Using the exact number of cores I have as the argument (from /proc/cpuinfo) makes the compilation go smooth. Are you saying that without an argument, Make uses a very high default number that causes other processes to starve ? Nevertheless, kernel shouldnt allow such a situation as far as I understrand, and perhaps should be considered a bug in the kernel ?
Blame HDMI forum for that. They objected to AMD releasing open source driver for HDMI 2.0+ that lets you do higher modes like 4k60 or 5k etc due to patent reasons. DisplayPort folks on the other hand, had no objections. DP is quite a superior technology too, so if you could, use it instead of HDMI please.