Using Resource Controls

How to Set the Maximum Number of LWPs for Each Task in a Project

Type this entry in the /etc/project database to set the maximum number of LWPs in each task in project x-files to 3.

x-files:100::root::task.max-lwps=(privileged,3,deny)

When superuser creates a new task in project x-files by joining it with newtask, superuser will not be able to create more than three LWPs while running in this task. This is shown in the following annotated sample session.

# newtask -p x-files csh

# prctl -n task.max-lwps $$
688: csh
task.max-lwps
                            3 privileged deny
                   2147483647 system     deny
# id -p
uid=0(root) gid=1(other) projid=100(x-files)

# ps -o project,taskid -p $$
 PROJECT TASKID
 x-files   236

# csh        /* creates second LWP */

# csh        /* creates third LWP */

# csh        /* cannot create more LWPs */
Vfork failed

#

How to Set Multiple Controls on a Project

The /etc/project file can contain settings for multiple resource controls for each project as well as multiple threshold values for each control. Threshold values are defined in action clauses, which are comma-separated for multiple values.

The following line in the file sets a basic control with no action on the maximum LWPs per task for project x-files. The line also sets a privileged deny control on the maximum LWPs per task. This control causes any LWP creation that exceeds the maximum to fail, as shown in the previous example. Finally, the maximum file descriptors per process are limited at the basic level, which forces failure of any open call that exceeds the maximum.

x-files:101::root::task.max-lwps=(basic,10,none),(privileged,500,deny);
    process.max-file-descriptor=(basic,128,deny)

How to Use prctl

As superuser, type prctl to display the maximum file descriptor for the current shell that is running:

# prctl -n process.max-file-descriptor $$
8437:   sh
process.max-file-descriptor              [ lowerable deny ]
                          256 basic      deny
                        65536 privileged deny
                   2147483647 system     deny

Use the prctl command to temporarily add a new privileged value to deny the use of more than three LWPs per task for the x-files project. The result is identical to the result in How to Set the Maximum Number of LWPs for Each Task in a Project, as shown in the following annotated sample session:

# newtask -p x-files

# id -p
uid=0(root) gid=1(other) projid=101(x-files)

# prctl -n task.max-lwps -t privileged -v 3 -e deny -i project x-files

# prctl -n task.max-lwps -i project x-files
670:    sh
task.max-lwps
                            3 privileged deny
                   2147483647 system     deny

You can also use prctl -r to change the lowest value of a resource control.

# prctl -n process.max-file-descriptor -r -v 128 $$

How to Use rctladm

You can use rctladm to enable the global syslog attribute of a resource control. When the control is exceeded, notification is logged at the specified syslog level. Type the following:

# rctladm -e syslog process.max-file-descriptor