The Swapper is optimized for loading and dumping bulk data. In SST it is often the case that messages contain only a few objects (for example, <100) and are less than 1KB in size. This characterization is particularly true of systems using by-reference marshaling as large data sets are often seen as mutable and so are passed by reference.

To take advantage of these properties, SST contains a lightweight marshaler (SstLightweightMarshaler) which does both by-value and by- reference marshaling. The Swapper and lightweight marshalers are largely interchangeable (although their output is not). They can also co-exist.

As the name implies, the lightweight marshaler is smaller and faster than Swapper marshaling for most use-cases encountered. Nonetheless, requirements vary from application to application; if one marshaler does not meet your needs, it is likely that the other will.