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我正在通过使用 Windbg 分析内存转储来调查一个运行高达 10gb 内存的 web 应用程序。

这是 !dumpheap -stat 输出的底部：

00007ff9545df5d0   166523     13321840 System.Runtime.Caching.MemoryCache
00007ff9545df4a0   166523     14654024 System.Runtime.Caching.CacheMemoryMonitor
00007ff9545de990   166523     14654024 System.Runtime.Caching.SRef[]
00007ff9545dcef0   166523     14654024 System.Runtime.Caching.GCHandleRef`1[[System.Runtime.Caching.MemoryCacheStore, System.Runtime.Caching]][]
00007ff9545dfb28   166523     19982760 System.Runtime.Caching.MemoryCacheStatistics
00007ff956778510   333059     21315680 System.Int64[]
00007ff95679c988    41597     31250111 System.Byte[]
00007ff9545e08c8  1332184     31972416 System.Runtime.Caching.MemoryCacheEqualityComparer
00007ff9545dfe48  1332184     31972416 System.Runtime.Caching.SRef
00007ff956780ff0  1332200     31972800 System.SizedReference
00007ff956724620  1498777     35970648 System.Threading.TimerHolder
00007ff95677fb30  1536170     36868080 System.Runtime.Remoting.Messaging.CallContextSecurityData
00007ff956796f28  1606960     38567040 System.Object
00007ff9545df810  1332184     42629888 System.Runtime.Caching.GCHandleRef`1[[System.Runtime.Caching.MemoryCacheStore, System.Runtime.Caching]]
00007ff9545dda38  1332184     42629888 System.Runtime.Caching.UsageBucket[]
00007ff9567ae930  1332268     42632576 Microsoft.Win32.SafeHandles.SafeWaitHandle
00007ff9545df968  1498707     47958624 System.Runtime.Caching.GCHandleRef`1[[System.Threading.Timer, mscorlib]]
00007ff9567adbf8  1498777     47960864 System.Threading.Timer
00007ff9545dff50  1332184     53287360 System.Runtime.Caching.CacheUsage
00007ff94986ead8  1536137     61445480 System.Web.Hosting.AspNetHostExecutionContextManager+AspNetHostExecutionContext
00007ff9567a2838  1332210     63946080 System.Threading.ManualResetEvent
00007ff956796948   293525     66384986 System.String
00007ff9545dfef0  1332184     74602304 System.Runtime.Caching.CacheExpires
00007ff9567add20  1498760     95920640 System.Threading.TimerCallback
00007ff9545dfa90  1332184    106574720 System.Runtime.Caching.MemoryCacheStore
00007ff95679b3b0  1333289    106663120 System.Collections.Hashtable
00007ff95678f138  1536171    110604312 System.Runtime.Remoting.Messaging.LogicalCallContext
00007ff9545dffb0  1332184    127889664 System.Runtime.Caching.UsageBucket
00007ff95679d1e0  1333292    128664768 System.Collections.Hashtable+bucket[]
00007ff9567245c0  1498777    131892376 System.Threading.TimerQueueTimer
00007ff9567aec48  1536255    135190440 System.Threading.ExecutionContext
00007ff9545dcf78  1332184    351696576 System.Runtime.Caching.ExpiresBucket[]
000000f82c79d9f0   473339    385303992      Free
00007ff956799220 40309535   1617342672 System.Int32[]
00007ff9545e0468 39965520   3836689920 System.Runtime.Caching.ExpiresBucket

所以有近 4000 万个实例System.Runtime.Caching.ExpiresBucket，总共使用了近 4GB 的内存。System.Runtime.Caching类出现在头号罪犯中相当多。

我随机抽取了一个System.Runtime.Caching.ExpiresBucket类的实例，并对其进行了 !gcroot 操作。产生 1 个线程需要很长时间（可能需要 30 分钟）......可能还有更多，但此时我中断了操作。

