Linux under nice/renice Command summary __linux

Linux under nice/renice command summary2010-03-30 12:58 1.1.1 Nice Command

The kernel determines how much processor time the process requires, depending on the nice value of the process. The value range for the nice value is:-20 to 20. A process with a nice value of 20 has a high priority. A process with a nice value of 20 has a low priority.

1 to display the nice value of all running processes with PS Axl

# PS Axl

F UID PID PPID PRI NI VSZ RSS wchan STAT TTY time COMMAND

4 0 1 0 0 2172 552-s? 0:17 Init [5]

1 0 3 1 0 0 ksofti SN? 3:18 [ksoftirqd/0]

1 0 1 5-10 0 0 worker s<? 0:01 [events/0]

4 0 5145 1 32124 18592-sns? 0:08/usr/bin/python/usr/bin/rhn-applet-gui--sm-client-id DEFAULT4

4 0 5147 5142 0 3528 604-s? 0:00/sbin/pam_timestamp_check-d Root

1 503 17552 4180 0 14208 3920-s? 0:01/home/www/apache2/bin/httpd-f/home/www/apache2/conf/httpd.conf-k Start

2 How to assign a low priority to a shell script (a higher nice value)?

In the following example, when I start the nice-test.sh script in the background, the nice value is 0.

$./nice-test.sh &

[3] 13009

$ ps Axl | grep nice-test

0 509 13009 12863 0 4652 972 wait S pts/1 0:00/bin/bash./nice-test.sh

[Note: The Sixth column value is a nice value of 0]

Now, execute the same script with a different nice value, as follows:

$ nice-10./nice-test.sh &

[1] 13016

$ ps Axl | grep nice-test

0 509 13016 12863 4236 968 wait SN pts/1 0:00/bin/bash./nice-test.sh

[Note: The sixth column value of 10 is the nice value for the shell script]

3 How to assign a high priority to a shell script (lower nice value)?

In the following example, a nice value of "-10" is assigned to the shell script nice-test.sh.

$ nice--10/nice-test.sh &

[1] 13021

$ nice:cannot Set Priority:permission denied

Note: Only the root user can set a negative nice value. Log on again with root user. Notice that there is a double dash in front of 10 in the Nice command below.

# nice--10/nice-test.sh &

[1] 13060

# PS Axl | grep nice-test

4 0 13060 13024 10-10 5388 964 wait s< pts/1 0:00/bin/bash./nice-test.sh

[Note: The Sixth column value is-10 is the nice value of the shell script]

1.1.2 Renice Command

Renice can set the scheduling priority for a running process.

1 How to reduce the priority of a running process (add nice value)?

In the following example, the nice value for a existing shell script is 10. (6th column of PS output)

$ ps Axl | grep nice-test

0 509 13245 13216 5244 968 wait SN pts/1 0:00/bin/bash./nice-test.sh

To increase the Nice value (and therefore lower the priority), execute the renice command as follows.

$ renice 16-p 13245

13245:old priority, new priority 16

$ ps Axl | grep nice-test

0 509 13245 13216 5244 968 wait SN pts/1 0:00/bin/bash./nice-test.sh

[Note: Now, the 6th column of nice-test.sh (PID 13245) shows that the new nice value is 16]

2 How do I increase the priority of the running process (reduce the nice value)?

In the following example, an existing shell script runs with a nice value of 10. (PS output 6th column)

$ ps Axl | grep nice-test

0 509 13254 13216 4412 968 wait SN pts/1 0:00/bin/bash./nice-test.sh

To elevate its priority, give it a lower nice value. However, only root can elevate the priority of the running process, otherwise you will get the following error message.

$ renice 5-p 13254

Renice:13254:setpriority:permission denied

Login as root to increase the priority of a running

Process

$ Su-

# Renice 5-p 13254

13254:old priority, new priority 5

# PS Axl | grep nice-test

0 509 13254 13216 5 4412 968 wait SN pts/1 0:00/bin/bash./nice-test.sh

Note: The 6th column now shows a lower nice value of 5 (elevated priority)]

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