Code:
/ DotNET / DotNET / 8.0 / untmp / whidbey / REDBITS / ndp / clr / src / BCL / System / GC.cs / 3 / GC.cs
// ==++== // // Copyright (c) Microsoft Corporation. All rights reserved. // // ==--== /*============================================================ ** ** Class: GC ** ** ** Purpose: Exposes features of the Garbage Collector through ** the class libraries. This is a class which cannot be ** instantiated. ** ** ===========================================================*/ namespace System { //This class only static members and doesn't require the serializable keyword. using System; using System.Security.Permissions; using System.Reflection; using System.Security; using System.Threading; using System.Runtime.CompilerServices; using System.Runtime.ConstrainedExecution; using System.Reflection.Cache; // !!!!!!!!!!!!!!!!!!!!!!! // make sure you change the def in vm\gc.h // if you change this! [Serializable] public enum GCCollectionMode { Default = 0, Forced = 1, Optimized = 2 } public static class GC { [MethodImplAttribute(MethodImplOptions.InternalCall)] internal static extern int nativeGetGCLatencyMode(); [MethodImplAttribute(MethodImplOptions.InternalCall)] internal static extern void nativeSetGCLatencyMode(int newLatencyMode); [MethodImplAttribute(MethodImplOptions.InternalCall)] private static extern int GetGenerationWR(IntPtr handle); [MethodImplAttribute(MethodImplOptions.InternalCall)] private static extern long nativeGetTotalMemory(); [MethodImplAttribute(MethodImplOptions.InternalCall)] private static extern void nativeCollectGeneration(int generation, int mode); [MethodImplAttribute(MethodImplOptions.InternalCall)] private static extern int nativeGetMaxGeneration(); [MethodImplAttribute(MethodImplOptions.InternalCall)] [ReliabilityContract(Consistency.WillNotCorruptState, Cer.Success)] private static extern int nativeCollectionCount (int generation); [MethodImplAttribute(MethodImplOptions.InternalCall)] internal static extern bool nativeIsServerGC(); [MethodImplAttribute(MethodImplOptions.InternalCall)] internal static extern void nativeAddMemoryPressure(UInt64 bytesAllocated); [MethodImplAttribute(MethodImplOptions.InternalCall)] internal static extern void nativeRemoveMemoryPressure(UInt64 bytesAllocated); [SecurityPermission(SecurityAction.LinkDemand, UnmanagedCode=true)] public static void AddMemoryPressure (long bytesAllocated) { if( bytesAllocated <= 0) { throw new ArgumentOutOfRangeException("bytesAllocated", Environment.GetResourceString("ArgumentOutOfRange_NeedPosNum")); } if( (4 == IntPtr.Size) && (bytesAllocated > Int32.MaxValue) ) { throw new ArgumentOutOfRangeException("pressure", Environment.GetResourceString("ArgumentOutOfRange_MustBeNonNegInt32")); } nativeAddMemoryPressure((ulong)bytesAllocated); } [SecurityPermission(SecurityAction.LinkDemand, UnmanagedCode=true)] public static void RemoveMemoryPressure (long bytesAllocated) { if( bytesAllocated <= 0) { throw new ArgumentOutOfRangeException("bytesAllocated", Environment.GetResourceString("ArgumentOutOfRange_NeedPosNum")); } if( (4 == IntPtr.Size) && (bytesAllocated > Int32.MaxValue) ) { throw new ArgumentOutOfRangeException("bytesAllocated", Environment.GetResourceString("ArgumentOutOfRange_MustBeNonNegInt32")); } nativeRemoveMemoryPressure((ulong) bytesAllocated); } // Returns the generation that obj is currently in. // [MethodImplAttribute(MethodImplOptions.InternalCall)] public static extern int GetGeneration(Object obj); // Forces a collection of all generations from 0 through Generation. // public static void Collect(int generation) { Collect(generation, GCCollectionMode.Default); } // Garbage Collect all generations. // public static void Collect() { //-1 says to GC all generations. nativeCollectGeneration(-1, (int)GCCollectionMode.Default); } public static void Collect(int generation, GCCollectionMode mode) { if (generation<0) { throw new ArgumentOutOfRangeException("generation", Environment.GetResourceString("ArgumentOutOfRange_GenericPositive")); } if ((mode < GCCollectionMode.Default) || (mode > GCCollectionMode.Optimized)) { throw new ArgumentOutOfRangeException(Environment.GetResourceString("ArgumentOutOfRange_Enum")); } nativeCollectGeneration(generation, (int)mode); } [ReliabilityContract(Consistency.WillNotCorruptState, Cer.Success)] public static int CollectionCount (int generation) { if (generation<0) { throw new ArgumentOutOfRangeException("generation", Environment.GetResourceString("ArgumentOutOfRange_GenericPositive")); } return nativeCollectionCount(generation); } // This method DOES NOT DO ANYTHING in and of itself. It's used to // prevent a finalizable object from losing any outstanding references // a touch too early. The JIT is very aggressive about keeping an // object's lifetime to as small a window as possible, to