function create() {
    db.c.drop()
    db.createCollection('c', {capped:true, size:20*1024*1024*1024})
}

function insert() {

    x = ''
    for (var i=0; i<4000; i++)
        x += 'x'

    every = 10000
    for (var i=0; ; ) {
        var bulk = db.c.initializeUnorderedBulkOp();
        for (var j=0; j<every; j++, i++)
            bulk.insert({x:x});
        bulk.execute();
        //print(i)
    }
}