My application seems to hang. What do I do? – Part 2

re: My application seems to hang. What do I do? – Part 2

Rudi — Thu, 23 Nov 2006 18:07:56 GMT

Hi,

I have been reading a lot on your blog (and others), but still there is something I cannot explain:

We have an ASP.NET application that can generate reports. However, some users will request soo much data that the server will throw an OutOfMemoryException.

We will fix the application so that users can not attempt to get that much data back.

But I still have the question why ASP.NET does not recover from the OutOfMemoryException. Initially we get the exception and after some more failed requests we will get the Server Application Unavailable error. My understanding is that since the request has been aborted, the memory used by the request should become 'unreachable' and the Garbage Collector should be capable of reclaiming the memory. But that does not seem to happen.

I have reviewed the code and none of the objects are set in Session/Application/Cache.

Would you have an explanation of why the memory is not being reclaimed?

New and Notable 127

Sam Gentile — Thu, 23 Nov 2006 18:11:56 GMT

I thought Thanksgiving morning is for adults to be sleeping in. Instead, not only are the kids up at

re: My application seems to hang. What do I do? – Part 2

maoni — Tue, 28 Nov 2006 02:50:32 GMT

Rudi, GC will attemp a collection before it returns OOM. When the server gives you unavailable error was it still getting OOM exceptions or due to something else?

re: My application seems to hang. What do I do? – Part 2

Nick Batell — Wed, 26 Dec 2007 10:59:17 GMT

Great post. Here is another article about the top 3 reasons <a href="http://www.correlsense.com/cto-blog/top-3-reasons-an-application-hangs/">applications hang</a> for no reason

re: My application seems to hang. What do I do? – Part 2

Ron Inbar — Sat, 05 Jul 2008 13:30:41 GMT

Hi Maoni,

My application seems to hang in the middle of GC.

The stack looks like this:

ntdll!NtWaitForSingleObject+0xa

kernel32!WaitForSingleObjectEx+0x130

mscorwks!Thread::LeaveRuntimeNoThrow+0xba

mscorwks!CLREvent::WaitEx+0x57

mscorwks!WKS::gc_heap::start_c_gc+0x1b

mscorwks!`string'+0x56f3a

mscorwks!WKS::GCHeap::GarbageCollectGeneration+0x17d

mscorwks!WKS::gc_heap::try_allocate_more_space+0x2f1

mscorwks!WKS::GCHeap::Alloc+0x6d

mscorwks!Alloc+0x7a

mscorwks!FastAllocatePrimitiveArray+0x71

mscorwks!JIT_NewArr1+0x43d

Base_ni!Philips.PmsCT.Base.MathLib.Vector3..ctor()+0x1c

The other threads all look more or less like this:

ntdll!NtWaitForSingleObject+0xa

kernel32!WaitForSingleObjectEx+0x130

mscorwks!Thread::LeaveRuntimeNoThrow+0xba

mscorwks!CLREvent::WaitEx+0x57

mscorwks!WKS::gc_heap::wait_for_gc_done+0x5b

mscorwks!WKS::GCHeap::WaitUntilGCComplete+0x4b

So the question is what is the GC waiting for?

Thanks,

Ron

re: My application seems to hang. What do I do? – Part 2

Ron Inbar — Sat, 05 Jul 2008 13:47:28 GMT

After submitting the previous post, I found out that there is one thread that doesn't have WKS::GCHeap::WaitUntilGCComplete on its stack. Its stack looks as follows:

ntdll!ZwWaitForMultipleObjects+0xa

kernel32!WaitForMultipleObjectsEx+0x1cf

mscorwks!WaitForMultipleObjectsEx_SO_TOLERANT+0xc1

mscorwks!Thread::DoAppropriateAptStateWait+0x41

mscorwks!Thread::DoAppropriateWaitWorker+0x195

mscorwks!Thread::DoAppropriateWait+0x5c

mscorwks!WaitHandleNative::CorWaitOneNative+0x19f

mscorlib_ni!System.Threading.WaitHandle.WaitOne(Int64, Boolean)+0x1f

Could it be that the GC is waiting for this thread to suspend, thereby creating a deadlock?

re: My application seems to hang. What do I do? – Part 2

maoni — Wed, 15 Oct 2008 02:08:43 GMT

Ron, both callstacks you showed are doing normal operations. The first one is waiting for the concurrent GC thread to wake it up and the second one is detecting that a GC is in progress and the threadpool suspended the thread.

New and Notable 127

Sam Gentile's Blog — Wed, 03 Dec 2008 21:20:46 GMT

I thought Thanksgiving morning is for adults to be sleeping in. Instead, not only are the kids up at the crack at dawn but one (the eight year old) is playing games on Vista and asking for Starbucks, while the nearly 4 year old is clamoring for princess