Are generational garbage collectors inherently cache-friendly?
Here are a few papers that talk about the cache implications of generational garbage collectors:


Caching Considerations for Generational Garbage Collection
The Effect of Garbage Collection on Cache Performance


From what I can gather, the primary issue is that garbage collected systems trade off space in memory to avoid up front collection. The same thing applies to cache memory. As you suggested, the things in the first generation are most likely going to be sitting in cache, and so their allocation and collection will be much faster than something in main memory, or paged out to disk. The main issue is the size of the first generation with respect to the size of your cache. If your cache fills up before the first generation does, then you start to lose those benefits as the misses start piling up.