引用链超过 150 万行！但我可以在这里展示重要的部分：

0:000> !gcroot 000000f82dd4bc28
Thread 1964:
    000000fcbdbce6a0 00007ff8f9bbe388 Microsoft.AspNet.SignalR.SqlServer.ObservableDbOperation.ExecuteReaderWithUpdates(System.Action`2<System.Data.IDataRecord,Microsoft.AspNet.SignalR.SqlServer.DbOperation>)
        rbp-58: 000000fcbdbce6e8
            ->  000000fa2d1f26a0 Microsoft.AspNet.SignalR.SqlServer.ObservableDbOperation+<>c__DisplayClass1e
            ->  000000fa2d1f2110 Microsoft.AspNet.SignalR.SqlServer.ObservableDbOperation
            ->  000000fa2d1f24d0 System.Action
            ->  000000fa2d1f24a8 System.Object[]
            ->  000000fa2d1f2468 System.Action
            ->  000000fa2d1f1008 Microsoft.AspNet.SignalR.SqlServer.SqlReceiver
            ->  000000fa2d1f1330 System.Action
            ->  000000fa2d1f1308 System.Object[]
            ->  000000fa2d1f12c8 System.Action
            ->  000000fa2d1efb70 Microsoft.AspNet.SignalR.SqlServer.SqlStream
            ->  000000fa2d1f1528 System.Action
            ->  000000fa2d1f1500 System.Object[]
            ->  000000fa2d1f14c0 System.Action
            ->  000000fa2d1efb20 Microsoft.AspNet.SignalR.SqlServer.SqlMessageBus+<>c__DisplayClass3
            ->  000000f92d0b84e0 Microsoft.AspNet.SignalR.SqlServer.SqlMessageBus
            ->  000000f92d0b9568 System.Threading.Timer
            ->  000000f92d0b96d8 System.Threading.TimerHolder
            ->  000000f92d0b95a0 System.Threading.TimerQueueTimer
[... about 100 lines of the same TimerQueueTimer line above, but different memory addresses each time]
           ->  000000f92cf1be68 System.Threading.TimerQueueTimer
            ->  000000f92cf1be08 System.Threading.TimerCallback
            ->  000000f92cf1bb48 System.Web.RequestTimeoutManager
            ->  000000f92cf1bb80 System.Web.Util.DoubleLinkList[]
            ->  000000f92cf1bc00 System.Web.Util.DoubleLinkList
            ->  000000fb61323860 System.Web.RequestTimeoutManager+RequestTimeoutEntry
            ->  000000fb6131fd38 System.Web.HttpContext
            ->  000000fbe682a480 ASP.global_asax
            ->  000000fbe682ac00 System.Web.HttpModuleCollection
            ->  000000fbe682ac60 System.Collections.ArrayList
            ->  000000fbe682b598 System.Object[]
            ->  000000fbe682b018 System.Collections.Specialized.NameObjectCollectionBase+NameObjectEntry
            ->  000000fbe682b000 System.Web.Routing.UrlRoutingModule
            ->  000000faacec1f40 System.Web.Routing.RouteCollection
            ->  000000faacec2030 System.Collections.Generic.List`1[[System.Web.Routing.RouteBase, System.Web]]
            ->  000000fa2cfe4d80 System.Web.Routing.RouteBase[]
            ->  000000f9acf14cd8 System.Web.Http.WebHost.Routing.HttpWebRoute
            ->  000000f9acf149f8 System.Web.Http.Routing.RouteCollectionRoute
            ->  000000f9acf1f4f0 System.Web.Http.Routing.SubRouteCollection
            ->  000000f9acf1f510 System.Collections.Generic.List`1[[System.Web.Http.Routing.IHttpRoute, System.Web.Http]]
            ->  000000fa2cf8f310 System.Web.Http.Routing.IHttpRoute[]
            ->  000000fa2ceff770 System.Web.Http.Routing.HttpRoute
            ->  000000fa2ceff678 System.Web.Http.Routing.HttpRouteValueDictionary
            ->  000000fa2ceff6f0 System.Collections.Generic.Dictionary`2+Entry[[System.String, mscorlib],[System.Object, mscorlib]][]
            ->  000000fa2cef9e78 System.Web.Http.Controllers.HttpActionDescriptor[]
            ->  000000fa2cef7898 System.Web.Http.Controllers.ReflectedHttpActionDescriptor
            ->  000000f9aced4608 System.Web.Http.HttpConfiguration
            ->  000000f9aced4db0 System.Net.Http.Formatting.MediaTypeFormatterCollection
            ->  000000f9aced6f40 System.Collections.Generic.List`1[[System.Net.Http.Formatting.MediaTypeFormatter, System.Net.Http.Formatting]]
            ->  000000f9aced6f80 System.Net.Http.Formatting.MediaTypeFormatter[]
            ->  000000f9aced4df8 System.Net.Http.Formatting.JsonMediaTypeFormatter
            ->  000000f9acf1f448 System.Web.Http.Validation.ModelValidationRequiredMemberSelector
            ->  000000f9acf1f468 System.Collections.Generic.List`1[[System.Web.Http.Validation.ModelValidatorProvider, System.Web.Http]]
            ->  000000f9acf1f490 System.Web.Http.Validation.ModelValidatorProvider[]
            ->  000000f9acf1db40 Ninject.Web.WebApi.Validation.NinjectDefaultModelValidatorProvider
            ->  000000faaceca438 Ninject.StandardKernel
            ->  000000faaceca498 Ninject.Components.ComponentContainer
            ->  000000faaceca538 System.Collections.Generic.Dictionary`2[[System.Type, mscorlib],[Ninject.Components.INinjectComponent, Ninject]]
            ->  000000f9acece000 System.Collections.Generic.Dictionary`2+Entry[[System.Type, mscorlib],[Ninject.Components.INinjectComponent, Ninject]][]
            ->  000000f9acecdac8 Ninject.Activation.Caching.GarbageCollectionCachePruner
            ->  000000f9acecdcb8 System.Threading.Timer
            ->  000000f9acecdd30 System.Threading.TimerHolder
            ->  000000f9acecdcd8 System.Threading.TimerQueueTimer
[... just under 1.5 million lines of the same TimerQueueTimer line above, but different memory addresses each time]
            ->  000000f82dd4c028 System.Threading.TimerQueueTimer
            ->  000000f82dd4bfc8 System.Threading.TimerCallback
            ->  000000f82dd4ada0 System.Runtime.Caching.CacheExpires
            ->  000000f82dd4add8 System.Runtime.Caching.ExpiresBucket[]
            ->  000000f82dd4bc28 System.Runtime.Caching.ExpiresBucket

