Difference between revisions of "Process Niceness"

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renice - change process priority real time.
 
renice - change process priority real time.
  
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A kernel scheduler is a unit of the kernel that determines the most suitable process out of all runnable processes to execute next. 
  
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There are a total of 140 priorities and two distinct priority ranges implemented in Linux. The first one is a nice value (niceness) which ranges from -20 (highest priority value) to 19 (lowest priority value) and the default is 0.
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* niceness of -20 gives the process the most priority
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* niceness of 19 gives the process the least priority
  
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Total number of priorities = 140
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Real time priority range(PR or PRI):  0 to 99
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User space priority range: 100 to 139
  
 
=== check nice level setting ===
 
=== check nice level setting ===
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One way
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ps -eo pid,ppid,ni,comm
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This will list the process ID, the nice level, and the actual command.
 
This will list the process ID, the nice level, and the actual command.
 
  ps ax -o pid,ni,cmd
 
  ps ax -o pid,ni,cmd
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  sudo apt install htop
 
  sudo apt install htop
  
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=== changing the program priority ===
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nice runs commands at increased priority, renice can raise or lower but works for processes that are already running.
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*If no value is provided, nice sets a priority of 10 by default.
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*A command or program run without nice defaults to a priority of zero.
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*Only root can run a command or program with increased or high priority.
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*Normal users can only run a command or program with low priority.
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 +
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you can use the ionice command to start the process with low io priority:
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nice -n18 ionice -c3 /path/to/mydaemon
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How to renice all threads (and children) of one process
  
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The kernel only handles "runnable entities", that is, something which can be run and scheduled.  A thread, is just a kind of process that shares (at least) memory space and signal handlers with another one.
  
  

Revision as of 19:45, 27 May 2020

NICE and RENICE

nice - set process scheduling priority

renice - change process priority real time.

A kernel scheduler is a unit of the kernel that determines the most suitable process out of all runnable processes to execute next.

There are a total of 140 priorities and two distinct priority ranges implemented in Linux. The first one is a nice value (niceness) which ranges from -20 (highest priority value) to 19 (lowest priority value) and the default is 0.

  • niceness of -20 gives the process the most priority
  • niceness of 19 gives the process the least priority
Total number of priorities = 140
Real time priority range(PR or PRI):  0 to 99 
User space priority range: 100 to 139

check nice level setting

One way

ps -eo pid,ppid,ni,comm

This will list the process ID, the nice level, and the actual command.

ps ax -o pid,ni,cmd

Using the htop command will show nice level. This requires installation. For Ubuntu/Mint:

sudo apt install htop

changing the program priority

nice runs commands at increased priority, renice can raise or lower but works for processes that are already running.

  • If no value is provided, nice sets a priority of 10 by default.
  • A command or program run without nice defaults to a priority of zero.
  • Only root can run a command or program with increased or high priority.
  • Normal users can only run a command or program with low priority.


you can use the ionice command to start the process with low io priority:

nice -n18 ionice -c3 /path/to/mydaemon

How to renice all threads (and children) of one process

The kernel only handles "runnable entities", that is, something which can be run and scheduled. A thread, is just a kind of process that shares (at least) memory space and signal handlers with another one.