To prevent a website on shared hosting from using more system resources than other websites, you can limit resource usage per subscription using the Plesk Cgroups Manager extension. Plesk supports limits on CPU, RAM, and disk read/write bandwidth usage.
To ensure that the limits are not exceeded, Plesk uses a Linux kernel feature called Control Groups (cgroups). It calculates resource usage per system user, or, in other words, per Plesk subscription, and monitors the resource consumption. If a subscription consumes more resources than allowed, the operating system restricts the consumption of resources by this subscription.
You can set limits at two levels - the service plan level and the subscription level. Subscriptions will have limits that were defined in their service plan unless you edit limits for individual subscriptions. Plesk offers three ways of setting the limits: using the Plesk UI, command line interface (see the service_plan and subscription_settings utilities in the Reference for Command-Line Utilities), or API (see Managing Service Plans and Managing Subscriptions sections in the XML API Guide).