37

I'm trying to improve the performance of our application. We have a lot of Activator.CreateInstance calls that are causing some grief.

We instantiate a lot of classes based on an interface (ITabDocument) and after looking around I thought of using this code:

The code is no better (infact marginally slower) than using the Activator.CreateInstance code we had.

    public static Func<T> CreateInstance<T>(Type objType) where T : class, new()
    {
        var dynMethod = new DynamicMethod("DM$OBJ_FACTORY_" + objType.Name, objType, null, objType);
        ILGenerator ilGen = dynMethod.GetILGenerator();
        ilGen.Emit(OpCodes.Newobj, objType.GetConstructor(Type.EmptyTypes));
        ilGen.Emit(OpCodes.Ret);
        return (Func<T>)dynMethod.CreateDelegate(typeof(Func<T>));
    }

I'm wondering why this is, all I'm doing is:

ITabDocument document = CreateInstance<ITabDocument>(Type.GetType("[Company].Something"));

Is there a better way of creating objects which would assist with the above? Its a little hard when you're not sure of the concrete type.

4

6 回答 6

54

我在这些之间做了一些基准测试（我会写下最基本的细节）：

public static T Instance() //~1800 ms
{
    return new T();
}

public static T Instance() //~1800 ms
{
    return new Activator.CreateInstance<T>();
}

public static readonly Func<T> Instance = () => new T(); //~1800 ms

public static readonly Func<T> Instance = () => 
                                 Activator.CreateInstance<T>(); //~1800 ms

//works for types with no default constructor as well
public static readonly Func<T> Instance = () => 
               (T)FormatterServices.GetUninitializedObject(typeof(T)); //~2000 ms


public static readonly Func<T> Instance = 
     Expression.Lambda<Func<T>>(Expression.New(typeof(T))).Compile();  
     //~50 ms for classes and ~100 ms for structs

正如 CD 所说，编译表达式是最快的，而且幅度很大。除具有默认构造函数的类型外，所有方法均有效。(T)FormatterServices.GetUninitializedObject(typeof(T))

当每个泛型类型都有一个静态类时，缓存编译的结果委托是微不足道的。喜欢：

public static class New<T> where T : new()
{
    public static readonly Func<T> Instance = Expression.Lambda<Func<T>>
                                              (
                                               Expression.New(typeof(T))
                                              ).Compile();
}

注意new约束。调用任何东西

MyType me = New<MyType>.Instance();

除了第一次将类加载到内存中之外，执行速度将是最快的。

为了有一个使用默认构造函数和不使用默认构造函数处理两种类型的类，我采用了一种混合方法，从这里开始：

public static class New<T>
{
    public static readonly Func<T> Instance = Creator();

    static Func<T> Creator()
    {
        Type t = typeof(T);
        if (t == typeof(string))
            return Expression.Lambda<Func<T>>(Expression.Constant(string.Empty)).Compile();

        if (t.HasDefaultConstructor())
            return Expression.Lambda<Func<T>>(Expression.New(t)).Compile();

        return () => (T)FormatterServices.GetUninitializedObject(t);
    }
}

public static bool HasDefaultConstructor(this Type t)
{
    return t.IsValueType || t.GetConstructor(Type.EmptyTypes) != null;
}

也会以有效的方式处理值类型。

请注意，(T)FormatterServices.GetUninitializedObject(t)对于string. 因此，对字符串进行了特殊处理以返回空字符串。

于 2013-04-23T06:52:50.760 回答
22

这可能会有所帮助：不要使用 Activator.CreateInstance 或 ConstructorInfo.Invoke，使用已编译的 lambda 表达式：

// Make a NewExpression that calls the ctor with the args we just created
NewExpression newExp = Expression.New(ctor, argsExp);                  

// Create a lambda with the New expression as body and our param object[] as arg
LambdaExpression lambda = Expression.Lambda(typeof(ObjectActivator), newExp, param);            


// Compile it
ObjectActivator compiled = (ObjectActivator)lambda.Compile();
于 2011-07-05T12:00:14.250 回答
9

