Applications (especially big Java and C++ ones) often shows up as multiple lines in
htop, each have separate PID and separate nice level. Also application can spawn a lot of child processes (like as in
aptitude update), so I need to affect both parent one (to make new children have new priority) and child ones (to bring the effect immediately, not after the child terminates)
How can I apply "renice" or "ionice" or "schedtool" to already launched big application?