> under such load server is experience somewhat to "general network > delays", network conections become slow (both incoming and outgoing), > sometimes even 5 sec on 1G network.
It sounds unlikely that CPU congestion is responsible for 5 s network delays unless your hardware is significantly underrated. Are you 100% sure that manually reserving CPUs for specific tasks is going to solve this dilemma? Note that most of the time when you seemingly run out of CPU horse power you actually clog your memory bus, and assigning one CPU to one task won't solve this.
