By default, processes are bound to individual CPUs (either COREs or HWTHREADs, as defined by default or by user specification for the job). On nodes that are OVERSUBSCRIBEd (i.e., where the number of procs exceeds the number of assigned slots), the default is to not bind the processes.

Note

Processes from prior jobs that are already executing on a node are not “unbound” when a new job mapping results in the node becoming oversubscribed.

Binding is performed to the first available specified object type within the object where the process was mapped. In other words, binding can only be done to the mapped object or to a resource located beneath that object.

An object is considered completely consumed when the number of processes bound to it equals the number of CPUs within it. Unbound processes are not considered in this computation. Additional processes cannot be mapped to consumed objects unless the OVERLOAD qualifier is provided via the --bind-to command line option.

Note that directives and qualifiers are case-insensitive and can be shortened to the minimum number of characters to uniquely identify them. Thus, L1CACHE can be given as l1cache or simply as L1.

Supported binding directives include:

  • NONE does not bind the processes

  • HWTHREAD binds each process to a single hardware thread/ This requires that hwthreads be treated as independent CPUs (i.e., that either the HWTCPUS qualifier be provided to the map-by option or that hwthreads be designated as CPUs by default).

  • CORE binds each process to a single core. This can be done whether hwthreads or cores are being treated as independent CPUs provided that mapping is performed at the core or higher level.

  • L1CACHE binds each process to all the CPUs in an L1 cache.

  • L2CACHE binds each process to all the CPUs in an L2 cache

  • L3CACHE binds each process to all the CPUs in an L3 cache

  • NUMA binds each process to all the CPUs in a NUMA region

  • PACKAGE binds each process to all the CPUs in a PACKAGE

Any directive can include qualifiers by adding a colon (:) and any combination of one or more of the following to the --bind-to option:

  • OVERLOAD indicates that objects can have more processes bound to them than CPUs within them

  • IF-SUPPORTED indicates that the job should continue to be launched and executed even if binding cannot be performed as requested.

Note

Directives and qualifiers are case-insensitive. OVERLOAD is the same as overload.