Controlling Access to System Resources

Use the systemctl command to control a cgroup's access to system resources, for example:

sudo systemctl [--runtime] set-property httpd CPUShares=512 MemoryLimit=1G

CPUShare controls access to CPU resources. As the default value is 1024, a value of 512 halves the access to CPU time that the processes in the cgroup have. Similarly, MemoryLimit controls the maximum amount of memory that the cgroup can use.

Note:

You don't need to specify the .service extension to the name of a service.

If you specify the --runtime option, the setting doesn't persist across system reboots.

Alternatively, you can change the resource settings for a service under the [Service] heading in the service's configuration file in /usr/lib/systemd/system. After editing the file, make systemd reload its configuration files and then restart the service:

sudo systemctl daemon-reload
sudo systemctl restart service

You can run general commands within scopes and use systemctl to control the access that these transient cgroups have to system resources. To run a command within in a scope, use the systemd-run command:

sudo systemd-run --scope --unit=group_name [--slice=slice_name]

If you don't want to create the group under the default system slice, you can specify another slice or the name of a new slice. The following example runs a command named mymonitor in mymon.scope under myslice.slice:

sudo systemd-run --scope --unit=mymon --slice=myslice mymonitor

Running as unit mymon.scope.

Note:

If you don't specify the --scope option, the control group is a created as a service rather than as a scope.

You can then use systemctl to control the access that a scope has to system resources in the same way as for a service. However, unlike a service, you must specify the .scope extension, for example:

sudo systemctl --runtime set-property mymon.scope CPUShares=256

For more information see About Control Groups and the systemctl(1), systemd-cgls(1), and systemd.resource-control(5) manual pages.