什么可以“固定” Silverlight 内存中的对象？
我正在调试一个似乎疯狂泄漏内存的应用程序；大部分似乎是由于固定对象的碎片（在 WriteableBitmap 中下载的图像数据）造成的。但是，我并不是故意使用 GC.Handle 或类似的东西。我所做的就是将数据存储在 MemoryStream 中，并像这样引用它。
哪些操作将数据固定在内存中，但没有明确说明？另外，我如何使用 WinDbg 找到固定它的内容？
编辑：根据请求，这里是与一大块空闲内存相邻的 System.Int32 数组上的 !GCRoot 之一的（稍微清理过的）输出。这代表了所有大的空闲块。
编辑 2： 在与我的新朋友 WinDbg 和 SOS 相处之后，我发现 WriteableBitmaps 和 MemoryStream 对象都是“固定”的，并且应仔细分配以防止内存碎片。阅读已接受答案中的文章，了解为什么需要这样做的解释。
DOMAIN(1AC72358):HANDLE(Pinned):72c12f8:Root: 174c5e20(System.Object[])->
16533060(Project.ProjectParts.PartContainer)->
167fe554(Project.ProjectParts.Part.PartActivity)->
167d21d8(Project.ProjectParts.Sprites.Graphic)->
16770f28(System.Windows.Controls.Canvas)->
16770e1c(System.Windows.Controls.Canvas)->
16770ee4(System.Collections.Generic.Dictionary`2[[MS.Internal.IManagedPeerBase, System.Windows],[System.Object, mscorlib]])->
1680e778(System.Collections.Generic.Dictionary`2+Entry[[MS.Internal.IManagedPeerBase, System.Windows],[System.Object, mscorlib]][])->
16770f9c(System.Windows.Controls.Canvas)->
16819114(System.Collections.Generic.Dictionary`2[[MS.Internal.IManagedPeerBase, System.Windows],[System.Object, mscorlib]])->
16819160(System.Collections.Generic.Dictionary`2+Entry[[MS.Internal.IManagedPeerBase, System.Windows],[System.Object, mscorlib]][])->
16818df4(System.Windows.Controls.Canvas)->
16818e58(System.Collections.Generic.Dictionary`2[[MS.Internal.IManagedPeerBase, System.Windows],[System.Object, mscorlib]])->
16819f10(System.Collections.Generic.Dictionary`2+Entry[[MS.Internal.IManagedPeerBase, System.Windows],[System.Object, mscorlib]][])->
168194c4(System.Windows.Controls.Canvas)->
16819528(System.Collections.Generic.Dictionary`2[[MS.Internal.IManagedPeerBase, System.Windows],[System.Object, mscorlib]])->
16819574(System.Collections.Generic.Dictionary`2+Entry[[MS.Internal.IManagedPeerBase, System.Windows],[System.Object, mscorlib]][])->
16819370(System.Windows.Controls.Image)->
21c82138(System.Collections.Generic.Dictionary`2[[MS.Internal.IManagedPeerBase, System.Windows],[System.Object, mscorlib]])->
21c82184(System.Collections.Generic.Dictionary`2+Entry[[MS.Internal.IManagedPeerBase, System.Windows],[System.Object, mscorlib]][])->
168195dc(System.Windows.Media.Imaging.WriteableBitmap)->
21c7ce2c(System.Int32[])
DOMAIN(1AC72358):HANDLE(AsyncPinned):72c1dfc:Root: 166bae48(System.Threading.OverlappedData)->
1654d448(System.Threading.IOCompletionCallback)->
1654c29c(System.Net.Sockets.SocketAsyncEventArgs)->
1654bad4(System.Net.Sockets.Socket+StaticConnectAsyncState)->
1654ba40(System.Net.Sockets.SocketAsyncEventArgs)->
1654b684(System.ServiceModel.Channels.SocketConnectionInitiator+ConnectAsyncResult)->
1654b414(System.ServiceModel.Channels.ConnectionPoolHelper+EstablishConnectionAsyncResult)->
1654b3b0(System.ServiceModel.Channels.ClientFramingDuplexSessionChannel+OpenAsyncResult)->
1654b380(System.ServiceModel.Channels.CommunicationObject+OpenAsyncResult)->
1654b330(System.ServiceModel.Channels.CommunicationObject+OpenAsyncResult)->
1654b0f4(System.ServiceModel.Channels.ServiceChannel+SendAsyncResult)->
1654b070(System.ServiceModel.ClientBase`1+AsyncOperationContext[[Cassandra.Common.WCF.IAsyncWcfRequestProcessor, Cassandra.Common.Silverlight]])->
1654b05c(System.ComponentModel.AsyncOperation)->
1654b04c(Project.Common.IoC.InvokeAsyncCompletedEventRequestsArgs)->
1654afec(System.Action`1[[Project.Common.IoC.ProcessRequestsAsyncCompletedArgsEx, Project.Common.SL]])->
