кривая иерархического добросовестного обслуживания (Hierarchical Fair Service Curve)
SEPARATE LS / RT SCs
Another difference from the original HFSC paper is that RT and LS
SCs can be specified separately. Moreover, leaf classes are
allowed to have only either RT SC or LS SC. For interior classes,
only LS SCs make sense: any RT SC will be ignored.
