SunOS man pages : priocntl (1)
User Commands priocntl(1)
NAME
priocntl - display or set scheduling parameters of specified
process(es)
SYNOPSIS
priocntl -l
priocntl -d [ -i idtype ] [ idlist ]
priocntl -s [ -c class ] [ class-specific options ] [
-i idtype ] [ idlist ]
priocntl -e [ -c class ] [ class-specific options ]
command [ argument(s) ]
DESCRIPTION
The priocntl command displays or sets scheduling parameters
of the specified process(es). It can also be used to display
the current configuration information for the system's pro-
cess scheduler or execute a command with specified schedul-
ing parameters.
Processes fall into distinct classes with a separate
scheduling policy applied to each class. The process classes
currently supported are the real-time class, time-sharing
class, and the interactive class. The characteristics of
these classes and the class-specific options they accept are
described below in the USAGE section under the headings
Real-Time Class, Time-Sharing Class, and Inter-Active
Class. With appropriate permissions, the priocntl command
can change the class and other scheduling parameters associ-
ated with a running process.
In the default configuration, a runnable real-time process
runs before any other process. Therefore, inappropriate use
of real-time processes can have a dramatic negative impact
on system performance.
If an idlist is present, it must appear last on the command
line and the elements of the list must be separated by white
space. If no idlist is present, an idtype argument of pid,
ppid, pgid, sid, taskid, class, uid, gid, or projid speci-
fies the process ID, parent process ID, process group ID,
session ID, task ID, class, user ID, group ID, or project
ID, respectively, of the priocntl command itself.
The command
priocntl -d [-i idtype] [idlist]
displays the class and class-specific scheduling parameters
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User Commands priocntl(1)
of the process(es) specified by idtype and idlist.
The command
priocntl -s [-c class] [class-specific options] [-i idtype] [idlist]
sets the class and class-specific parameters of the speci-
fied processes to the values given on the command line. The
-c class option specifies the class to be set. (The valid
class arguments are RT for real-time TS for time-sharing or
IA for inter-active.)
The class-specific parameters to be set are specified by the
class-specific options as explained under the appropriate
heading below. If the -c class option is omitted, idtype and
idlist must specify a set of processes which are all in the
same class, otherwise an error results. If no class-
specific options are specified, the process's class-specific
parameters are set to the default values for the class
specified by -c class (or to the default parameter values
for the process's current class if the -c class option is
also omitted).
In order to change the scheduling parameters of a process
using priocntl the real or effective user ID (respectively,
groupID) of the user invoking priocntl must match the real
or effective user ID (respectively, groupID) of the receiv-
ing process or the effective user ID of the user must be
super-user. These are the minimum permission requirements
enforced for all classes. An individual class may impose
additional permissions requirements when setting processes
to that class or when setting class-specific scheduling
parameters.
When idtype and idlist specify a set of processes, priocntl
acts on the processes in the set in an implementation-
specific order. If priocntl encounters an error for one or
more of the target processes, it may or may not continue
through the set of processes, depending on the nature of the
error.
If the error is related to permissions, priocntl prints an
error message and then continues through the process set,
resetting the parameters for all target processes for which
the user has appropriate permissions. If priocntl encounters
an error other than permissions, it does not continue
through the process set but prints an error message and
exits immediately.
A special sys scheduling class exists for the purpose of
scheduling the execution of certain special system processes
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User Commands priocntl(1)
(such as the swapper process). It is not possible to change
the class of any process to sys. In addition, any processes
in the sys class that are included in the set of processes
specified by idtype and idlist are disregarded by priocntl.
For example, if idtype were uid, an idlist consisting of a
zero would specify all processes with a UID of 0, except
processes in the sys class and (if changing the parameters
using the -s option) the init process.
The init process (process ID 1) is a special case. In order
for the priocntl command to change the class or other
scheduling parameters of the init process, idtype must be
pid and idlist must be consist of only a 1. The init process
may be assigned to any class configured on the system, but
the time-sharing class is almost always the appropriate
choice. (Other choices may be highly undesirable; see the
System Administration Guide, Volume 1 for more information.)
