Reduce memory usage

Memory usage of cargo tally can get quite severe. Running cargo tally winapi windows-sys peaked at 12.7 GB, which isn't terrible (but also far from great). However, when trying it with --transitive, the program exhausts my 32 GB of RAM and 8 GB of swap before Linux kills it as OOM, so it apparently uses in excess of 40 GB.

Is it somehow possible to reduce the amount of memory used? I don't mind if it takes longer to run; the speed is reasonable as-is. Perhaps if some data could be written to disk (and later read back as needed) if memory usage exceeds a threshold?