Performances d'Expression: Compilation vs Lambda, appels directs vs appels virtuels
Je suis curieux de voir à quel point la Expression.Compile est performante par rapport à l'expression lambda dans le code et par rapport à l'utilisation directe de méthode, et aussi par les appels de méthode directs par rapport aux appels de méthode virtuelle (pseudo-code):
var foo = new Foo();
var iFoo = (IFoo)foo;
foo.Bar();
iFoo.Bar();
(() => foo.Bar())();
(() => iFoo.Bar())();
Expression.Compile(foo, Foo.Bar)();
Expression.Compile(iFoo, IFoo.Bar)();
Expression.CompileToMethod(foo, Foo.Bar);
Expression.CompileToMethod(iFoo, IFoo.Bar);
MethodInfo.Invoke(foo, Foo.Bar);
MethodInfo.Invoke(iFoo, IFoo.Bar);
Je n'ai trouvé aucune réponse, voici donc le test de performance:
using System;
using System.Diagnostics;
using System.Linq.Expressions;
using System.Reflection;
using System.Reflection.Emit;
namespace ExpressionTest
{
public interface IFoo
{
int Bar();
}
public sealed class FooImpl : IFoo
{
public int Bar()
{
return 0;
}
}
class Program
{
static void Main(string[] args)
{
var foo = new FooImpl();
var iFoo = (IFoo)foo;
Func<int> directLambda = () => foo.Bar();
Func<int> virtualLambda = () => iFoo.Bar();
var compiledDirectCall = CompileBar(foo, asInterfaceCall: false);
var compiledVirtualCall = CompileBar(foo, asInterfaceCall: true);
var compiledArgDirectCall = CompileBar<FooImpl>();
var compiledArgVirtualCall = CompileBar<IFoo>();
var barMethodInfo = typeof(FooImpl).GetMethod(nameof(FooImpl.Bar));
var iBarMethodInfo = typeof(IFoo).GetMethod(nameof(IFoo.Bar));
var compiledToModuleDirect = CompileToModule<FooImpl>();
var compiledToModuleVirtual = CompileToModule<IFoo>();
var iterationCount = 200000000;
Console.WriteLine($"Iteration count: {iterationCount:N0}");
var sw = Stopwatch.StartNew();
for (int i = 0; i < iterationCount; i++)
compiledVirtualCall();
var elapsedMs = sw.ElapsedMilliseconds;
Console.WriteLine($"Virtual (Func<int>)Expression.Compile(): {elapsedMs} ms");
sw.Restart();
for (int i = 0; i < iterationCount; i++)
compiledDirectCall();
elapsedMs = sw.ElapsedMilliseconds;
Console.WriteLine($"Direct (Func<int>)Expression.Compile(): {elapsedMs} ms");
sw.Restart();
for (int i = 0; i < iterationCount; i++)
compiledArgVirtualCall(iFoo);
elapsedMs = sw.ElapsedMilliseconds;
Console.WriteLine($"Virtual (Func<IFoo, int>)Expression.Compile(): {elapsedMs} ms");
sw.Restart();
for (int i = 0; i < iterationCount; i++)
compiledArgDirectCall(foo);
elapsedMs = sw.ElapsedMilliseconds;
Console.WriteLine($"Direct (Func<FooImpl, int>)Expression.Compile(): {elapsedMs} ms");
sw.Restart();
for (int i = 0; i < iterationCount; i++)
compiledToModuleVirtual(iFoo);
elapsedMs = sw.ElapsedMilliseconds;
Console.WriteLine($"Virtual (Func<IFoo, int>)Expression.CompileToMethod(): {elapsedMs} ms");
sw.Restart();
for (int i = 0; i < iterationCount; i++)
compiledToModuleDirect(foo);
elapsedMs = sw.ElapsedMilliseconds;
Console.WriteLine($"Direct (Func<FooImpl, int>)Expression.CompileToMethod(): {elapsedMs} ms");
sw.Restart();
for (int i = 0; i < iterationCount; i++)
virtualLambda();
elapsedMs = sw.ElapsedMilliseconds;
Console.WriteLine($"Virtual () => IFoo.Bar(): {elapsedMs} ms");
sw.Restart();
for (int i = 0; i < iterationCount; i++)
directLambda();
elapsedMs = sw.ElapsedMilliseconds;
Console.WriteLine($"Direct () => FooImpl.Bar(): {elapsedMs} ms");
sw.Restart();
for (int i = 0; i < iterationCount; i++)
iFoo.Bar();
elapsedMs = sw.ElapsedMilliseconds;
Console.WriteLine($"Virtual IFoo.Bar(): {elapsedMs} ms");
sw.Restart();
for (int i = 0; i < iterationCount; i++)
foo.Bar();
elapsedMs = sw.ElapsedMilliseconds;
Console.WriteLine($"Direct Foo.Bar(): {elapsedMs} ms");
sw.Restart();
for (int i = 0; i < iterationCount; i++) {
int result = (int)iBarMethodInfo.Invoke(iFoo, null);
}
elapsedMs = sw.ElapsedMilliseconds;
Console.WriteLine($"Virtual MethodInfo.Invoke(FooImpl, Bar): {elapsedMs} ms");
sw.Restart();
for (int i = 0; i < iterationCount; i++) {
int result = (int)barMethodInfo.Invoke(foo, null);
}
