Table of Content
Weight: 2
Description: Candidates should should be able to manage process execution priorities.
Key Knowledge Areas:
- Know the default priority of a job that is created
- Run a program with higher or lower priority than the default
- Change the priority of a running process
Terms and Utilities:
nice ps renice top
nice
range -20(high) to 19(low) default is 10 root@dclab-u1504s:~# ps -l F S UID PID PPID C PRI NI ADDR SZ WCHAN TTY TIME CMD 4 S 0 2021 1909 0 80 0 - 12510 wait pts/0 00:00:00 su 4 S 0 2022 2021 0 80 0 - 5639 wait pts/0 00:00:00 bash 0 R 0 2049 2022 0 80 0 - 2512 - pts/0 00:00:00 ps root@dclab-u1504s:~# nice 0 nice --18 top # nice -18 renice -newnice• renice +1 p 14292 – make process 14292 just a little nicer • renice +2 u jack – make all of Jack's processes two notches nicer. • renice +3 g users – make the processes whose group is “users” three notches nicer.
Quiz questions
1. Why would one want to run a process with a lower priority? 2. How does one run a process with a lower priority? 3. How does one increase the priority of a process when running it? Who can do this? 4. How do you change the priority of a running process? 5. What key in top changes the priority of an existing process?
Answers to quiz questions
1. So that the process does not interfere with processes which should be running more urgently. 2. nice process 3. nice -n -20 process ... only root 4. renice +2 pid ... make process 2 notches less important 5. r for renice