I have written a C# program having some thousand lines and several threads. Execution works fine for several hours/days until the application, which is running on a Windows server, starts to slow everything (other programs/web server) down as it suddenly begins to use up about 50-80% of the CPU.
I assume that it is stuck in some while-loop, but I do not know where exactly. It would already be a help to know which thread uses up the largest share of the system resources. As there is not any exception thrown, I do not see any direct possibility to find out.
The code has already been inspected but I did not find any significant/obvious programming mistakes.
Does anybody know a good way to let Visual Studio monitor the current CPU-load in order to show where it is used up?
Oh, how I love Managed Stack Explorer. http://mse.codeplex.com/ for most versions of .NET and https://github.com/vadimskipin/MSE for 4.0
Point it at your running application, and it snapshots the stacks of each thread. After looking at a few snapshots, you'll work out where the problem is. Oh, the nastiness of the problem I was facing when I first learnt of this. Oh the joy when it let me find what I'd been hunting for days in just a few minutes.
You can use Perfview (http://www.microsoft.com/en-us/download/details.aspx?id=28567) to capture and the analyse ETL traces when this happens.
Related
So this is a weird one.
I created a WPF application using MahApps for the GUI. So far my testing indicates that the app works fine on several different machines. Of course this is not the case on the client's machine.
The client makes use of Terminal Services and Windows Server 2008R2. Several users can be logged into their own version of the server at anytime. The app starts up fine once or twice, but after a day or so, it no longer opens up.
The app doesn't show up in the Application tab of Task Manager, but its process can be seen to be running in Processes Tab of Task Manager.
To be honest, I'm completely stumped. I had a look at the event manager log and couldn't find anything indicative of a problem. (Of course I might have missed something). I saw another SO question suggesting to disable hardware acceleration, but I'm not if that would help.
Any and all ideas would be greatly appreciated.
EDIT:
I thought I might mention the only thing that helps is if we restart the client machine.
EDIT:
I think I have isolated the issue to integration with Twain (should probably have mentioned that as another possible factor). I think the Twain library (unmanaged code) somehow stalls without sending back an error. Disabling it has "fixed" the issue.
This somehow relates to Twain and multi-session setups. I'm almost sure of it.
First you can analyze the wait chain in Windows Resource Monitor to check if there are any resources the process is waiting for. (You can find more information about the wait chain here or here.)
If you don't find any viable suspects there, you can create a memory dump of the hanging process and analyze the call stacks. If you don't know how to create one, you can read about it here. If you want to use Windows Task Manager and your OS is 64-bit then please be aware that you need to use the same bitness of Task Manager as the application.
That is: If your application is 64-bit then you have to use C:\Windows\System32\taskmgr.exe and if it's 32-bit you have to use C:\Windows\SysWOW64\taskmgr.exe. If you forget this important step you'll just get an unusable dump full of gibberish.
After you got the memory dump you can either load it into WinDbg (using the same bitness as the application) or Visual Studio (best to use 2015 or later) and analyze the call stacks of all running threads.
You can download WinDbg here and read about the necessary WinDbg configuration here. For the list of all threads you need to use this SOS command.
If you need help in loading memory dumps into Visual Studio you can find more information here.
After you've looked at the call stacks you most definitely find the answer what is waiting on what resources and is thus preventing the shutdown or startup of the application. It can either be a classic deadlock or an external resource like writing/reading of a file or some other waiting without a timeout like accessing a database or an URL that can't be reached at the moment. And of course it can also be just an infinite loop - if it doesn't consume much CPU then perhaps with some kind of DoEvents in between.
And last but very not least: If you are really interested what can be analyzed if an application hangs you can read about an example analysis done by the absolutely awesome great Mark Russinovich here.
The application uses Xamarin.Android, which may be a big problem in itself. The problem is that sometimes it just quits (process is being terminated) and there's nothing in the log that can be associated with it. (although I guess that it's related to running out of memory, but I can't yet prove it — according to DDMS, most of the times all is OK, and if Xamarin.Android uses another pool of memory, then I don't know how to measure it)
I've searched the code base for "Environment.Exit" and, of course, didn't found anything.
What are the options for finding the culprit of such thing?
You could try to use the garbage collector by yourself. Just run
Runtime.getRuntime().gc();
The Runtime instance has also a method to read the free memory space. So you could figure out by yourself whether it's a memory problem.
EDIT:
Oh I read that Xamarin uses the C# language. But I'm quite sure that C# has similar methods.
When you say log, are you referring to an application log, or the device log?
When tracking down these sorts of bugs, I've always found aLogCat invaluable.
I open it, clear all the current logs, then use my application up to the point where it crashes. Then I quickly go back to aLogCat, pause it and scroll up to where the error is - it's usually found in the nearest red/orange blocks.
There's a blog post here about how I found attributes left out by the Xamarin linker using this method.
I have a large-ish Winforms application written in C# which is periodically unresponsive. The issue seems to occur once the application has been use for an hour or so. Exact timings are difficult to gather as users often go off to work on something selse, get back to it and find it has become unresponsive.
