This issue addresses a couple of performance improvements when creating the HostDb:
- avoid needless conversions between hostname and URL
- improvements of HostDb serialization (write and read)
- parametrize logging and log less on level INFO
- do not create DNS resolver threads if DNS look-ups are not requested by command-line options
A patch/PR is ready. Depending on the chosen command-line options, a 10-20% speed-up should be visible if DNS look-ups, normalization and filtering are off.