Researchers have devoted decades towards improving garbage collection performance. A key question is: What opportunity remains for performance improvement? Because the perceived performance disadvantage of garbage collection is often cited as a barrier to its adoption, we propose using explicit memory management as the touchstone for evaluating garbage collection performance. This work begins by asking how well garbage collection performs currently and which areas remain for it to improve. We present oracular memory management to help answer this question by enabling us to quantify garbage collection's performance. Our results show that while garbage collection can perform competitively, this good performance assumes the heap fits in available memory. Our work thus focuses onto this brittleness, and we show the design and implement of our bookmarking collector. While performing competitively when not paging, our new collector's paging performance helps make garbage collection's performance more robust.