问题是，如果您要直接一遍又一遍地调用 CreateInstance 而不是将结果保存在某处并一遍又一遍地使用该结果，您可能应该继续并在其中缓存。

internal static class DelegateStore<T> {
     internal static IDictionary<string, Func<T>> Store = new ConcurrentDictionary<string,Func<T>>();
}

public static T CreateInstance<T>(Type objType) where T : class
{
    Func<T> returnFunc;
    if(!DelegateStore<T>.Store.TryGetValue(objType.FullName, out returnFunc)) {
        var dynMethod = new DynamicMethod("DM$OBJ_FACTORY_" + objType.Name, objType, null, objType);
        ILGenerator ilGen = dynMethod.GetILGenerator();
        ilGen.Emit(OpCodes.Newobj, objType.GetConstructor(Type.EmptyTypes));
        ilGen.Emit(OpCodes.Ret);
        returnFunc = (Func<T>)dynMethod.CreateDelegate(typeof(Func<T>));
        DelegateStore<T>.Store[objType.FullName] = returnFunc;
    }
    return returnFunc();
}
于 2011-07-11T13:28:08.857 回答
7

2019 年 12 月 13 日，
nawfal 的答案基准化

以 NetCore3.1 为基准，只是看到这仍然是多么必要。

[MemoryDiagnoser, ThreadingDiagnoser]
[SimpleJob(runtimeMoniker: RuntimeMoniker.NetCoreApp31)]
[GenericTypeArguments(typeof(TestClass))]
public class ActivatorBenchmark<T> where T : new()
{
    [Benchmark(Baseline = true)]
    [Arguments(1_000)]
    [Arguments(1_000_000)]
    [Arguments(100_000_000)]

    public void ActivatorTest1(int x)
    {
        for (int i = 0; i < x; i++)
        {
            var t = new T();
        }
    }

    [Benchmark]
    [Arguments(1_000)]
    [Arguments(1_000_000)]
    [Arguments(100_000_000)]
    public void ActivatorTest2(int x)
    {
        for (int i = 0; i < x; i++)
        {
            var t = New<T>.Instance();
        }
    }
}

public class TestClass
{
    public string Name { get; set; }
    public int Id { get; set; }
    public string Email { get; set; }
}

public static class TestHelpers
{
    public static class New<T>
    {
        public static readonly Func<T> Instance = Creator();

        private static Func<T> Creator()
        {
            Type t = typeof(T);
            if (t == typeof(string))
                return Expression.Lambda<Func<T>>(Expression.Constant(string.Empty)).Compile();

            if (t.HasDefaultConstructor())
                return Expression.Lambda<Func<T>>(Expression.New(t)).Compile();

            return () => (T)FormatterServices.GetUninitializedObject(t);
        }
    }

    public static bool HasDefaultConstructor(this Type t)
    {
        return t.IsValueType || t.GetConstructor(Type.EmptyTypes) != null;
    }
}

.

// * Detailed results *
ActivatorBenchmark<TestClass>.ActivatorTest1: Job-RRTXQH(Runtime=.NET Core 3.1) [x=1000]
Runtime = .NET Core 3.1.0 (CoreCLR 4.700.19.56402, CoreFX 4.700.19.56404), X64 RyuJIT; GC = Concurrent Workstation
Mean = 30.9925 us, StdErr = 0.1962 us (0.63%); N = 17, StdDev = 0.8088 us
Min = 30.2190 us, Q1 = 30.4151 us, Median = 30.4745 us, Q3 = 31.5188 us, Max = 32.7203 us
IQR = 1.1037 us, LowerFence = 28.7595 us, UpperFence = 33.1744 us
ConfidenceInterval = [30.2049 us; 31.7802 us] (CI 99.9%), Margin = 0.7876 us (2.54% of Mean)
Skewness = 0.96, Kurtosis = 2.4, MValue = 2
-------------------- Histogram --------------------
[29.944 us ; 30.909 us) | @@@@@@@@@@@
[30.909 us ; 31.555 us) | @@
[31.555 us ; 32.301 us) | @@
[32.301 us ; 32.996 us) | @@
---------------------------------------------------

