rt/wiki, cpuset (cset) Tutorial, here.
Although any set up of cpusets can really be described as “shielding,” there is one prevalent shielding model in use that is so common that cset has a subcommand that is dedicated to its use. This subcommand is called shield.
The concept behind this model is the use of three cpusets. The root cpuset which is always present in all configurations and contains all CPUs. The system cpuset which contains CPUs which are used for system tasks. These are the normal tasks that are not “important,” but which need to run on the system. And finally, the user cpuset which contains CPUs which are used for “important” tasks. The user cpuset is the shield. Only those tasks that are somehow important, usually tasks whose performance determines the overall rating for the machine, are run in the user cpuset.
The shield subcommand manages all of these cpusets and lets you define the CPUs and Memory Nodes that are in the shielded and unshielded sets. The subcommand automatically moves all movable tasks on the system into the unshielded cpuset on shield activation, and back into the root cpuset on shield tear down. The subcommand then lets you move tasks into and out of the shield. Additionally, you can move special tasks (kernel threads) which normally run in the root cpuset into the unshielded set so that your shield will have even less disturbance.
The shield subcommand abstracts the management of these cpusets away from you and provides options that drive how the shield is set up, which tasks are to be shielded and which tasks are not, and status of the shield. In fact, you need not be bothered with the naming of the required cpusets or even where the cpuset filesystem is mounted. Cset and the shield subcommand takes care of all that.
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