Linux nice command: Run Process With Modified Scheduling Priority ( nicenesses )

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Q. How do I run a process with modified scheduling priority under Linux? I’d like to change the priority in the kernel’s scheduler while starting a command.

A. Use nice command to run a program with modified scheduling priority / nicenesses. Nicenesses range at least from -20 (resulting in the most favorable scheduling) through 19 (the least favorable). The default behavior is to increase the niceness by 10.

A niceness should not be confused with a scheduling priority, which lets applications determine the order in which threads are scheduled to run. Unlike a priority, a niceness is merely advice to the scheduler, which the scheduler is free to ignore.

nice syntax (/bin/nice command)

/bin/nice -n NUM

Add integer NUM (-20 to 19) to the niceness.

WARNING! There are multiple versions of the nice command. One built in to the shell, and one in /bin/nice. The syntax may be diffrent on your system. Refer your shell and /bin/nice command man page for details.

Change niceness by 3

Type the command as follows:
$ /bin/nice -n 3 command-name

Only a privileged user may run a process with lower niceness:
$ /bin/nice -n -1 command-name

Shell in build nice command syntax

If you use the csh or tcsh or bash, the syntax is as follows:
nice +n command
I recommend using /bin/nice syntax to avoid confusion and to save time.

Posted by: Vivek Gite

The author is the creator of nixCraft and a seasoned sysadmin and a trainer for the Linux operating system/Unix shell scripting. He has worked with global clients and in various industries, including IT, education, defense and space research, and the nonprofit sector. Follow him on Twitter, Facebook, Google+.

12 comment

        1. Seriously guys.. I’ve never had nice do much for my system scheduler/load wise. ionice seems to have a bit more impact for the ioscheduler.. but have you all ever really seen that much of an improvement on CPU bound processes and using nice on Linux?

          Tweeks

  1. A good example for using nice would be to use it when taring up a huge directory. If you think that is going to impact your IO and other applications running on the server, you can use nice as such

    nice -n 3 tar -cvf test.tar test_dir/*

  2. Does nice actually work? I’ve never seen much of a scheduling/priority/load change from nicing CPU hungry tasks. I have, however, heard good things about ionice for tweaking io-heavy apps. Maybe you should both nice and ionice a process that is going to hammer the CPU and IO.

    Tweeks

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