Profile-Guided Optimization (PGO) has been shown to be useful not only in CPU-bound scenarios, but also in the mobile space where app size is a dominating issue. Collecting profiles on size-constrained devices is challenging because the instrumented binary can be doubled in size. Recently, we’ve introduced Lightweight Instrumentation that greatly improves the instrumented binary size overhead using debug info. In this talk we will describe how we reduced this overhead, how to create a minimal instrumented binary for function entry coverage only, and our future plans in this space.