code: func (fc *DocumentsWriterFlushControl) assertNumDocsSinceStalled(stalled bool) {
  	if fc.stalled {
  		fc.numDocsSinceStalled++
  	} else {
  		fc.numDocsSinceStalled = 0
  	}
  }
docs: /*
  updates the number of documents "finished" while we are in a stalled
  state. this is important for asserting memory upper bounds since it
  corresponds to the number of threads that are in-flight and crossed
  the stall control check before we actually stalled.
  */