1654afc8(Project.Common.IoC.AsyncRequestDispatcherEx+<>c__DisplayClass1)->
1654afa0(Project.Common.IoC.NetResponseReceiver)->
1653408c(System.Action`2[[Cassandra.Common.ExceptionInfo, Cassandra.Common.Silverlight],[Cassandra.Common.ExceptionType, Cassandra.Common.Silverlight]])->
16533ffc(Project.ProjectParts.ILE.Services.EngineProxyService+<>c__DisplayClass5)->
16533fdc(System.Action`1[[Cassandra.Common.ReceivedResponses, Cassandra.Common.Silverlight]])->
16533fbc(Project.ProjectParts.ILE.Services.IEngineProxyExtensions+<>c__DisplayClass1`2[[Project.Services.RequestsAndResponses.ListMediaServersByTokenRequest, Project.Services.RequestsAndResponses.Silverlight],[Project.Services.RequestsAndResponses.ListInstitutionMediaServersResponse, Project.Services.RequestsAndResponses.Silverlight]])->
16533f9c(System.Action`1[[Project.Services.RequestsAndResponses.ListInstitutionMediaServersResponse, Project.Services.RequestsAndResponses.Silverlight]])->
1650a2a0(Project.ProjectParts.ILE.MainPage)->
1674ea0c(Project.ProjectParts.ActivityTimer)->
165330a4(Project.ProjectParts.PauseManager)->
165330bc(System.Collections.Generic.List`1[[Project.ProjectParts.IPausable, ActivityFramework]])->
166a8610(System.Object[])->
167ca858(Project.ProjectParts.ActivityTimer)->
167ca838(Project.ProjectParts.ActivityTimerEventHandler)->
16533060(Project.ProjectParts.PartContainer)->
167fe554(Project.ProjectParts.Part.PartActivity)->
167d21d8(Project.ProjectParts.Sprites.Graphic)->
16770f28(System.Windows.Controls.Canvas)->
16770e1c(System.Windows.Controls.Canvas)->
16770ee4(System.Collections.Generic.Dictionary`2[[MS.Internal.IManagedPeerBase, System.Windows],[System.Object, mscorlib]])->
1680e778(System.Collections.Generic.Dictionary`2+Entry[[MS.Internal.IManagedPeerBase, System.Windows],[System.Object, mscorlib]][])->
16770f9c(System.Windows.Controls.Canvas)->
16819114(System.Collections.Generic.Dictionary`2[[MS.Internal.IManagedPeerBase, System.Windows],[System.Object, mscorlib]])->
16819160(System.Collections.Generic.Dictionary`2+Entry[[MS.Internal.IManagedPeerBase, System.Windows],[System.Object, mscorlib]][])->
16818df4(System.Windows.Controls.Canvas)->
16818e58(System.Collections.Generic.Dictionary`2[[MS.Internal.IManagedPeerBase, System.Windows],[System.Object, mscorlib]])->
16819f10(System.Collections.Generic.Dictionary`2+Entry[[MS.Internal.IManagedPeerBase, System.Windows],[System.Object, mscorlib]][])->
168194c4(System.Windows.Controls.Canvas)->
16819528(System.Collections.Generic.Dictionary`2[[MS.Internal.IManagedPeerBase, System.Windows],[System.Object, mscorlib]])->
16819574(System.Collections.Generic.Dictionary`2+Entry[[MS.Internal.IManagedPeerBase, System.Windows],[System.Object, mscorlib]][])->
16819370(System.Windows.Controls.Image)->
21c82138(System.Collections.Generic.Dictionary`2[[MS.Internal.IManagedPeerBase, System.Windows],[System.Object, mscorlib]])->
21c82184(System.Collections.Generic.Dictionary`2+Entry[[MS.Internal.IManagedPeerBase, System.Windows],[System.Object, mscorlib]][])->
168195dc(System.Windows.Media.Imaging.WriteableBitmap)->
21c7ce2c(System.Int32[])
DOMAIN(1AC72358):HANDLE(Pinned):72c2b18:Root: 21c7ce2c(System.Int32[])
I am working on debugging an application that seems to leak memory like crazy; most of it seems due to fragmentation from pinned objects(downloaded image data in a WriteableBitmap). However, I am not intentionally using GC.Handle or anything like it. All I do is store the data in a MemoryStream, and reference it like that.