ActivatorBenchmark<TestClass>.ActivatorTest2: Job-RRTXQH(Runtime=.NET Core 3.1) [x=1000]
Runtime = .NET Core 3.1.0 (CoreCLR 4.700.19.56402, CoreFX 4.700.19.56404), X64 RyuJIT; GC = Concurrent Workstation
Mean = 7.0534 us, StdErr = 0.0144 us (0.20%); N = 14, StdDev = 0.0538 us
Min = 6.9228 us, Q1 = 7.0269 us, Median = 7.0687 us, Q3 = 7.0849 us, Max = 7.1367 us
IQR = 0.0580 us, LowerFence = 6.9399 us, UpperFence = 7.1718 us
ConfidenceInterval = [6.9927 us; 7.1142 us] (CI 99.9%), Margin = 0.0607 us (0.86% of Mean)
Skewness = -0.76, Kurtosis = 3.12, MValue = 2
-------------------- Histogram --------------------
[6.903 us ; 7.148 us) | @@@@@@@@@@@@@@
---------------------------------------------------

ActivatorBenchmark<TestClass>.ActivatorTest1: Job-RRTXQH(Runtime=.NET Core 3.1) [x=1000000]
Runtime = .NET Core 3.1.0 (CoreCLR 4.700.19.56402, CoreFX 4.700.19.56404), X64 RyuJIT; GC = Concurrent Workstation
Mean = 27.6912 ms, StdErr = 0.0412 ms (0.15%); N = 13, StdDev = 0.1486 ms
Min = 27.5318 ms, Q1 = 27.6171 ms, Median = 27.6435 ms, Q3 = 27.7196 ms, Max = 28.0946 ms
IQR = 0.1025 ms, LowerFence = 27.4633 ms, UpperFence = 27.8734 ms
ConfidenceInterval = [27.5132 ms; 27.8691 ms] (CI 99.9%), Margin = 0.1780 ms (0.64% of Mean)
Skewness = 1.56, Kurtosis = 4.57, MValue = 2
-------------------- Histogram --------------------
[27.477 ms ; 28.150 ms) | @@@@@@@@@@@@@
---------------------------------------------------

ActivatorBenchmark<TestClass>.ActivatorTest2: Job-RRTXQH(Runtime=.NET Core 3.1) [x=1000000]
Runtime = .NET Core 3.1.0 (CoreCLR 4.700.19.56402, CoreFX 4.700.19.56404), X64 RyuJIT; GC = Concurrent Workstation
Mean = 7.0697 ms, StdErr = 0.0239 ms (0.34%); N = 15, StdDev = 0.0927 ms
Min = 6.9195 ms, Q1 = 6.9889 ms, Median = 7.0681 ms, Q3 = 7.1187 ms, Max = 7.2497 ms
IQR = 0.1298 ms, LowerFence = 6.7942 ms, UpperFence = 7.3134 ms
ConfidenceInterval = [6.9706 ms; 7.1687 ms] (CI 99.9%), Margin = 0.0991 ms (1.40% of Mean)
Skewness = 0.22, Kurtosis = 2.08, MValue = 2
-------------------- Histogram --------------------
[6.887 ms ; 7.252 ms) | @@@@@@@@@@@@@@@
---------------------------------------------------

ActivatorBenchmark<TestClass>.ActivatorTest1: Job-RRTXQH(Runtime=.NET Core 3.1) [x=100000000]
Runtime = .NET Core 3.1.0 (CoreCLR 4.700.19.56402, CoreFX 4.700.19.56404), X64 RyuJIT; GC = Concurrent Workstation
Mean = 2.7852 s, StdErr = 0.0093 s (0.33%); N = 15, StdDev = 0.0358 s
Min = 2.7426 s, Q1 = 2.7576 s, Median = 2.7693 s, Q3 = 2.8141 s, Max = 2.8629 s
IQR = 0.0565 s, LowerFence = 2.6728 s, UpperFence = 2.8989 s
ConfidenceInterval = [2.7469 s; 2.8235 s] (CI 99.9%), Margin = 0.0383 s (1.38% of Mean)
Skewness = 0.76, Kurtosis = 2.21, MValue = 2
-------------------- Histogram --------------------
[2.735 s ; 2.796 s) | @@@@@@@@@@
[2.796 s ; 2.876 s) | @@@@@
---------------------------------------------------

