> // Fresh start shows the mongo process using 27MB of resident mem.
> result = {};
{ }
> result2 = {};
{ }
> for (i=0;i<640000;i++) {
...     result[i] = i * 3 % i;
...     result2[i] = result + 'aaaaaaaaaaaaaaaaaaaaaaaaa';
...     db.isMaster()
... }
{ "ismaster" : true, "maxBsonObjectSize" : 16777216, "ok" : 1 }
> // At this point, the process is holding on to 268mb of resident mem
> result = 0
0
> result2 = 0
0
> i = 0
0
> gc()
> // At this point, the process is holding onto 186mb of resident mem