What operations pin data in memory, that don't explicitly say so? Also, how can I find what pinned it using WinDbg?
EDIT: Per request, here is a (slightly sanitized) output of one of a !GCRoot on a System.Int32 array adjacent to a large block of free memory. This is representative of all of the large free blocks.
EDIT 2: After spending time with my new friends WinDbg and SOS, I found that WriteableBitmaps AND MemoryStream objects, are both 'pinned', and should be allocated carefully to prevent memory fragmentation. Read the article from the accepted answer for an explanation as to why that needs to be done.
DOMAIN(1AC72358):HANDLE(Pinned):72c12f8:Root: 174c5e20(System.Object[])->
16533060(Project.ProjectParts.PartContainer)->
167fe554(Project.ProjectParts.Part.PartActivity)->
167d21d8(Project.ProjectParts.Sprites.Graphic)->
16770f28(System.Windows.Controls.Canvas)->
16770e1c(System.Windows.Controls.Canvas)->
16770ee4(System.Collections.Generic.Dictionary`2[[MS.Internal.IManagedPeerBase, System.Windows],[System.Object, mscorlib]])->
1680e778(System.Collections.Generic.Dictionary`2+Entry[[MS.Internal.IManagedPeerBase, System.Windows],[System.Object, mscorlib]][])->
16770f9c(System.Windows.Controls.Canvas)->
16819114(System.Collections.Generic.Dictionary`2[[MS.Internal.IManagedPeerBase, System.Windows],[System.Object, mscorlib]])->
16819160(System.Collections.Generic.Dictionary`2+Entry[[MS.Internal.IManagedPeerBase, System.Windows],[System.Object, mscorlib]][])->
16818df4(System.Windows.Controls.Canvas)->
16818e58(System.Collections.Generic.Dictionary`2[[MS.Internal.IManagedPeerBase, System.Windows],[System.Object, mscorlib]])->
16819f10(System.Collections.Generic.Dictionary`2+Entry[[MS.Internal.IManagedPeerBase, System.Windows],[System.Object, mscorlib]][])->
168194c4(System.Windows.Controls.Canvas)->
16819528(System.Collections.Generic.Dictionary`2[[MS.Internal.IManagedPeerBase, System.Windows],[System.Object, mscorlib]])->
16819574(System.Collections.Generic.Dictionary`2+Entry[[MS.Internal.IManagedPeerBase, System.Windows],[System.Object, mscorlib]][])->
16819370(System.Windows.Controls.Image)->
21c82138(System.Collections.Generic.Dictionary`2[[MS.Internal.IManagedPeerBase, System.Windows],[System.Object, mscorlib]])->
21c82184(System.Collections.Generic.Dictionary`2+Entry[[MS.Internal.IManagedPeerBase, System.Windows],[System.Object, mscorlib]][])->
168195dc(System.Windows.Media.Imaging.WriteableBitmap)->
21c7ce2c(System.Int32[])
DOMAIN(1AC72358):HANDLE(AsyncPinned):72c1dfc:Root: 166bae48(System.Threading.OverlappedData)->
1654d448(System.Threading.IOCompletionCallback)->
1654c29c(System.Net.Sockets.SocketAsyncEventArgs)->
1654bad4(System.Net.Sockets.Socket+StaticConnectAsyncState)->
1654ba40(System.Net.Sockets.SocketAsyncEventArgs)->
1654b684(System.ServiceModel.Channels.SocketConnectionInitiator+ConnectAsyncResult)->
1654b414(System.ServiceModel.Channels.ConnectionPoolHelper+EstablishConnectionAsyncResult)->
1654b3b0(System.ServiceModel.Channels.ClientFramingDuplexSessionChannel+OpenAsyncResult)->
