Working on my personal indexing service, I noticed that large files were getting OOM killed. That’s surprising because rust makes it fairly difficult to do bad things with memory (you can roughly approximate where memory is dropped just by reading code).
After strugging to find a memory profiler for macOS (and not even being able to install Xcode for some reason), I settled on a stupid solution using Activity Monitor which comes pre-installed on every Mac. First, I changed the main method to execute just the code path I suspected was resulting in large memory usage (calculating embeddings) after adding logging to see which file was being worked on before getting OOM killed. Next, I opened Activity Monitor to the Memory tab and typed the name of the rust crate in the search box. Since names are consistent when running cargo run, I could see the value of memory used which gets sampled every second or so. I tried a few code changes, reran it each time, and voila—fixed! Sometimes all you need is a fast feedback loop.