I think a memory leak can be ruled out as I'm not seeing excessive memory usage (I've asked users to send a screenshot of the task manager and memory usagage is the same as I would see when the application is runnning normally)
Similarly, CPU usage is normal (single digit %)
As I've so far been unable to recreate the issue on mydevelopment PC I am planning on sitting next to one of the affected users and mirror every action the user performs in order to recreate this. (I'll be setting up a laptop to RDP in to my main PC)
Recreating the issue is one thing, but I'll need to find out what is actually going on in the application.
Could anyone tell me if running in debug mode (through visual studio) will be sufficient or will I need to do something different?
I've searched through a few posts and I've seen mention of profiling software, however I'm not sure if this would only help with general performance issues or memory management issues.
Alternatively, if anyone has come across similar freezing issues then do you have any suggestions of the kind of causes for this?
Some technical details: Aplication is C#, compiled against .NET 3.5, winforms GUI. There are a few external libraries (most significant is ComponentFactory Krypton Suite). Data access is to a Microsoft SQL Server 2005 database. The solution contains 39 projects, I'm not sure if that might have something to do with it?
Any suggestions/pointers would be greatly appreciated.
The application is working much more reliably now, freezing issues still occur on occasion but nowhere near as often as before.
The issue appears to be related to the endpoint security (in this case, Cisco Security Agent) present in the environment I'm working in, application has been whitelisted and has has significantly rediced the instances of application hangs. The development system I work on does not have this endpoint security present, so it didn't show up in early stages of testing.
Thanks for all your feedback, I think there are still threading and garbage collection issues that need cleaning up, hopefully this should sort out the last few issues.
On some machines my C# app crashes when started. How to find out what is the cause of the problem? Where to start my research?
When I get managed exceptions I have nice StackTrace and exception messages so I have good start point. But in AppCrash dialog there are some weird hex numbers, I don't know what they mean.
P.S. This machines do have appropriate .NET Framework installed.
Update: I'm not talking about specific exceptions, but rather about what are common methods of fixing those. I want to learn how to do it myself and not asking on forums about every error I encounter.
I would look in the event viewer before starting looking at memory dumps etc. Many times it can be Graphic Cards drivers etc who causes the crash and the event viewer will then show what have happen.
I would suggest taking a look at windbg to analyze the crash dump.
See this article for details:
http://msdn.microsoft.com/en-us/windows/hardware/gg463009.aspx
At a blind guess I'd say you don't have the correct version of the .NET framework on the machine that is failing. Eg, you are trying to run a .net4 application on a machine where .net2 only is installed.
How about posting a screenshot/text of the error?
Have you tried windbg with crashdump option ?.
so something like adplus –crash –sc c:\myfolder\Myapp.exe
You can find more details here http://blogs.msdn.com/b/anandbms/archive/2005/04/20/410225.aspx.
we have a dotnet 2.0 desktop winforms app and it seems to randomly crash. no stack trace, vent log, or anything. it just dissapears.
There are a few theories:
machine simply runs out of resources. some people have said you will always get a window handle exception or a gdi exception but others say it might simply cause crashes.
we are using wrappers around non managed code for 2 modules. exceptions inside either of these modules could cause this behavior.
again, this is not reproducible so i wanted to see if there were any suggestions on how to debug better or anything i can put on the machine to "catch" the crash before it happens to help us understand whats going on.
Your best bet is to purchase John Robbins' book "Debugging Microsoft .NET 2.0 Applications". Your question can go WAY deeper than we have room to type here.
Sounds for me like you need to log at first - maybe you can attach with PostSharp a logger to your methods (see Log4PostSharp) . This will certainly slow you down a lot and produce tons of messages. But you should be able to narrow the problematic code down ... Attach there more logs - remove others. Maybe you can stress-test this parts, later. If the suspect parts are small enough you might even do a code review there.
I know, your question was about debugging - but this could be an approach, too.
You could use Process Monitor from SysInternals (now a part of Microsoft) filtered down to just what you want to monitor. This would give you a good place to start. Just start with a tight focus or make sure you have plenty of space for the log file.
I agree with Boydski. But I also offer this suggestion. Take a close look at the threads if you're doing multi-threading. I had an error like this once that took a long long time to figure out and actually ended up with John Robbins on the phone helping out with it. It turned out to be improper exception handling with threads.
Run your app, with pdb files, and attach WinDbg, make run.
Whem crash occur WinDbg stop app.
Execute this command to generate dump file :
.dump /ma c:\myapp.dmp
An auxiliary tool of analysis is ADPlus
Or try this :
Capturing user dumps using Performance alert
How to use ADPlus to troubleshoot "hangs" and "crashes"
Debugging on the Windows Platform
Do you have a try/catch block around the line 'Application.Run' call that starts the GUI thread? If not do add one and put some logging in for any exceptions thrown there.
You can also wrie up the Application.ThreadException event and log that in case that gives you some more hints.
you should use a global exception handler:
http://msdn.microsoft.com/en-us/library/system.windows.forms.application.threadexception.aspx
I my past I have this kind of behaviour primarily in relation to COM objects not being released and/or threading issues. Dive into the suggestions that you have gotten here already, but I would also suggest to look into whether you properly release the non-managed objects, so that they do not leak memory.