Managing Process Class Information
The following list identifies the process scheduling classes that can be configured on your system, and the user priority range for the timesharing class. The possible process scheduling classes are as follows:
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Fair share (FSS)
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Fixed (FX)
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System (SYS)
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Interactive (IA)
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Real-time (RT)
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The priority of a process is inherited from the parent process. This priority is referred to as the user-mode priority.
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The system looks up the user-mode priority in the timesharing dispatch parameter table and adds in any nice or priocntl (user-supplied) priority and ensures a 0–59 range to create a global priority.
Changing the Scheduling Priority of Processes (priocntl)
The scheduling priority of a process is the priority assigned by the process scheduler, according to scheduling policies. The dispadmin command lists the default scheduling policies.
You can use the priocntl command to assign processes to a priority class and to manage process priorities. For instructions on using the priocntl command to manage processes, see How to Designate a Process Priority (priocntl).
How to Display Basic Information About Process Classes (priocntl)
You can display process scheduling classes and priority ranges with the priocntl -l command.
$ priocntl -l |
Example—Getting Basic Information About Process Classes (priocntl)
The following example shows output from the priocntl -l command.
# priocntl -l
CONFIGURED CLASSES
==================
SYS (System Class)
TS (Time Sharing)
Configured TS User Priority Range: -60 through 60
FX (Fixed priority)
Configured FX User Priority Range: 0 through 60
IA (Interactive)
Configured IA User Priority Range: -60 through 60
|
How to Display the Global Priority of a Process
You can display the global priority of a process by using the ps command.
$ ps -ecl |
The global priority is listed under the PRI column.
Example—Displaying the Global Priority of a Process
The following example shows ps -ecl command output. The values in the PRI column show that the pageout process has the highest priority, while sh has the lowest.
$ ps -ecl F S UID PID PPID CLS PRI ADDR SZ WCHAN TTY TIME COMD 19 T 0 0 0 SYS 96 f00d05a8 0 ? 0:03 sched 8 S 0 1 0 TS 50 ff0f4678 185 ff0f4848 ? 36:51 init 19 S 0 2 0 SYS 98 ff0f4018 0 f00c645c ? 0:01 pageout 19 S 0 3 0 SYS 60 ff0f5998 0 f00d0c68 ? 241:01 fsflush 8 S 0 269 1 TS 58 ff0f5338 303 ff49837e ? 0:07 sac 8 S 0 204 1 TS 43 ff2f6008 50 ff2f606e console 0:02 sh |
How to Designate a Process Priority (priocntl)
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Start a process with a designated priority.
# priocntl -e -c class -m userlimit -p pri command-name
-e
Executes the command.
-c class
Specifies the class within which to run the process. The valid classes are TS (timesharing), RT (real time), IA (interactive), FSS (fair share), or FX (fixed priority).
-m userlimit
Specifies the maximum amount you can raise or lower your priority, when using the -p option.
-p pri command-name
Lets you specify the relative priority in the RT class, for a real-time thread. For a timesharing process, the -p option lets you specify the user-supplied priority, which ranges from -60 to +60.
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Verify the process status.
# ps -ecl | grep command-name
Example—Designating a Process Priority (priocntl)
The following example shows how to start the find command with the highest possible user-supplied priority.
# priocntl -e -c TS -m 60 -p 60 find . -name core -print # ps -ecl | grep find |
How to Change Scheduling Parameters of a Timesharing Process (priocntl)
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Change the scheduling parameters of a running timesharing process.
# priocntl -s -m userlimit [-p userpriority] -i idtype idlist
-s
Lets you set the upper limit on the user priority range and change the current priority.
-m userlimit
Specifies the maximum amount you can raise or lower your priority, when you use the -p option.
-p userpriority
Allows you to designate a priority.
-i idtype idlist
Uses a combination of idtype and idlist to identify the process or processes. The idtype specifies the type of ID, such as pid or UID. Use idlist to identify a list of pids or UIDs.
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Verify the process status.
# ps -ecl | grep idlist
Example—Changing Scheduling Parameters of a Timesharing Process (priocntl)
The following example shows how to execute a command with a 500-millisecond time slice, a priority of 20 in the RT class, and a global priority of 120.