The command
priocntl -e [-c class] [class-specific options] command [argument...]
executes the specified command with the class and scheduling
parameters specified on the command line (arguments are the
arguments to the command). If the -c class option is omitted
the command is run in the user's current class.
OPTIONS
The following options are supported:
- c class
Specifies the class to be set. (The valid class argu-
ments are RT for real-time or TS for time-sharing or
IA for inter-active.) If the specified class is not
already configured, it will automatically be config-
ured.
-d Displays the scheduling parameters associated with a
set of processes.
-e Executes a specified command with the class and
scheduling parameters associated with a set of
processes.
-i idtype
This option, together with the idlist arguments (if
any), specifies one or more processes to which the
priocntl command is to apply. The interpretation of
idlist depends on the value of idtype. The valid
idtype arguments and corresponding interpretations of
idlist are as follows:
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User Commands priocntl(1)
- i pid
idlist is a list of process IDs. The priocntl
command applies to the specified processes.
-i ppid
idlist is a list of parent process IDs. The
priocntl command applies to all processes whose
parent process ID is in the list.
-i pgid
idlist is a list of process group IDs. The
priocntl command applies to all processes in the
specified process groups.
-i sid
idlist is a list of session IDs. The priocntl
command applies to all processes in the speci-
fied sessions.
-i taskid
idlist is a list of task IDs. The priocntl com-
mand applies to all processes in the specified
tasks.
-i class
idlist consists of a single class name (RT for
real-time or TS for time-sharing or IA for
inter-active). The priocntl command applies to
all processes in the specified class.
-i uid
idlist is a list of user IDs. The priocntl com-
mand applies to all processes with an effective
user ID equal to an ID from the list.
-i gid
idlist is a list of group IDs. The priocntl
command applies to all processes with an effec-
tive group ID equal to an ID from the list.
-i projid
idlist is a list of project IDs. The priocntl
command applies to all processes with an effec-
tive project ID equal to an ID from the list.
-i all
The priocntl command applies to all existing
processes. No idlist should be specified (if
one is specified, it is ignored). The permission
restrictions described below still apply.
If the -i idtype option is omitted when using the -d
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or -s options the default idtype of pid is assumed.
-l Displays a list of the classes currently configured in
the system along with class-specific information about
each class. The format of the class-specific informa-
tion displayed is described under USAGE.
-s Sets the scheduling parameters associated with a set
of processes.
The valid class-specific options for setting real-time
parameters are:
- p rtpri
Sets the real-time priority of the specified
process(es) to rtpri.
-t tqntm [-r res]
Sets the time quantum of the specified process(es) to
tqntm. You may optionally specify a resolution as
explained below.
The valid class-specific options for setting time-sharing
parameters are:
- m tsuprilim
Sets the user priority limit of the specified
process(es) to tsuprilim.
-p tsupri
Sets the user priority of the specified process(es) to
tsupri.
The valid class-specific options for setting inter-active
parameters are:
- m iauprilim
Sets the user priority limit of the specified
process(es) to iauprilim.
-p iaupri
Sets the user priority of the specified process(es) to
iaupri.
USAGE
Real-Time Class
The real-time class provides a fixed priority preemptive
scheduling policy for those processes requiring fast and
deterministic response and absolute user/application control
of scheduling priorities. If the real-time class is config-
ured in the system, it should have exclusive control of the
highest range of scheduling priorities on the system. This
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ensures that a runnable real-time process is given CPU ser-
vice before any process belonging to any other class.
The real-time class has a range of real-time priority
(rtpri) values that may be assigned to processes within the
class. Real-time priorities range from 0 to x, where the
value of x is configurable and can be displayed for a
specific installation that has already configured a real-
time scheduler, by using the command
priocntl -l
The real-time scheduling policy is a fixed priority policy.
