I'm guessing that the time required to open the hosts file for reading would eclipse the amount of time required to parse it and do a linear search on the entri

I'm guessing that the time required to open the hosts file for reading would eclipse the amount of time required to parse it and do a linear search on the entries. I would think that the file would have to be measured in the hundreds of megabytes for performance to be a significant consideration, but I haven't benchmarked it.