the point // where a 'this' pointer isn't considered live in an instance method // unless you read a value from the instance. So for finalizable // objects that store a handle or pointer and provide a finalizer that // cleans them up, this can cause subtle races with the finalizer // thread. This isn't just about handles - it can happen with just // about any finalizable resource. // // Users should insert a call to this method near the end of a // method where they must keep an object alive for the duration of that // method, up until this method is called. Here is an example: // // "...all you really need is one object with a Finalize method, and a // second object with a Close/Dispose/Done method. Such as the following // contrived example: // // class Foo { // Stream stream = ...; // protected void Finalize() { stream.Close(); } // void Problem() { stream.MethodThatSpansGCs(); } // static void Main() { new Foo().Problem(); } // } // // // In this code, Foo will be finalized in the middle of // stream.MethodThatSpansGCs, thus closing a stream still in use." // // If we insert a call to GC.KeepAlive(this) at the end of Problem(), then // Foo doesn't get finalized and the stream says open. [MethodImplAttribute(MethodImplOptions.InternalCall)] [ReliabilityContract(Consistency.WillNotCorruptState, Cer.Success)] public static extern void KeepAlive(Object obj); // Returns the generation in which wo currently resides. // public static int GetGeneration(WeakReference wo) { int result = GetGenerationWR(wo.m_handle); KeepAlive(wo); return result; } // Returns the maximum GC generation. Currently assumes only 1 heap. // public static int MaxGeneration { get { return nativeGetMaxGeneration(); } } [MethodImplAttribute(MethodImplOptions.InternalCall)] public static extern void WaitForPendingFinalizers(); // Indicates that the system should not call the Finalize() method on // an object that would normally require this call. // Has the DynamicSecurityMethodAttribute custom attribute to prevent // inlining of the caller. [MethodImplAttribute(MethodImplOptions.InternalCall)] [ReliabilityContract(Consistency.WillNotCorruptState, Cer.Success)] internal static extern void nativeSuppressFinalize(Object o); [ReliabilityContract(Consistency.WillNotCorruptState, Cer.Success)] public static void SuppressFinalize(Object obj) { if (obj == null) throw new ArgumentNullException("obj"); nativeSuppressFinalize(obj); } // Indicates that the system should call the Finalize() method on an object // for which SuppressFinalize has already been called. The other situation // where calling ReRegisterForFinalize is useful is inside a finalizer that // needs to resurrect itself or an object that it references. // Has the DynamicSecurityMethodAttribute custom attribute to prevent // inlining of the caller. [MethodImplAttribute(MethodImplOptions.InternalCall)] private static extern void nativeReRegisterForFinalize(Object o); public static void ReRegisterForFinalize(Object obj) { if (obj == null) throw new ArgumentNullException("obj"); nativeReRegisterForFinalize(obj); } // Returns the total number of bytes currently in use by live objects in // the GC heap. This does not return the total size of the GC heap, but // only the live objects in the GC heap. // public static long GetTotalMemory(bool forceFullCollection) { long size = nativeGetTotalMemory(); if (!forceFullCollection) return size; // If we force a full collection, we will run the finalizers on all // existing objects and do a collection until the value stabilizes. // The value is "stable" when either the value is within 5% of the // previous call to nativeGetTotalMemory, or if we have been sitting // here for more than x times (we don't want to loop forever here). int reps = 20; // Number of iterations long newSize = size; float diff; do { GC.WaitForPendingFinalizers(); GC.Collect(); size = newSize; newSize = nativeGetTotalMemory(); diff = ((float)(newSize - size)) / size; } while (reps-- > 0 && !(-.05 < diff && diff < .05)); return newSize; } [MethodImplAttribute(MethodImplOptions.InternalCall)] private static extern void SetCleanupCache(); private static ClearCacheHandler m_cacheHandler; private static readonly Object locker = new Object(); internal static event ClearCacheHandler ClearCache { add { lock (locker) { m_cacheHandler+=value; SetCleanupCache(); } } remove { lock (locker) m_cacheHandler-=value; } } //This method is called from native code. If you update the signature, please also update //mscorlib.h and COMUtilNative.cpp internal static void FireCacheEvent() { BCLDebug.Trace("CACHE", "Called FileCacheEvent"); ClearCacheHandler handler = Interlocked.Exchange(ref m_cacheHandler, null); if (handler!=null) { handler(null, null); } } } }
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