I considered that this could be the consequence of 8 tables periodically remapping in contention with each other. But I determined that the performance hit is significant even well below the point at which any of the tables would require a remap. And the performance hit is also not an issue of being memory constrained and therefor causing a lot more paging, since this is easily observable with 200+GB of free RAM and no disk activity. Furthermore than are no reads into these tables while marshalling, and all of the verification reads are under the (unchanged) sps performance measure.