c# - 为什么垃圾收集器只有 3 代，不多也不少？

Question

因为我经历了垃圾收集 (GC) 及其代(0,1,2)。 我突然想到一个问题，为什么 Microsoft 决定将其保留为 3？

为什么不要少于 3 或多于 3？我需要一些合乎逻辑的解释。

Answer 1

引用文档，

Generations

The heap is organized into generations so it can handle long-lived and short-lived objects. Garbage collection primarily occurs with the reclamation of short-lived objects that typically occupy only a small part of the heap. There are three generations of objects on the heap:

Generation 0.

This is the youngest generation and contains short-lived objects. An example of a short-lived object is a temporary variable. Garbage collection occurs most frequently in this generation.

Newly allocated objects form a new generation of objects and are implicitly generation 0 collections, unless they are large objects, in which case they go on the large object heap in a generation 2 collection.

Most objects are reclaimed for garbage collection in generation 0 and do not survive to the next generation.

Generation 1.

This generation contains short-lived objects and serves as a buffer between short-lived objects and long-lived objects.

Generation 2.

This generation contains long-lived objects. An example of a long-lived object is an object in a server application that contains static data that is live for the duration of the process.

Garbage collections occur on specific generations as conditions warrant. Collecting a generation means collecting objects in that generation and all its younger generations. A generation 2 garbage collection is also known as a full garbage collection, because it reclaims all objects in all generations (that is, all objects in the managed heap).

我们可以看到，第 2 代 适用于应在整个过程中持续存在的对象。为比进程生命周期更长的对象建模是不明智的，至少在我所知道的操作系统上是这样。

我怀疑没有更大的世代粒度，因为它会证明比派生的好处更麻烦。对这个概念的任何推断都是纯粹的猜测，没有进行真实世界的性能测试。

我怀疑即使是来自 GC 设计者的规范答案也容易引起猜测，但他们可能能够详细说明该粒度级别是如何计算的。