Part on STARPU_MIN/MAX_WORKERSIZE added in the manual.

doc/chapters/advanced-examples.texi

@@ -787,6 +787,15 @@ topology (NUMA node, socket, cache, ...) a combined worker will be created. If
 some nodes of the hierarchy have a big arity (e.g. many cores in a socket
 without a hierarchy of shared caches), StarPU will create combined workers of
 intermediate sizes.
+The user can give some hints to StarPU about combined workers sizes to favor.
+This can be done by using the environment variables STARPU_MIN_WORKERSIZE and
+STARPU_MAX_WORKERSIZE. When set, they will force StarPU to create the biggest
+combined workers possible without overstepping the defined boundaries.
+However, StarPU will create the remaining combined workers without abiding by
+the rules if not possible.
+For example : if the user specify a minimum and maximum combined workers size
+of 3 on a machine containing 8 CPUs, StarPU will create a combined worker of
+size 2 beside the combined workers of size 3.
 
 @subsection Concurrent parallel tasks