The Free On-line Dictionary of Computing (30 December 2018):

granularity
coarse grain
fine grain
grain

    The size of the units of code under
   consideration in some context.  The term generally refers to
   the level of detail at which code is considered, e.g. "You can
   specify the granularity for this profiling tool".

   The most common computing use is in parallelism or concurrency
   where "fine grain parallelism" means individual tasks are
   relatively small in terms of code size and execution time, "coarse
   grain" is the opposite.  You talk about the "granularity" of the
   parallelism.

   The smaller the granularity, the greater the potential for
   parallelism and hence speed-up but the greater the overheads
   of synchronisation and communication.

   (1997-05-08)