Translations:Julia/35/en

Configuring Julia's threading behaviour

You can restrict the number of threads Julia can use by setting JULIA_NUM_THREADS=k, for example a single process on a 12 cpus-per-task job could use k=12. Setting the number of threads to the number of processors is a typical choice (although see Scalability for a discussion). In addition, one can 'pin' threads to cores, by setting JULIA_EXCLUSIVE to anything non-zero. As per the documentation, this takes control of thread scheduling away from the OS, and pins threads to cores (sometimes referred to 'green' threads with affinity). Depending on the computation that threads execute, this can improve performance when one has precise information on cache access patterns or otherwise unwelcome scheduling patterns used by the OS. Setting JULIA_EXCLUSIVE works only if your job has exclusive access to the compute nodes (all available CPU cores were allocated to your job). Since SLURM already pins processes and threads to CPU cores, asking Julia to re-pin threads may not lead to any performance improvement.