# priocntl -e -c RT -t 500 -p 20 myprog # ps -ecl | grep myprog |
How to Change the Class of a Process (priocntl)
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Note –You must be superuser or working in a real-time shell to change a process from, or to, a real-time process.
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Change the class of a process.
# priocntl -s -c class -i idtype idlist
-s
Lets you set the upper limit on the user priority range and change the current priority.
-c class
Specifies the class, TS or RT, to which you are changing the process.
-i idtype idlist
Uses a combination of idtype and idlist to identify the process or processes. The idtype specifies the type of ID, such as pid or UID. Use idlist to identify a list of pids or UIDs.
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Verify the process status.
# ps -ecl | grep idlist
Example—Changing the Class of a Process (priocntl)
The following example shows how to change all the processes belonging to user 15249 to real-time processes.
# priocntl -s -c RT -i uid 15249 # ps -ecl | grep 15249 |
Note –
If, as superuser, you change a user process to the real-time class, the user cannot subsequently change the real-time scheduling parameters by using the priocntl -s command.
Changing the Priority of a Timesharing Process (nice)
The nice command is only supported for backward compatibility to previous Solaris releases. The priocntl command provides more flexibility in managing processes.
The priority of a process is determined by the policies of its scheduling class, and by its nice number. Each timesharing process has a global priority. The global priority is calculated by adding the user-supplied priority, which can be influenced by the nice or priocntl commands, and the system-calculated priority.
The execution priority number of a process is assigned by the operating system, and is determined by several factors, including its scheduling class, how much CPU time it has used, and in the case of a timesharing process, its nice number.
Each timesharing process starts with a default nice number, which it inherits from its parent process. The nice number is shown in the NI column of the ps report.
A user can lower the priority of a process by increasing its user-supplied priority. But only superuser can lower a nice number to increase the priority of a process. This restriction prevents users from increasing the priorities of their own processes, thereby monopolizing a greater share of the CPU.
The nice numbers range between 0 and +39, with 0 representing the highest priority. The default nice value for each timesharing process is 20. Two versions of the command are available, the standard version, /usr/bin/nice, and the C shell built-in command.
How to Change the Priority of a Process (nice)
Note –
This section describes the syntax of the /usr/bin/nice command and not the C-shell nice built-in command. For information about the C-shell nice command, see csh(1).
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Determine whether you want to lower the priority of a command as a user or raise or lower the priority of a command as superuser and select one of the following:
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Follow the examples in step 2 to lower the priority of a command as a user.
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Follow the examples in step 3 to raise or lower priorities of a command as superuser.
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As a user, lower the priority of a command by increasing the nice number.
The following nice command executes command-name with a lower priority by raising the nice number by 5 units.
In the preceding command, the minus sign designates that what follows is an option. This command could also be specified as follows:
$ /usr/bin/nice -5 command-name
% /usr/bin/nice -n 5 command-name
The following nice command lowers the priority of command-name by raising the nice number by the default increment of 10 units, but not beyond the maximum value of 39.
% /usr/bin/nice command-name
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As superuser, raise or lower the priority of a command by changing the nice number.
The following nice command raises the priority of command-name by lowering the nice number by 10 units, but not below the minimum value of 0.
# /usr/bin/nice --10 command-name
In the preceding command, the first minus sign designates that what follows is an option. The second minus sign indicates a negative number.
The following nice command lowers the priority of command-name by raising the nice number by 5 units, but not beyond the maximum value of 39.
# /usr/bin/nice -5 command-name
For more information, see nice(1).
Troubleshooting Problems With System Processes
Here are some tips on obvious problems you might find:
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Look for several identical jobs that are owned by the same user. This problem might occur because of a running script that starts a lot of background jobs without waiting for any of the jobs to finish.
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Look for a process that has accumulated a large amount of CPU time. You can identify this problem by checking the TIME field in the ps output. Possibly, the process is in an endless loop.
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Look for a process that is running with a priority that is too high. Use the ps -c command to see the CLS field, which displays the scheduling class of each process. A process executing as a real-time (RT) process can monopolize the CPU. Or, look for a timesharing (TS) process with a high nice number. A user with superuser privileges might have increased the priority of a process. The system administrator can lower the priority by using the nice command.
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Look for a runaway process. A runaway process progressively uses more and more CPU time. You can identify this problem by looking at the time when the process started (STIME) and by watching the cumulation of CPU time (TIME) for a while.
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