Ah, missed that. Thanks!
The straight read speed should be really fast now, but when we are updating while reading, when we get to the end of the file we are reading, we have to try and open it again to see if there is anything new. The local fs impl uses channels and doesn't have to do this to see the latest data from the writer. So even when updates are also coming in, this should be a huge improvement, because it was previously reopening needlessly on every update it read, but we do still have to take that hit of opening a new reader every time we read up to the end of the view of the last reader.