匿名函數gc分析

 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：

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：

　　

　　IL代碼也一摸同樣：

　　

　　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:

　　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gc

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：

　　

　　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。

　　附上類型定義的完整代碼，來龍去脈一目瞭然：

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.html

 

Vector3.Equals函數會有gc:

// 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(); }