elapsedMs = sw.ElapsedMilliseconds;
Console.WriteLine($"Direct MethodInfo.Invoke(IFoo, Bar): {elapsedMs} ms");
}
static Func<int> CompileBar(IFoo foo, bool asInterfaceCall)
{
var fooType = asInterfaceCall ? typeof(IFoo) : foo.GetType();
var methodInfo = fooType.GetMethod(nameof(IFoo.Bar));
var instance = Expression.Constant(foo, fooType);
var call = Expression.Call(instance, methodInfo);
var lambda = Expression.Lambda(call);
var compiledFunction = (Func<int>)lambda.Compile();
return compiledFunction;
}
static Func<TInput, int> CompileBar<TInput>()
{
var fooType = typeof(TInput);
var methodInfo = fooType.GetMethod(nameof(IFoo.Bar));
var instance = Expression.Parameter(fooType, "foo");
var call = Expression.Call(instance, methodInfo);
var lambda = Expression.Lambda(call, instance);
var compiledFunction = (Func<TInput, int>)lambda.Compile();
return compiledFunction;
}
static Func<TInput, int> CompileToModule<TInput>()
{
var fooType = typeof(TInput);
var methodInfo = fooType.GetMethod(nameof(IFoo.Bar));
var instance = Expression.Parameter(fooType, "foo");
var call = Expression.Call(instance, methodInfo);
var lambda = Expression.Lambda(call, instance);
var asmName = new AssemblyName(fooType.Name);
var asmBuilder = AssemblyBuilder.DefineDynamicAssembly(asmName, AssemblyBuilderAccess.Run);
var moduleBuilder = asmBuilder.DefineDynamicModule(fooType.Name);
var typeBuilder = moduleBuilder.DefineType(fooType.Name, TypeAttributes.Public);
var methodBuilder = typeBuilder.DefineMethod(nameof(IFoo.Bar), MethodAttributes.Static, typeof(int), new[] { fooType });
Expression.Lambda<Action>(lambda).CompileToMethod(methodBuilder);
var createdType = typeBuilder.CreateType();
var mi = createdType.GetMethods(BindingFlags.NonPublic | BindingFlags.Static)[1];
var func = Delegate.CreateDelegate(typeof(Func<TInput, int>), mi);
return (Func<TInput, int>)func;
}
}
}
Sur mon ordinateur portable (mode Release, 64 bits, .NET 4.5.2), cela donne:
Iteration count: 200,000,000
Virtual MethodInfo.Invoke(FooImpl, Bar): 61811 ms
Direct MethodInfo.Invoke(IFoo, Bar): 37078 ms
Virtual (Func<int>)Expression.Compile(): 2894 ms
Direct (Func<int>)Expression.Compile(): 2242 ms
Virtual (Func<IFoo, int>)Expression.Compile(): 2319 ms
Direct (Func<FooImpl, int>)Expression.Compile(): 2051 ms
Virtual (Func<IFoo, int>)Expression.CompileToMethod(): 996 ms
Direct (Func<FooImpl, int>)Expression.CompileToMethod(): 679 ms
Virtual () => IFoo.Bar(): 796 ms
Direct () => FooImpl.Bar(): 469 ms
Virtual IFoo.Bar(): 531 ms
Direct Foo.Bar(): 68 ms
J'espère que cela t'aides.
On peut diviser une question en 2 cas:
- comment le travail .NET nu avec la méthode s'appelle elle-même (question d'infrastructure)?
- comment les optimiseurs aident-ils à appeler la méthode?
ExpressionTest.exe en mode Release avec optimisation (paramètres de version par défaut). NET 4.5.2:
Compiled Virtual Call: 4625 ms
Compiled Direct Call: 3361 ms
Lambda Virtual Call: 1096 ms
Lambda Direct Call: 576 ms
Virtual Call: 649 ms
Direct Call: 144 ms
Nous voyons que "Appel direct" en 4,5 fois plus rapide que "Appel virtuel". Mais comme nous le voyons ci-dessus, ce n'est pas du tout un appel. La méthode des barres a été intégrée.
ExpressionTest.exe en mode Release sans optimisation .NET 4.5.2 :
Compiled Virtual Call: 5394 ms
Compiled Direct Call: 4666 ms
Lambda Virtual Call: 1800 ms
Lambda Direct Call: 1683 ms
Virtual Call: 1154 ms
Direct Call: 1112 ms
Ainsi, "Appel direct" est environ 3-4% plus rapide que "Appel virtuel".
Question similaire: Performance de l'appel virtuel "direct" par rapport à l'appel d'interface en C #
Astuce: en mode de libération, aucun appel n'est effectué dans le cas "Appel direct". CPU allant de 00B531BC (mov eax ...) à 00B531C8 (jl 00B531BC) uniquement.
for (int i = 0; i < iterationCount; i++)
00B531BA xor edx,edx
foo.Bar();
00B531BC mov eax,dword ptr [ebx+4] // actual loop begin
00B531BF cmp byte ptr [eax],al
for (int i = 0; i < iterationCount; i++)
00B531C1 inc edx
00B531C2 cmp edx,0BEBC200h // 0BEBC200h = 200000000
00B531C8 jl 00B531BC // loop begin address