Numjobs

Numjobs is a term used in computing to denote the number of jobs or tasks that may run concurrently in a system, workflow, or tool. It serves as a configuration parameter that controls parallelism and resource utilization. In software build systems, numjobs is commonly realized as a concurrency option, allowing multiple compilation tasks to proceed simultaneously to reduce total build time. For example, the GNU Make build tool uses the -j option to specify the number of jobs; setting a high value increases parallelism but also memory and I/O demands.

In task orchestration and data processing, numjobs is used to cap the number of worker processes or threads that can operate at once. This helps balance CPU usage with disk I/O and network traffic, and can prevent contention in shared environments or on machines with many users. Workflow managers, batch schedulers, and data pipelines often provide parallelism controls analogous to numjobs, sometimes labeled max_parallelism, concurrency_limit, or workers.

Practical guidance: selecting an appropriate numjobs depends on hardware and workload. A higher value can shorten compute time on CPU-bound tasks but may degrade performance for I/O-bound tasks or cause memory pressure. Testing with incremental increases and monitoring resource utilization is advisable.

See also: parallel processing, concurrency control, multi-threading, multiprocessing, GNU Make -j, worker pools, batch processing.