1654b380(System.ServiceModel.Channels.CommunicationObject+OpenAsyncResult)->
1654b330(System.ServiceModel.Channels.CommunicationObject+OpenAsyncResult)->
1654b0f4(System.ServiceModel.Channels.ServiceChannel+SendAsyncResult)->
1654b070(System.ServiceModel.ClientBase`1+AsyncOperationContext[[Cassandra.Common.WCF.IAsyncWcfRequestProcessor, Cassandra.Common.Silverlight]])->
1654b05c(System.ComponentModel.AsyncOperation)->
1654b04c(Project.Common.IoC.InvokeAsyncCompletedEventRequestsArgs)->
1654afec(System.Action`1[[Project.Common.IoC.ProcessRequestsAsyncCompletedArgsEx, Project.Common.SL]])->
1654afc8(Project.Common.IoC.AsyncRequestDispatcherEx+<>c__DisplayClass1)->
1654afa0(Project.Common.IoC.NetResponseReceiver)->
1653408c(System.Action`2[[Cassandra.Common.ExceptionInfo, Cassandra.Common.Silverlight],[Cassandra.Common.ExceptionType, Cassandra.Common.Silverlight]])->
16533ffc(Project.ProjectParts.ILE.Services.EngineProxyService+<>c__DisplayClass5)->
16533fdc(System.Action`1[[Cassandra.Common.ReceivedResponses, Cassandra.Common.Silverlight]])->
16533fbc(Project.ProjectParts.ILE.Services.IEngineProxyExtensions+<>c__DisplayClass1`2[[Project.Services.RequestsAndResponses.ListMediaServersByTokenRequest, Project.Services.RequestsAndResponses.Silverlight],[Project.Services.RequestsAndResponses.ListInstitutionMediaServersResponse, Project.Services.RequestsAndResponses.Silverlight]])->
16533f9c(System.Action`1[[Project.Services.RequestsAndResponses.ListInstitutionMediaServersResponse, Project.Services.RequestsAndResponses.Silverlight]])->
1650a2a0(Project.ProjectParts.ILE.MainPage)->
1674ea0c(Project.ProjectParts.ActivityTimer)->
165330a4(Project.ProjectParts.PauseManager)->
165330bc(System.Collections.Generic.List`1[[Project.ProjectParts.IPausable, ActivityFramework]])->
166a8610(System.Object[])->
167ca858(Project.ProjectParts.ActivityTimer)->
167ca838(Project.ProjectParts.ActivityTimerEventHandler)->
16533060(Project.ProjectParts.PartContainer)->
167fe554(Project.ProjectParts.Part.PartActivity)->
167d21d8(Project.ProjectParts.Sprites.Graphic)->
16770f28(System.Windows.Controls.Canvas)->
16770e1c(System.Windows.Controls.Canvas)->
16770ee4(System.Collections.Generic.Dictionary`2[[MS.Internal.IManagedPeerBase, System.Windows],[System.Object, mscorlib]])->
1680e778(System.Collections.Generic.Dictionary`2+Entry[[MS.Internal.IManagedPeerBase, System.Windows],[System.Object, mscorlib]][])->
16770f9c(System.Windows.Controls.Canvas)->
16819114(System.Collections.Generic.Dictionary`2[[MS.Internal.IManagedPeerBase, System.Windows],[System.Object, mscorlib]])->
16819160(System.Collections.Generic.Dictionary`2+Entry[[MS.Internal.IManagedPeerBase, System.Windows],[System.Object, mscorlib]][])->
16818df4(System.Windows.Controls.Canvas)->
16818e58(System.Collections.Generic.Dictionary`2[[MS.Internal.IManagedPeerBase, System.Windows],[System.Object, mscorlib]])->
16819f10(System.Collections.Generic.Dictionary`2+Entry[[MS.Internal.IManagedPeerBase, System.Windows],[System.Object, mscorlib]][])->
168194c4(System.Windows.Controls.Canvas)->
