I have not tried this option, but Incremental backup seems to be slow #3212 has some information from @mr-flibble about its behavior. Unfortunately, the person who opened the issue didn’t find a performance increase simply from this option, so went looking for others. Possibly the CPU use you’re seeing is not the counting but processing, which I think is overlapped. You can see some information and a setting at –synchronous-upload. [solved] Improve Performance for unchanged files might also help if your backup isn’t finding a lot of changes.