Bug 4189 - Delegate invocation over value type is slow
Summary: Delegate invocation over value type is slow
Status: RESOLVED FIXED
Alias: None
Product: Runtime
Classification: Mono
Component: JIT ()
Version: unspecified
Hardware: PC Linux
: --- normal
Target Milestone: ---
Assignee: Bugzilla
URL:
Depends on:
Blocks:
 
Reported: 2012-04-02 13:26 UTC by Marek Safar
Modified: 2013-08-23 12:59 UTC (History)
4 users (show)

Tags:
Is this bug a regression?: ---
Last known good build:

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Status:
RESOLVED FIXED

Description Marek Safar 2012-04-02 13:26:45 UTC
using System;
using System.Diagnostics;

namespace BoxingTest
{
	public interface ICriticalNotifyCompletion
	{
		void UnsafeOnCompleted(Action a);
	}

	public interface IAsyncStateMachine
	{
		void MoveNext();
	}

	struct Awaiter : ICriticalNotifyCompletion
	{
		public void UnsafeOnCompleted(Action a)
		{
			a();
		}
	}

	public struct AsyncVoidMethodBuilder
	{
		public void AwaitUnsafeOnCompleted<TAwaiter, TStateMachine>(ref TAwaiter awaiter, ref TStateMachine stateMachine)
			where TAwaiter : ICriticalNotifyCompletion
			where TStateMachine : IAsyncStateMachine
		{
			var action = new Action(stateMachine.MoveNext);
			awaiter.UnsafeOnCompleted(action);
		}
	}

	struct Test : IAsyncStateMachine
	{
		public static int counter;

		public void MoveNext()
		{
			++counter;
		}

		public void Entry ()
		{
			var s = new AsyncVoidMethodBuilder();
			var awaiter = new Awaiter();
			s.AwaitUnsafeOnCompleted(ref awaiter, ref this);
		}
	}

	class Program
	{
		static void Main(string[] args)
		{
			var sw = new Stopwatch();
			sw.Start();
			for (int i = 0; i < 1000000; ++i)
			{
				new Test().Entry();
			}

			sw.Stop();
			//Console.WriteLine(GC.GetTotalMemory(false));
			Console.WriteLine(sw.ElapsedMilliseconds);
			Console.WriteLine(Test.counter);
		}
	}
}

On amd64

.NET: ~150 (but also 40 in one of 3 runs)
Mono: ~1500 (~650 with sgen)
Comment 1 Zoltan Varga 2012-04-03 02:12:10 UTC
The generics stuff in AwaitUnsafeOnCompleted forces us to skip the optimized code path for delegate creation, so we go through the slower path in mono_delegate_trampoline (), which accounts for a large part of the slowdown in this testcase.
Comment 2 Rodrigo Kumpera 2013-08-23 12:59:08 UTC
We now use delegate fast path in generic code too.