App for monitoring L3 usage?

Is there an app that allows you to monitor L3 cache usage? There are a couple of projects now, where this is necessary to know, where making sure the tasks don't exceed the L3.

Edit: searching around, I found a couple references to perfmon (windows). I launched it, and found a category for cache, but no idea how to use the tool, or interpret the data.

Edit 2: Yes, I understand all caches are always full. In short, I am looking for a way to monitor if I am exceeding the L3 and causing tasks to go to RAM, with the number of tasks I am running.