ActivatorBenchmark<TestClass>.ActivatorTest2: Job-RRTXQH(Runtime=.NET Core 3.1) [x=100000000]
Runtime = .NET Core 3.1.0 (CoreCLR 4.700.19.56402, CoreFX 4.700.19.56404), X64 RyuJIT; GC = Concurrent Workstation
Mean = 698.4029 ms, StdErr = 1.3760 ms (0.20%); N = 15, StdDev = 5.3292 ms
Min = 688.2649 ms, Q1 = 693.8483 ms, Median = 697.9546 ms, Q3 = 703.2100 ms, Max = 707.1939 ms
IQR = 9.3617 ms, LowerFence = 679.8057 ms, UpperFence = 717.2526 ms
ConfidenceInterval = [692.7056 ms; 704.1001 ms] (CI 99.9%), Margin = 5.6972 ms (0.82% of Mean)
Skewness = 0.09, Kurtosis = 2.08, MValue = 2
-------------------- Histogram --------------------
[686.374 ms ; 709.085 ms) | @@@@@@@@@@@@@@@
---------------------------------------------------

// * Summary *

BenchmarkDotNet=v0.12.0, OS=Windows 10.0.18362
Intel Core i9-9980HK CPU 2.40GHz, 1 CPU, 16 logical and 8 physical cores
.NET Core SDK=3.1.100
  [Host]     : .NET Core 3.1.0 (CoreCLR 4.700.19.56402, CoreFX 4.700.19.56404), X64 RyuJIT
  Job-RRTXQH : .NET Core 3.1.0 (CoreCLR 4.700.19.56402, CoreFX 4.700.19.56404), X64 RyuJIT

Runtime=.NET Core 3.1

|         Method |         x |             Mean |          Error |         StdDev | Ratio | Completed Work Items | Lock Contentions |       Gen 0 |     Gen 1 | Gen 2 |    Allocated |
|--------------- |---------- |-----------------:|---------------:|---------------:|------:|---------------------:|-----------------:|------------:|----------:|------:|-------------:|
| ActivatorTest1 |      1000 |        30.993 us |      0.7876 us |      0.8088 us |  1.00 |               0.0001 |                - |      4.7607 |         - |     - |     39.06 KB |
| ActivatorTest2 |      1000 |         7.053 us |      0.0607 us |      0.0538 us |  0.23 |               0.0000 |                - |      4.7760 |         - |     - |     39.06 KB |
|                |           |                  |                |                |       |                      |                  |             |           |       |              |
| ActivatorTest1 |   1000000 |    27,691.175 us |    177.9530 us |    148.5988 us |  1.00 |               0.0625 |                - |   4781.2500 |         - |     - |  39064.19 KB |
| ActivatorTest2 |   1000000 |     7,069.695 us |     99.0538 us |     92.6550 us |  0.26 |               0.0156 |                - |   4781.2500 |         - |     - |   39062.5 KB |
|                |           |                  |                |                |       |                      |                  |             |           |       |              |
| ActivatorTest1 | 100000000 | 2,785,181.093 us | 38,325.0183 us | 35,849.2459 us |  1.00 |               2.0000 |                - | 478000.0000 | 2000.0000 |     - | 3906418.4 KB |
| ActivatorTest2 | 100000000 |   698,402.860 us |  5,697.2360 us |  5,329.1981 us |  0.25 |               2.0000 |                - | 478000.0000 |         - |     - |   3906250 KB |

// * Hints *
Outliers
  ActivatorBenchmark<TestClass>.ActivatorTest2: Runtime=.NET Core 3.1 -> 1 outlier  was  removed, 2 outliers were detected (6.92 us, 9.73 us)
  ActivatorBenchmark<TestClass>.ActivatorTest1: Runtime=.NET Core 3.1 -> 2 outliers were removed (28.56 ms, 29.78 ms)

