匿名函數gc分析

時間 2019-12-05

標籤匿名函數分析欄目 Java 简体版

原文原文鏈接

測試一：使用member function建立action會產生gc，無論該函數是否訪問外部變量：html

    private System.Action memberAct = null;
    // gc 112B
    private void ActionWithMethod()
    {
        memberAct = new System.Action(LocalMethod);
    }
    // gc 112B, if LocalMethod() is static, then no gc
    private void ActionWithMethod2()
    {
        memberAct = LocalMethod;
    }
    // no gc
    private void ActionWithMethod3()
    {
        System.Action act = memberAct;
    }
    private void LocalMethod()
    {
        foreach (var item in lst)
            Debug.Log(item);
    }

　　ActionWithMethod和ActionWithMethod2是等效的，gc值以下所示：緩存

　　IL代碼也一摸同樣：函數

　　因此將一個member function複製給一個action會產生gc，解決的辦法就是ActionWithMethod3，也就是用一個actin member緩存起來，而後將緩存的action member複製給新建的action，這樣只會產生一次gc:測試

　　若是將LocalMethod設置爲static函數，則ActionWithMethod2也不會產生gc:

    private static void LocalMethod()
    {
    }

測試二：使用匿名函數，若是訪問了外部變量，也會產生gc；若是不訪問外部變量，則只產生一次gcthis

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
public class TestAnonymousFunctionGC : MonoBehaviour
{
    private System.Action actMember = null;
    private int iMember = 1;
    public TestAnonymousFunctionGC()
    {
    }
    private void Update()
    {
        UnityEngine.Profiling.Profiler.BeginSample("*** AnoymousFunctionWithoutArg ***");
        AnoymousFunctionWithoutArg();
        UnityEngine.Profiling.Profiler.EndSample();

        UnityEngine.Profiling.Profiler.BeginSample("*** AnoymousFunctionWithMemberArg ***");
        AnoymousFunctionWithMemberArg();
        UnityEngine.Profiling.Profiler.EndSample();

        UnityEngine.Profiling.Profiler.BeginSample("*** AnoymousFunctionWithLocalArg1 ***");
        AnoymousFunctionWithLocalArg1();
        UnityEngine.Profiling.Profiler.EndSample();

        UnityEngine.Profiling.Profiler.BeginSample("*** AnoymousFunctionWithLocalArg2 ***");
        AnoymousFunctionWithLocalArg2();
        UnityEngine.Profiling.Profiler.EndSample();

        UnityEngine.Profiling.Profiler.BeginSample("*** AnoymousFunctionWithLocalArg3 ***");
        AnoymousFunctionWithLocalArg3();
        UnityEngine.Profiling.Profiler.EndSample();
    }
    // no gc
    private void AnoymousFunctionWithoutArg()
    {
        actMember = () => { };
    }
    // gc 112B
    private void AnoymousFunctionWithMemberArg()
    {
        actMember = () =>
        {
            Debug.Log(iMember);
        };
    }
    // gc 129B
    private void AnoymousFunctionWithLocalArg1()
    {
        bool bValue = true;
        actMember = () =>
        {
            Debug.Log(bValue);
        };
    }
    // gc 132B
    private void AnoymousFunctionWithLocalArg2()
    {
        int iValue = 100;
        actMember = () =>
        {
            Debug.Log(iValue);
        };
    }
    // gc 136B
    private void AnoymousFunctionWithLocalArg3()
    {
        int iValue = 1;
        int iValue2 = 2;
        actMember = () =>
        {
            Debug.Log(iValue);
            Debug.Log(iValue2);
        };
    }
}

　　同時還能夠發現，匿名函數引用的外部變量的個數會影響gc的值，爲何呢？來分析一波：spa

　　能夠看到訪問外部變量的匿名函數，會致使 臨時對象的建立，這樣會致使gc，那位爲何每一個臨時變量的gc值不同呢，咱們來看一下這些臨時class的定義：

　　能夠看匿名函數所訪問的外部變量都會在臨時類裏面建立一個拷貝，這樣每一個類對象的大小就不同了。3d

　　附上類型定義的完整代碼，來龍去脈一目瞭然：code

public class TestAnonymousFunctionGC : MonoBehaviour
{
    // Fields
    private Action actMember;
    private int iMember;

    // Methods
    public TestAnonymousFunctionGC()
    {
        this.actMember = null;
        this.iMember = 1;
        base..ctor();
        return;
    }

