为什么 Lua 使用垃圾收集器而不是引用计数? [英] Why does Lua use a garbage collector instead of reference counting?

问题描述

我自己听说并体验过:随着脚本部分的增长，Lua 的垃圾收集器会导致游戏的 FPS 严重下降.

I've heard and experienced it myself: Lua's garbage collector can cause serious FPS drops in games as their scripted part grows.

这是我发现的与垃圾收集器相关的内容，例如，在其中创建的每个 Vector() 用户数据对象都暂时存在，直到被垃圾收集为止.

This is as I found out related to the garbage collector, where for example every Vector() userdata object created temporarily lies around until getting garbage collected.

我知道 Python 使用引用计数，这就是为什么它不需要像 Luas GC 那样庞大的、消耗性能的步骤.

I know that Python uses reference counting, and that is why it doesn't need any huge, performance eating steps like Luas GC has to do.

• 为什么 Lua 不使用引用计数来清除垃圾?

推荐答案

因为引用计数垃圾收集器很容易泄漏对象.

Because reference counting garbage collectors can easily leak objects.

简单的例子:双向链表.每个节点都有一个指向下一个节点的指针 - 并且下一个节点指向它本身.如果你只是取消引用列表本身并期望它被收集，你就泄露了整个列表 - none 节点的引用计数为零，因此它们都会相互保留活.使用引用计数垃圾收集器，任何时候你有一个循环对象，你基本上都需要把它当作一个非托管对象，并在你完成后自己明确地处理它.

Trivial example: a doubly-linked list. Each node has a pointer to the next node - and is itself pointed to by the next one. If you just un-reference the list itself and expect it to be collected, you just leaked the entire list - none of the nodes have a reference count of zero, and hence they'll all keep each other alive. With a reference counting garbage collector, any time you have a cyclic object, you basically need to treat that as an unmanaged object and explicitly dispose of it yourself when you're finished.

请注意，除了引用计数之外，Python 还使用了适当的垃圾收集器.

Note that Python uses a proper garbage collector in addition to reference counting.

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