I am new to Vtune, but I've used statistical profilers in the past, as well as profilers like gprof.
I have written a DLL that serves as a "plug-in" to other applications. I don't have source to the applications it runs under. If I create a VTune project and sample the application, how do I see function calls for the DLL?
You do not need to have source code of the application in order to get sampled functions displayed in the Sampling View. If the application is built with preserving debug info, you will get even the applications functions names. If not, you will have the sampling results against DLLs functions only, whereas the executables functions will be exposed as virtual addresses of function entries.
If youre interested in measuring the number of your functions calls, you will need to run Call Graph. Without debug info in the application executable, youll get your DLLs entries only, but for the DLL performance analysis it could be enough.
Do not forget to compile your DLL with debug info: use /DEBUG and /Zi or ZI options.