// * Legends *
  x                    : Value of the 'x' parameter
  Mean                 : Arithmetic mean of all measurements
  Error                : Half of 99.9% confidence interval
  StdDev               : Standard deviation of all measurements
  Ratio                : Mean of the ratio distribution ([Current]/[Baseline])
  Completed Work Items : The number of work items that have been processed in ThreadPool (per single operation)
  Lock Contentions     : The number of times there was contention upon trying to take a Monitor's lock (per single operation)
  Gen 0                : GC Generation 0 collects per 1000 operations
  Gen 1                : GC Generation 1 collects per 1000 operations
  Gen 2                : GC Generation 2 collects per 1000 operations
  Allocated            : Allocated memory per single operation (managed only, inclusive, 1KB = 1024B)
  1 us                 : 1 Microsecond (0.000001 sec)

// * Diagnostic Output - ThreadingDiagnoser *

// * Diagnostic Output - MemoryDiagnoser *
于 2019-12-14T01:30:05.440 回答
3

您可能会从生成相同代码中获得一些开销。

为ILGenerator工厂动态创建代码。

创建某种映射或Dictionary您已经使用过的类型，并保留为该类型创建的工厂方法。

于 2011-07-05T12:05:25.790 回答
0

构造委托的通用方法，直接调用构造函数。使用给定委托类型的签名自动搜索给定类型的构造函数并构造该类型的委托。代码在这里：

/// <summary>
/// Reflective object construction helper.
/// All methods are thread safe.
/// </summary>
public static class Constructor
{
    /// <summary>
    /// Searches an instanceType constructor with delegateType-matching signature and constructs delegate of delegateType creating new instance of instanceType.
    /// Instance is casted to delegateTypes's return type. 
    /// Delegate's return type must be assignable from instanceType.
    /// </summary>
    /// <param name="delegateType">Type of delegate, with constructor-corresponding signature to be constructed.</param>
    /// <param name="instanceType">Type of instance to be constructed.</param>
    /// <returns>Delegate of delegateType wich constructs instance of instanceType by calling corresponding instanceType constructor.</returns>
    public static Delegate Compile(Type delegateType,Type instanceType)
    {
        if (!typeof(Delegate).IsAssignableFrom(delegateType))
        {
            throw new ArgumentException(String.Format("{0} is not a Delegate type.",delegateType.FullName),"delegateType");
        }
        var invoke = delegateType.GetMethod("Invoke");
        var parameterTypes = invoke.GetParameters().Select(pi => pi.ParameterType).ToArray();
        var resultType = invoke.ReturnType;
        if(!resultType.IsAssignableFrom(instanceType))
        {
            throw new ArgumentException(String.Format("Delegate's return type ({0}) is not assignable from {1}.",resultType.FullName,instanceType.FullName));
        }
        var ctor = instanceType.GetConstructor(
            BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic, null, parameterTypes, null);
        if(ctor == null)
        {
            throw new ArgumentException("Can't find constructor with delegate's signature","instanceType");
        }
        var parapeters = parameterTypes.Select(Expression.Parameter).ToArray();

        var newExpression = Expression.Lambda(delegateType,
            Expression.Convert(Expression.New(ctor, parapeters), resultType),
            parapeters);
        var @delegate = newExpression.Compile();
        return @delegate;
    }
    public static TDelegate Compile<TDelegate>(Type instanceType)
    {
        return (TDelegate) (object) Compile(typeof (TDelegate), instanceType);
    }
}

是Yappi项目来源的一部分。使用它，您可以构造委托调用给定类型的任何构造函数，包括带参数的构造函数（ref 和 out 参数除外）。

示例用法：

var newList = Constructor.Compile<Func<int, IList<String>>>(typeof (List<String>));
var list = newList(100);

构建委托后，将其存储在静态字典或具有通用参数的类的静态字段中。不要每次都构造新的委托。使用一个委托来构造给定类型的多个实例。

于 2011-07-30T11:41:59.960 回答