Meaning
Resource allocation techniques that restrict a specific software process or thread to a designated processor core prevent the operating system from migrating tasks between different pieces of hardware. Assignment of dedicated cores to sensitive applications reduces the performance penalties associated with context switching and interrupt handling. When cpu core pinning is implemented, the application maintains exclusive access to the execution units and local registers of the assigned core.
Processor Affinity
Soft affinity allows the scheduler to move a process if a core is overloaded, whereas hard affinity fixes the relationship until a manual change is made. Implementing cpu core pinning ensures that high-priority tasks are never delayed by the background activities of the kernel or other userspace programs. Isolation of resources is a primary step in moving from a pilot environment to a production system with guaranteed performance.
Cache Locality
Keeping a process on the same core maximizes the effectiveness of the local level one and level two caches. Data remains resident in the cache across multiple execution cycles because cpu core pinning prevents other threads from evicting it. Increased hit rates lead to more predictable execution times and lower overall latency for memory-intensive operations.
Scheduling Predictability
Deterministic performance is easier to achieve when the scheduler no longer has the authority to move threads across the system. This restriction minimizes the timing variation seen by applications that require sub-microsecond precision.
