CPU usage of w3wp rises to 100% on a ASP.NET MVC4 web application

问题:

We have a ASP.NET MVC4 application which uses Entity Framework 4.0. When we deploy on the production server, the CPU rises after some time (~2-5h) until nearly 100%. The memory also rises then until maximum. After a while the application pool will be resetted automatically because of the high memory.

Server: Windows 2008 R2 Standard SP1 IIS: 7 (V 7.5.7600.16385) Only one application pool and one webapplication is running.

Stacktrace from Debug Diagnostic Tool of the thread which consumes most of the CPU:

SNIReadSyncOverAsync(SNI_ConnWrapper*, SNI_Packet**, Int32)  .SNIReadSyncOverAsync(SNI_ConnWrapper*, SNI_Packet**, Int32)  System.Web.Hosting.UnsafeIISMethods.MgdIndicateCompletion(IntPtr, System.Web.RequestNotificationStatus ByRef)  System.Web.Hosting.UnsafeIISMethods.MgdIndicateCompletion(IntPtr, System.Web.RequestNotificationStatus ByRef)  ntdll!NtWaitForSingleObject  KERNELBASE!WaitForSingleObjectEx  System_Data!SNIReadSyncOverAsync  System_Data_ni!load_config_used  System_Data_ni!load_config_used  System_Data_ni!load_config_used  System_Data_ni!load_config_used  System_Data_ni!load_config_used  System_Data_ni!load_config_used  System_Data_ni!load_config_used  System_Data_ni!load_config_used  System_Data_ni!load_config_used  System_Data_ni!load_config_used  System_Data_ni!load_config_used  System_Data_ni!load_config_used  System_Data_ni!load_config_used  System_Data_ni!load_config_used  System_Data_ni!load_config_used  System_Data_Entity_ni  System_Data_Entity_ni  System_Data_Entity_ni  System_Data_Entity_ni  System_Core_ni  System_Core_ni  0x000007fe`99223112  0x000007fe`99222a88  0x000007fe`99222899  0x000007fe`992205cb  0x000007fe`99355596  System_Web_Mvc_ni+138058  System_Web_Mvc_ni+13ca67  System_Web_Mvc_ni+13e71c  System_Web_Mvc_ni+13ca03  System_Web_Mvc_ni+13d175  System_Web_Mvc_ni+13cbe9  System_Web_Mvc_ni+1431df  System_Web_Mvc_ni+13dade  System_Web_Mvc_ni+14f5fe  System_Web_Mvc_ni+13b0ef  System_Web_Mvc_ni+14f514  System_Web_ni  System_Web_ni  System_Web_ni  System_Web_ni  System_Web_ni  System_Web_ni  System_Web_ni  System_Web_ni  clr!UMThunkStub  webengine4!W3_MGD_HANDLER::ProcessNotification  webengine4!W3_MGD_HANDLER::DoWork  webengine4!RequestDoWork  webengine4!CMgdEngHttpModule::OnExecuteRequestHandler  iiscore!NOTIFICATION_CONTEXT::RequestDoWork  iiscore!NOTIFICATION_CONTEXT::CallModulesInternal  iiscore!NOTIFICATION_CONTEXT::CallModules  iiscore!W3_CONTEXT::DoWork  iiscore!W3_CONTEXT::IndicateCompletion  webengine4!MgdIndicateCompletion  System_Web_ni  System_Web_ni  System_Web_ni  System_Web_ni  clr!UM2MThunk_WrapperHelper  clr!UM2MThunk_Wrapper  clr!Thread::DoADCallBack  clr!UM2MDoADCallBack  clr!UMThunkStub  webengine4!W3_MGD_HANDLER::ProcessNotification  webengine4!ProcessNotificationCallback  clr!UnManagedPerAppDomainTPCount::DispatchWorkItem  clr!ThreadpoolMgr::ExecuteWorkRequest  clr!ThreadpoolMgr::WorkerThreadStart  clr!Thread::intermediateThreadProc  kernel32!BaseThreadInitThunk  ntdll!RtlUserThreadStart  

Have you an idea what is the reason of this CPU rising?

回答1:

Hey I had the exact same issue with SNIReadSyncOverAsync using a significant amount of thread time (I discovered this using DebugDiag).

I don't know if this will help anyone else but it looks like our problem was with the Azure DB server we were using. We had it set to only 50 DTUs, which has a maximum of 100 concurrent requests.

Basically SNIReadSyncOverAsync is so large because the web server has to sit there waiting for a response from the DB server, and the DB server can only handle 100 requests at a time so the web server ends up waiting for a long time (resulting in a 100% CPU usage and an inaccessible website). This can pop up with a recent increase in web traffic (e.g.: if you guys recently bought advertisements and saw your web traffic go up by a large percentage, now the 100 concurrent requests aren't enough)

So if you're like us and you're using Azure DB, check your DTU % usage. If its really high often (80-90%, etc.) try increasing it to double or even quadruple (this can be expensive!). We went from "Elastic Standard" (50 eDTUs) to "Standard S4" (400 DTUs) and we've yet to see the CPU usage hit 100%. In fact its been floating at around 7-9% since.

文章来源: CPU usage of w3wp rises to 100% on a ASP.NET MVC4 web application