Dispatching in Computing: Task Scheduling and Execution Explained

Dispatching is the mechanism that assigns ready tasks to execution resources (CPU cores, threads, GPUs, nodes).

In Operating Systems

• Scheduler selects next task from run queue (priority, fairness, deadline, affinity).
• Dispatcher performs context switch: saves current register state, loads next task's state, jumps to its instruction pointer.
• Occurs on: time slice expiry, syscall, interrupt, lock contention, explicit yield.

In Parallel/Distributed Systems

• Task dispatchers (e.g., ThreadPoolExecutor, Celery, Kubernetes scheduler) match work units to workers.
• Strategies: FIFO, priority, locality-aware, load-balancing, speculative execution.

In Communications

• Message dispatching: Routing messages to handlers (event loops, actor systems, microservices).
• Patterns: pub/sub, request/reply, streaming.

Key Metrics

• Dispatch latency (queue → running)
• Throughput (tasks/sec)
• Fairness (starvation avoidance)
• Locality (cache/NUMA affinity)

Dispatching is the "traffic control" of computation — efficient dispatch maximizes hardware utilization and responsiveness.