stream-clone: adjust default value for worker and memory Increasing the memory usage does not seems to yield much speed up, so we can restrict it more aggressively. However, unlimited memory usage can overwhelm a system and result in massive slowdown if the process start swapping. So it is still possible to configure it, but it is not longer used in any default profile. Having too many workers can slow things a bit, but not too much. So we can try to use higher default to yield benefit on large system.