What is the Visual Studio Standard Collector process, and why does it use 10GB of RAM?

The Collector Process appears to be related to instrumentation/diagnostics of code running in debug mode, in Visual Studio 2015. Microsoft has acknowledged there is an issue with unbounded memory use of this process, and says,

We have researched the root cause and have made a fix that will be provided in VS2015 Update 1

So make sure you get the latest Visual Studio 2015 update. For mitigation in the meantime:

Meanwhile, if you notice that the process consumes too much memory you have two ways to recover. Simplest is just to restart your machine. That will get everything back to a fresh state. The other thing you can do to alleviate the memory consumption is to stop the Visual Studio Standard Collector Service using the Service Manager UI. The Name of the service is "VSStandardCollectorService140". It can be safely stopped when you not debugging with Visual Studio. If you stop the service while debugging (even stopped at a breakpoint) then the Diagnostic Tools window will display an error message after you resume the debug target process.

Look at this link, where the above quotes are sourced from.

This link also has a code example of someone who experienced this from a console app. It could be worth running that sample code to see if it triggers the issue on your system. The person who reported the issue also indicated it occurred intermittently, but running the code in Visual Studio debugging mode seemed to be the one common thread.

Possibly Microsoft fixed some root causes of the issue, but there are still other unfixed causes now surfacing.

Disable the service and it won't eat your memory again.

Tools->Options->Debugging->General, disable "Enable Diagnostic Tools while debugging".