Hard to tell without having `somelargefile.nt.gz` to test with. But some general ideas:
* Did you compile with `-d:release`? Debug builds can be pretty slow * For benchmarking you should really use `std/monotimes` instead of `cpuTime`, but I doubt this would change much. * Not sure how optimised the standard library gzip is, you might want to try <https://github.com/guzba/zippy> instead
