Reduce background compression thread priority
As I understand, the compression is not latency-sensitive, i.e. if we get it done 30 seconds or 1 minute later, nobody really minds, but if we process 10000 packets 200 ms slower, that materially affects user experience. Also, I think if you do not set the thread priority, modern schedulers may assume that because it runs infrequently, the compression task is a "foreground" or "interactive" task and the actual cell relaying is a "background" task that may be slowed down to minimize user impact, exactly the opposite of what we want.
Therefore, this should improve single-CPU relay performance (and multi-CPU relay performance once we implement better multithreading).