This is the fifth in a series of video tutorials on how to use the PerfView profiling tool. It is best to watch the video using one of the high quality links on the right so the text is readable. This tutoral is on PerfView's 'Drill Into' feature, which allows you to selectively ungroup a set of samples in isolation, so you can understand just that part in more detail. You may wish to also to to the first tutorial on data collection or the second tutoral on data analysis if you have not already done so.
The PerfView tool is a free Windows performance tool developed by the Microsoft .NET Runtime Performance team for investigating both managed can unmanaged performance problems. If you are having a performance problem, especially if it is a .NET application, it is hard to overestimate the value of this tool.
You can get the PerfView tool (for free) at the Microsoft Download center. (bing search on 'PerfView download'). PerfView consists of a single XCOPYable EXE so it is easy to simply 'try out'. You can literally open the .ZIP file, and double click on the .EXE inside to launch it and then follow along with the video tutorial. Ultimately you will want to copy this file out of the ZIP file (e.g. drag it to the desktop) to make it easier to launch.