16819528(System.Collections.Generic.Dictionary`2[[MS.Internal.IManagedPeerBase, System.Windows],[System.Object, mscorlib]])->
16819574(System.Collections.Generic.Dictionary`2+Entry[[MS.Internal.IManagedPeerBase, System.Windows],[System.Object, mscorlib]][])->
16819370(System.Windows.Controls.Image)->
21c82138(System.Collections.Generic.Dictionary`2[[MS.Internal.IManagedPeerBase, System.Windows],[System.Object, mscorlib]])->
21c82184(System.Collections.Generic.Dictionary`2+Entry[[MS.Internal.IManagedPeerBase, System.Windows],[System.Object, mscorlib]][])->
168195dc(System.Windows.Media.Imaging.WriteableBitmap)->
21c7ce2c(System.Int32[])
DOMAIN(1AC72358):HANDLE(Pinned):72c2b18:Root: 21c7ce2c(System.Int32[])
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假设 silverlight 的工作方式与完整的 .net 框架相同，那么大小超过 85k 的对象几乎永远不会被垃圾收集。 http://msdn.microsoft.com/en-us/magazine/cc534993.aspx
我们将大型队列对象分解为一系列较小的队列，一旦它们缩小到正常运行大小，就可以收集数据结构。在此代码更改之前，一旦队列增长超过阈值，内存将永远不会被释放回操作系统。
这可能就是你正在经历的事情吗？
Assuming silverlight works in the same way as the full .net framework, an object over 85k in size will pretty much never be garbage collected. http://msdn.microsoft.com/en-us/magazine/cc534993.aspx
We broke up our large queue objects into an array of smaller queues which then allowed the data structure to be collected once they had shrunk back down to normal running size. Before this code change, once the queue had grown beyond the threshold the memory would never be released back to the OS.
Could this be what you are experiencing?
Pin 是在操作正在进行或处理程序引用存在时将控件中的异步或处理程序保持为“不重新定位在内存中”的机制。
在离开控件或视图模型或模型之前，您还应该检查是否有任何处理程序或异步操作，例如 WCF 客户端或 Http Web Service 客户端打开状态。如果退出控件、视图模型或模型时固定任何对象，则会出现内存泄漏。
另请记住，如果这些对象最终超过 85.000 字节，它们最终将处于第 2 代，在应用程序（域）终止之前不会进行垃圾收集。
如果对象小于 85K 并且在第 0 代的 GC 中幸存下来。它会提升到第 1 代，并且当存活或未释放或有东西持有它时，它将结束其生命到第 2 代，这在 SL 中不会被收集。
另请注意：如果频繁释放/分配这些对象将导致内存碎片。如果您的程序需要在内存中拥有连续的空间，并且由于碎片而没有那么大的空闲块，您将得到内存不足异常。
希望以上有帮助。
Pin is mechanism to hold Async or handlers in your controls to be "do not relocated in memory" while the operation is in progress or handler reference exists.
You should also check whether you have any handlers or Async operations such as WCF client or Http Web Service client open state, prior to leaving the control or view model or model. If any object is pinned when you exit the control, view model or model you will have memory leak for those.
Also keep in mind that if those object ends up to be more than 85.000bytes they end up to be in generation 2 which is not Garbage Collected until the application (domain) terminates.
If object is smaller than 85K and survives the GC for Generation 0. Its promoted to Generation 1, and when survive or is not released or something is holding its will be end its life to Generation 2, which in SL is not collected.
Also to note: if you release/allocate frequently those object will cause the memory to be fragmented. If your program requires to have continuous space in memory and there is no free block that big because of the fragmentation you will get out of memory exception.
Hope above helps.