perPID

perPID is a term used in computing to describe approaches that attribute, enforce, or monitor resources and policies on an individual process identified by its process identifier (PID). It is not a formal standard but a descriptive label for mechanisms that operate at the granularity of a single process, often within operating systems, container runtimes, and monitoring tools. The core idea is to associate behavior or accounting with a specific PID to enable precise control, auditing, or analysis.

In operating systems, per-PID accounting collects and attributes resource usage such as CPU time, memory, and I/O to each process. This enables administrators to measure activity, enforce quotas, or trigger actions when usage crosses thresholds. Linux provides per-PID data through the proc filesystem and related tools, while resource controllers and cgroups allow grouping of processes to apply limits or priorities, sometimes on a per-PID basis within larger containment strategies.

In containerization and virtualization, perPID isolation is often achieved with namespace separation, particularly PID namespaces. Each container receives its own isolated PID space, so processes inside a container cannot observe or signal processes in another namespace. This per-PID isolation is a key enabler of multi-tenant deployment, ensuring predictable process visibility and security boundaries.

In security and auditing, per-PID policies link events, privileges, and controls to the originating process, supporting detailed tracing and enforcement. This can complement broader access controls, capability handling, and process ancestry tracking.

Limitations include the reuse of PIDs after process termination and the complexities of namespace-scoped visibility, which can complicate accounting and security models. Effective perPID implementations often rely on combinations of PIDs, namespaces, cgroups, and access-control mechanisms to provide robust management. See also: process ID, pid namespace, cgroups, process accounting.