The scheduling priority of a real-time process never changes
except as the result of an explicit request by the
user/application to change the rtpri value of the process.
For processes in the real-time class, the rtpri value is,
for all practical purposes, equivalent to the scheduling
priority of the process. The rtpri value completely deter-
mines the scheduling priority of a real-time process rela-
tive to other processes within its class. Numerically higher
rtpri values represent higher priorities. Since the real-
time class controls the highest range of scheduling priori-
ties in the system, it is guaranteed that the runnable
real-time process with the highest rtpri value is always
selected to run before any other process in the system.
In addition to providing control over priority, priocntl
provides for control over the length of the time quantum
allotted to processes in the real-time class. The time quan-
tum value specifies the maximum amount of time a process may
run, assuming that it does not complete or enter a resource
or event wait state (sleep). Notice that if another process
becomes runnable at a higher priority, the currently running
process may be preempted before receiving its full time
quantum.
The command
priocntl -d [-i idtype] [idlist]
displays the real-time priority and time quantum (in mil-
lisecond resolution) for each real-time process in the set
specified by idtype and idlist.
Any combination of the -p and -t options may be used with
priocntl -s or priocntl -e for the real-time class. If an
option is omitted and the process is currently real-time,
the associated parameter is unaffected. If an option is
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omitted when changing the class of a process to real-time
from some other class, the associated parameter is set to a
default value. The default value for rtpri is 0 and the
default for time quantum is dependent on the value of rtpri
and on the system configuration; see rt_dptbl(4).
When using the -t tqntm option, you may optionally specify a
resolution using the -r res option. (If no resolution is
specified, millisecond resolution is assumed.) If res is
specified, it must be a positive integer between 1 and
1,000,000,000 inclusively and the resolution used is the
reciprocal of res in seconds. For example, specifying -t 10
-r 100 would set the resolution to hundredths of a second
and the resulting time quantum length would be 10/100
seconds (one tenth of a second). Although very fine
(nanosecond) resolution may be specified, the time quantum
length is rounded up by the system to the next integral mul-
tiple of the system clock's resolution. Requests for time
quantums of zero or quantums greater than the (typically
very large) implementation-specific maximum quantum result
in an error.
In order to change the class of a process to real-time (from
any other class), the user invoking priocntl must have
super-user privilege. In order to change the rtpri value or
time quantum of a real-time process, the user invoking
priocntl must either be super-user, or must currently be in
the real-time class (shell running as a real-time process)
with a real or effective user ID matching the real or effec-
tive user ID of the target process.
The real-time priority and time quantum are inherited across
the fork(2) and exec(2) system calls.
Time-Sharing Class
The time-sharing scheduling policy provides for a fair and
effective allocation of the CPU resource among processes
with varying CPU consumption characteristics. The objectives
of the time-sharing policy are to provide good response time
to interactive processes and good throughput to CPU-bound
jobs, while providing a degree of user/application control
over scheduling.
The time-sharing class has a range of time-sharing user
priority (tsupri) values that may be assigned to processes
within the class. User priorities range from -x to +x, where
the value of x is configurable. The range for a specific
installation can be displayed by using the command
priocntl -l
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The purpose of the user priority is to provide some degree
of user/application control over the scheduling of processes
in the time-sharing class. Raising or lowering the tsupri
value of a process in the time-sharing class raises or
lowers the scheduling priority of the process. It is not
guaranteed, however, that a time-sharing process with a
higher tsupri value will run before one with a lower tsupri
value. This is because the tsupri value is just one factor
used to determine the scheduling priority of a time-sharing
process. The system may dynamically adjust the internal
scheduling priority of a time-sharing process based on other
factors such as recent CPU usage.
In addition to the system-wide limits on user priority
(displayed with priocntl -l), there is a per process user
priority limit (tsuprilim), which specifies the maximum
tsupri value that may be set for a given process.
The command
priocntl -d [-i idtype] [idlist]
displays the user priority and user priority limit for each
time-sharing process in the set specified by idtype and
idlist.
