Plasma memory usage changes depending on kv ops rate

Observed that plasma memory usage changes depending on kv ops rate in incremental phase.
e.g.Test- 250M docs
with 50k ops, uses 60559MB- http://perf.jenkins.couchbase.com/job/secondary-plasma-dev/100/
with 100k ops, uses 72528MB- http://perf.jenkins.couchbase.com/job/secondary-plasma/624/

With 100k ops rate there are more number of splits and more number of pages.

Here is cbmonitor comparison for both runs- http://cbmonitor.sc.couchbase.com/reports/html/?snapshot=nyx_500-2759_build_incrindex_5059&snapshot=nyx_500-2759_build_incrindex_afbd#nyx_500-2759_build_incrindex_5059nyx_500-2759_build_incrindex_afbdnyx_500-2759_build_incrindex_5059nyx_500-2759_build_incrindex_afbdmemory_used_storage