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I got an email today on an issue that I think is pretty common when you try to memory leak analysis on a dump with debug diag . They had set up a leak rule in debug diag to monitor for leaks and then ran the memory analysis on it to see what was leaking and the results looked something like this:   Warning mscorwks.dll is responsible for 372.46 MBytes worth of outstanding allocations. The following are the top 2 memory consuming functions: mscorwks!EEVirtualAlloc+119 : 312.00 MBytes worth of outstanding allocations. mscorwks!EEHeapAlloc+142 : 60.46 MBytes worth of outstanding allocations. If this is unexpected, please contact the vendor of this module, Microsoft Corporation , for further assistance with this issue. So what does this mean...

I was out looking for some sample scripts for tinyget and ran across this ANTS Memory Profiler review where Scott Seely has tested it out on some of my debugging labs . I haven’t had the time and/or opportunity to test it out myself but since many people have asked me if I had used it or what I thought of it I thought I’d just point you to someone who has instead:) Have fun, Tess Read More...

Is it a plane, is it a bird, is it a UFO? Before you can delve into any kind of troubleshooting of an issue you need to thoroughly define it.  If you don’t you’ll probably end up spending a lot of time randomly gathering and looking at data that is probably not even relevant to the issue at hand.  More importantly, how do you even know that your problem is fixed if you don’t have a good definition of the problem? This might sound like common sense, but having worked with troubleshooting the better part of the last 10 years I can tell you that it is extremely common that people start looking at data before really understanding the problem.  More often than not this is because people are stressed and want to fix the problem fast...

I came back from a long vacation today and I’ve finally caught up with enough emails to do something useful with my day. As I scanned through my blog email bucket I noticed that I had a lot of emails relating to my last post on dumping .net exceptions in windbg , and most of them asked why they see OutOfMemoryExceptions on the heap, and how to troubleshoot this. I think I have mentioned this before, but it seems like it is worth mentioning again as it is probably buried deep in some post from way back when… When you dump out all the exceptions on your .net GC heap (using !dumpheap -type Exception for example) these 3 types of exceptions will always show up, independently of what type of .net process you are debugging. 79330c30       ...

Yesterday I found this really nice Channel 9 interview with Maoni Stephens (Dev Owner of the CLR GC) and Andrew Pardoe (Program manager for the CLR GC) where they talked about the new Background GC in CLR 4.0. She also talks about it here and there is not much value in me repeating what she already says there but basically the main points of the video and the post are: Concurrent GC is being replaced by Background GC in CLR 4.0 Concurrent GC is the mode of the GC that you use in desktop applications for example.  The goal of the concurrent GC is to minimize pause time, and it does so by allowing you to still allocate while a GC is in progress (hence the concurrent part). Concurrent GC is only available in workstation mode.  In server...

I have put together a quick and dirty debug diag script for troubleshooting .net memory leaks. (attached to this post) The reason I put it together was mainly to show how you can create your own debug diag scripts but feel free to use it to troubleshoot memory leaks, knowing that it does string parsing on the output so it is a bit prone to errors if sos changes output formats. NOTE: This script will only work on .NET 2.0 x86 memory dumps Mourad recently published a whitepaper on debug diag that talks about how to use it for various scenarios and he also explains how to create some basic scripts and I used this as my starting point. My script loads up sos from the framework directory and goes through the following steps. 1. Print .NET Framework...

A colleague of mine, John Allen, created an awesome tool way back that displays memory usage in a process very nicely. I use screenshots from it from time to time in presentations or posts but unfortunately that tool is not publicly available. Since lots of people have asked me about it I figured I would just do a quick and dirty mock-up (based on the same ideas) and post the VS solution here. This sample tool will give you a visual overview of the virtual memory space (from a memory dump), show you where your allocations exist and what types of allocations you have. For example in the screenshot below you can see that at the beginning of the memory space we have a lot of virtual allocations (dark green – committed, light green - reserved),...

A few weeks back me and Micke (one of our Architect Evangelists) had a session at TechDays where we talked about “things that looked good on paper” i.e. things that sound pretty ok in the design/development phase but sometimes turn out to be a disaster in production. We are both pretty passionate about making the lives of the ops. people easier by thinking about the maintenance of the sites/apps at design time, rather than having it be an afterthought.  I stole the title of this post from one of Mickes talks about bridging the gap between dev and ops.  The topics we brought up are based on issues that we commonly see in prod. environments and we started off each section with a quote and dissected the pros and cons and what we think...

Yesterday I had a nice chat with Richard and Carl at .NET Rocks . We talked about .net, debugging, memory issues and a bunch of other stuff, and in the end I got a pop quiz that I failed:) See if you can figure out what caused the outage on their servers… The show will be uploaded here some time today. Laters, Tess Read More...

I get several emails every week through the blog asking for help on various issues.  Unfortunately due to time constraints I can’t really look at them all on an individual bases but I thought this particular request might be interesting to share. The problem description was “One of our w3wp.exe’s just keep on growing (slowly), and never releasing memory back to the pot.  The main offender appears to be System.String and System.Object[]”  and the email then had some !dumpheap –stat output (from windbg and sos) 0:000> .load sos 0:000> !dumpheap -stat ... 654060a8     5622       292344 System.Data.SqlClient.SqlBuffer 79109778     5505      ...