.net - 垃圾收集发生在进程级别还是应用程序域级别？

Question

FullGC 通常会在运行时暂停所有线程。有两个 AppDomain，每个都运行多个线程。 GC 运行时，是所有线程都暂停，还是仅暂停其中一个 AppDomain 的线程？

Answer 1

很难回答，最好的办法就是测试一下:

using System;
using System.Reflection;

public class Program : MarshalByRefObject {
    static void Main(string[] args) {
        var dummy1 = new object();
        var dom = AppDomain.CreateDomain("test");
        var obj = (Program)dom.CreateInstanceAndUnwrap(Assembly.GetExecutingAssembly().FullName, typeof(Program).FullName);
        obj.Test();
        Console.WriteLine("Primary appdomain, collection count = {0}, gen = {1}",
            GC.CollectionCount(0), GC.GetGeneration(dummy1));
        Console.ReadKey();

    }
    public void Test() {
        var dummy2 = new object();
        for (int test = 0; test < 3; ++test) {
            GC.Collect();
            GC.WaitForPendingFinalizers();
        } 
        Console.WriteLine("In appdomain '{0}', collection count = {1}, gen = {2}",
            AppDomain.CurrentDomain.FriendlyName, GC.CollectionCount(0),
            GC.GetGeneration(dummy2));
    }
}

输出:

In appdomain 'test', collection count = 3, gen = 2
Primary appdomain, collection count = 3, gen = 2

很好的证据表明 GC 会影响默认 CLR 主机上的所有 AppDomain。这让我很惊讶。