
Path To GC Roots
Histogram
MAT默认按 Shallow Heap 倒排，手动选择按 Retained Heap 倒排，排第一的是 Ehcache 的 OnHeapStore 类
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数字化生存
（美）Nicholas Negroponte（尼古拉·尼葛洛庞帝） / 胡泳、范海燕 / 电子工业出版社 / 2017-1-1 / 68.00
《数字化生存》描绘了数字科技为我们的生活、工作、教育和娱乐带来的各种冲击和其中值得深思的问题，是跨入数字化新世界的*指南。英文版曾高居《纽约时报》畅销书排行榜。 “信息的DNA”正在迅速取代原子而成为人类生活中的基本交换物。尼葛洛庞帝向我们展示出这一变化的巨大影响。电视机与计算机屏幕的差别变得只是大小不同而已。从前所说的“大众”传媒正演变成个人化的双向交流。信息不再被“推给”消费者，相反，人们或他......一起来看看 《数字化生存》 这本书的介绍吧!