我在 !objsize 上运行000000f92d0b84e0 Microsoft.AspNet.SignalR.SqlServer.SqlMessageBus，但到目前为止它已经运行了大约 20 分钟，我期待一个非常高的数字。

是什么导致泄漏？SignalR 中是否存在使用背板的已知错误？我们使用的是 v2.0.2，我相信它不是最新的。但我没有在互联网上找到任何涉及 SignalR 和缓存的内存泄漏的文档。

编辑：

为了回答 Pawel 关于 SqlMessageBus 实例的问题，这里有更多 Windbg 输出：

0:000> !dumpheap -type SqlMessageBus
         Address               MT     Size
0000007ced6832a0 00007ff8f9edb708       24     
0000007ced6832b8 00007ff8f9a97da8       64     
0000007ced6832f8 00007ff8f9a97c90      248     
0000007ced685370 00007ff8f9edbc18       24     
0000007d6d917f48 00007ff8f9a97ec8       40     
0000007feda7c400 00007ff8f9e88b98       32     

Statistics:
              MT    Count    TotalSize Class Name
00007ff8f9edbc18        1           24 System.Lazy`1+Boxed[[Microsoft.AspNet.SignalR.SqlServer.SqlMessageBus, Microsoft.AspNet.SignalR.SqlServer]]
00007ff8f9edb708        1           24 System.Lazy`1+<>c[[Microsoft.AspNet.SignalR.SqlServer.SqlMessageBus, Microsoft.AspNet.SignalR.SqlServer]]
00007ff8f9e88b98        1           32 Microsoft.AspNet.SignalR.SqlServer.SqlMessageBus+<>c__DisplayClass3
00007ff8f9a97ec8        1           40 System.Lazy`1[[Microsoft.AspNet.SignalR.SqlServer.SqlMessageBus, Microsoft.AspNet.SignalR.SqlServer]]
00007ff8f9a97da8        1           64 System.Func`1[[Microsoft.AspNet.SignalR.SqlServer.SqlMessageBus, Microsoft.AspNet.SignalR.SqlServer]]
00007ff8f9a97c90        1          248 Microsoft.AspNet.SignalR.SqlServer.SqlMessageBus
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1 回答 1

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在我们的例子中，最终的原因是因为我们有一个类MemoryCache在其构造函数中创建了一个新的实例......我们应该将该类绑定为一个单例，但我们没有。所以基本上我们最终得到了数十万个MemoryCache实例。

于 2017-11-22T14:14:07.723 回答