Any time-sharing process may lower its own tsuprilim (or
that of another process with the same user ID). Only a
time-sharing process with super-user privilege may raise a
tsuprilim. When changing the class of a process to time-
sharing from some other class, super-user privilege is
required in order to set the initial tsuprilim to a value
greater than zero.
Any time-sharing process may set its own tsupri (or that of
another process with the same user ID) to any value less
than or equal to the process's tsuprilim. Attempts to set
the tsupri above the tsuprilim (and/or set the tsuprilim
below the tsupri) result in the tsupri being set equal to
the tsuprilim.
Any combination of the -m and -p options may be used with
priocntl -s or priocntl -e for the time-sharing class. If an
option is omitted and the process is currently time-sharing,
the associated parameter is normally unaffected. The excep-
tion is when the -p option is omitted and -m is used to set
a tsuprilim below the current tsupri. In this case, the
tsupri is set equal to the tsuprilim which is being set. If
an option is omitted when changing the class of a process to
time-sharing from some other class, the associated parameter
is set to a default value. The default value for tsuprilim
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is 0 and the default for tsupri is to set it equal to the
tsuprilim value which is being set.
The time-sharing user priority and user priority limit are
inherited across the fork(2) and exec(2) system calls.
Inter-Active Class
The inter-active scheduling policy provides for a fair and
effective allocation of the CPU resource among processes
with varying CPU consumption characteristics while providing
good responsiveness for user interaction. The objectives of
the inter-active policy are to provide good response time to
interactive processes and good throughput to CPU-bound jobs.
The priorities of processes in the inter-active class can be
changed in the same manner as those in the time-sharing
class, though the modified priorities will continue to be
adjusted to provide good responsiveness for user interac-
tion.
EXAMPLES
Real-Time Class examples follow:
Example 1: Setting the class of any non-real-time processes
This example sets the class of any non-real-time processes
selected by idtype and idlist to real-time and sets their
real-time priority to the default value of 0. The real-time
priorities of any processes currently in the real-time class
are unaffected. The time quantums of all of the specified
processes are set to 1/10 seconds
example% priocntl -s -c RT -t 1 -r 10 -i idtype idlist
Example 2: Executing a command in real-time
This example executes command in the real-time class with a
real-time priority of 15 and a time quantum of 20 mil-
liseconds:
example% priocntl -e -c RT -p 15 -t 20 command
Time-Sharing Class examples follow:
Example 3: Setting the class of non-time-sharing processes
This example sets the class of any non-time-sharing
processes selected by idtype and idlist to time-sharing and
sets both their user priority limit and user priority to 0.
Processes already in the time-sharing class are unaffected.
example% priocntl -s -c TS -i idtype idlist
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Example 4: Executing a command in the time-sharing class
This example executes command with the arguments arguments
in the time-sharing class with a user priority limit of 0
and a user priority of -15:
example% priocntl -e -c TS -m 0 -p -15 command [arguments]
EXIT STATUS
The following exit values are returned:
For options -d, -l, and -s:
0 Successful operation.
1 Error condition.
For option -e:
Return of the Exit Status of the executed command denotes
successful operation. Otherwise,
1 Command could not be executed at the specified prior-
ity.
ATTRIBUTES
See attributes(5) for descriptions of the following attri-
butes:
____________________________________________________________
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
|_____________________________|_____________________________|
| Availability | SUNWcsu |
|_____________________________|_____________________________|
| CSI | Enabled |
|_____________________________|_____________________________|
SEE ALSO
nice(1), ps(1), exec(2), fork(2), priocntl(2), rt_dptbl( 4),
attributes(5)
System Administration Guide, Volume 1
DIAGNOSTICS
priocntl prints the following error messages:
Process(es) not found
None of the specified processes exists.
Specified processes from different classes
The -s option is being used to set parameters, the -c
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class option is not present, and processes from more
than one class are specified.
Invalid option or argument
An unrecognized or invalid option or option argument
is used.
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