符号垃圾收集 Ruby 2.2.1

Question

所以从 Ruby 2.2+ 版本引入了符号垃圾收集。我在 irb 中写了以下代码片段：

before =  Symbol.all_symbols.size #=>3331
100_000.times do |i|
  "sym#{i}".to_sym
end

Symbol.all_symbols.size #=> 18835
GC.start
Symbol.all_symbols.size #=>3331

因此，正如预期的那样，它收集了使用 to_sym 动态生成的所有符号。

那么 GC 是如何知道收集哪些符号的呢？即使它们在程序中被引用，它会收集符号吗？符号垃圾回收是如何工作的？如果我创建的其中一个符号在程序中被引用，它还会收集它吗？

我正在使用 Ruby 2.2.1。

Answer 1

Basically, all symbols created dynamically while Ruby is running (via to_sym, etc.) can be garbage collected because they are not being used behind the scenes inside the Ruby interpreter. However, symbols created as a result of creating a new method or symbols that are statically inside of code will not be garbage collected. For example :foo and def foo; end both will not be garbage collected, however "foo".to_sym would be eligible for garbage collection.

参考Richard Schneeman's post。

符号垃圾收集 Ruby 2.2.1

Garbage Collection of Symbols Ruby 2.2.1

ruby

garbage-collection

ruby-2.2