Test creates 15k collections as fast as possible. 4.0.10 is on the left, 4.2.0-rc1 on the right.

• 4.0.10 (B-E)
  • overall creating about 150 collections per second
  • C-D: rate slows down during checkpoint, but no stalls
• 4.2.0-rc1 (F-J)
  • F-G: initial rate is higher
  • G: after a few seconds collection creation rate drops to ~3/s, accompanined by a high rate of failed evictions and an extremely high rate of bytes written, ~200 MB/s.
  • H: shortly after the checkpoint starts we see an extended stall of ~100 s, during which no FTDC data is collected.
  • I: stall ends, but checkpoint continues and very low rate of collection creation and very high rate of bytes written continues (possibly indefinitely?).

function repro() {
    nthreads = 10
    threads = []
    for (var t=0; t<nthreads; t++) {
        thread = new ScopedThread(function(t) {
            for (var i=0; i<1500; i++) {
                if (t==0 && i%100==0)
                    print(i)
                db['c' + t + '.' + i].insert({})
            }
        }, t)
        threads.push(thread)
        thread.start()
    }
    for (var t = 0; t < nthreads; t++)
        threads[t].join()
}