I was playing with merge throttling and discovered that our
SimpleRateLimiter is throttling far more than requested; e.g. I asked
for 50 MB/sec merge throttling, but it throttled at more like 8
The problem is we are calling Thread.sleep on too-small (< 1 msec)
times; on ordinary (non-real-time) JVMs, anything less than 1 msec is
rounded up to 1 msec. Also, System.nanoTime() is somewhat costly.
To fix this, I think we should aggregate the incoming byte count,
until it crosses a threshold of enough bytes to warrant pausing.