    [CompilerGenerated]
    private void <AnoymousFunctionWithMemberArg>b__5_0()
    {
        Debug.Log((int) this.iMember);
        return;
    }

    private void AnoymousFunctionWithLocalArg1()
    {
        <>c__DisplayClass6_0 class_;
        class_ = new <>c__DisplayClass6_0();
        class_.bValue = 1;
        this.actMember = new Action(class_.<AnoymousFunctionWithLocalArg1>b__0);
        return;
    }

    private void AnoymousFunctionWithLocalArg2()
    {
        <>c__DisplayClass7_0 class_;
        class_ = new <>c__DisplayClass7_0();
        class_.iValue = 100;
        this.actMember = new Action(class_.<AnoymousFunctionWithLocalArg2>b__0);
        return;
    }

    private void AnoymousFunctionWithLocalArg3()
    {
        <>c__DisplayClass8_0 class_;
        class_ = new <>c__DisplayClass8_0();
        class_.iValue = 1;
        class_.iValue2 = 2;
        this.actMember = new Action(class_.<AnoymousFunctionWithLocalArg3>b__0);
        return;
    }

    private void AnoymousFunctionWithMemberArg()
    {
        this.actMember = new Action(this.<AnoymousFunctionWithMemberArg>b__5_0);
        return;
    }

    private void AnoymousFunctionWithoutArg()
    {
        this.actMember = (<>c.<>9__4_0 != null) ? <>c.<>9__4_0 : (<>c.<>9__4_0 = new Action(this.<AnoymousFunctionWithoutArg>b__4_0));
        return;
    }

    private void Update()
    {
        Profiler.BeginSample("*** AnoymousFunctionWithoutArg ***");
        this.AnoymousFunctionWithoutArg();
        Profiler.EndSample();
        Profiler.BeginSample("*** AnoymousFunctionWithMemberArg ***");
        this.AnoymousFunctionWithMemberArg();
        Profiler.EndSample();
        Profiler.BeginSample("*** AnoymousFunctionWithLocalArg1 ***");
        this.AnoymousFunctionWithLocalArg1();
        Profiler.EndSample();
        Profiler.BeginSample("*** AnoymousFunctionWithLocalArg2 ***");
        this.AnoymousFunctionWithLocalArg2();
        Profiler.EndSample();
        Profiler.BeginSample("*** AnoymousFunctionWithLocalArg3 ***");
        this.AnoymousFunctionWithLocalArg3();
        Profiler.EndSample();
        return;
    }

    // Nested Types
    [Serializable, CompilerGenerated]
    private sealed class <>c
    {
        // Fields
        public static readonly TestAnonymousFunctionGC.<>c <>9;
        public static Action <>9__4_0;

        // Methods
        static <>c()
        {
            <>9 = new TestAnonymousFunctionGC.<>c();
            return;
        }

        public <>c()
        {
            base..ctor();
            return;
        }

        internal void <AnoymousFunctionWithoutArg>b__4_0()
        {
            return;
        }
    }

    [CompilerGenerated]
    private sealed class <>c__DisplayClass6_0
    {
        // Fields
        public bool bValue;

        // Methods
        public <>c__DisplayClass6_0()
        {
            base..ctor();
            return;
        }

        internal void <AnoymousFunctionWithLocalArg1>b__0()
        {
            Debug.Log((bool) this.bValue);
            return;
        }
    }

    [CompilerGenerated]
    private sealed class <>c__DisplayClass7_0
    {
        // Fields
        public int iValue;

        // Methods
        public <>c__DisplayClass7_0()
        {
            base..ctor();
            return;
        }

        internal void <AnoymousFunctionWithLocalArg2>b__0()
        {
            Debug.Log((int) this.iValue);
            return;
        }
    }

    [CompilerGenerated]
    private sealed class <>c__DisplayClass8_0
    {
        // Fields
        public int iValue;
        public int iValue2;

        // Methods
        public <>c__DisplayClass8_0()
        {
            base..ctor();
            return;
        }

        internal void <AnoymousFunctionWithLocalArg3>b__0()
        {
            Debug.Log((int) this.iValue);
            Debug.Log((int) this.iValue2);
            return;
        }
    }
}

 
Collapse Methods

參考：https://blog.uwa4d.com/archives/Anonymous_heapmemory.htmlhtm

Vector3.Equals函數會有gc:對象

        // Vector3.Equeals有GC 28B
        {
            UnityEngine.Profiling.Profiler.BeginSample("*** Vector3.Equals ***");
            Vector3 dir1 = Vector3.one, dir2 = Vector3.one;
            var equals = dir1.Equals(dir2);
            UnityEngine.Profiling.Profiler.EndSample();
        }

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