Unable to insert docs to a bucket created with 100M

Build : 7.0.0-3050
Note: Using Couchstore (not Magma)

Steps to reproduce :
1. Create a 1 node cluster with data service
2. Install any sample bucket.

Bucket would get created with 100MB bucket size, but the empty bucket uses 153MB RAM. Errors like the following get generated -
Hard out-of-memory error: Bucket "beer-sample" on node 127.0.0.1 is full. No memory currently allocated to this bucket can be easily released.

This is a regression. Last tested good build is 7.0.0-3043 (issue wasn't seen in this build). The following commit seems to be the cause -

• Commit: 38db2da4cb1feba00fd7c4a02c3c039e5dec952d in build: couchbase-server-7.0.0-3045
  MB-36572: Use CouchKVStoreFileCache

Full changelog between 7.0.0-3043 and 7.0.0-3050 :
http://172.23.123.43:10000/?product=couchbase-server&fromVersion=7.0.0&fromBuild=3043&toVersion=7.0.0&toBuild=3050&f_asterixdb=on&f_backup=on&f_build=on&f_cbas-core=on&f_cbbs=on&f_cbgt=on&f_couchbase-cli=on&f_couchstore=on&f_eventing=on&f_forestdb=on&f_goxdcr=on&f_indexing=on&f_kv_engine=on&f_magma=on&f_ns_server=on&f_query=on&f_testrunner=on&f_tlm=on