5 ms·

Surely the ordinary regular tick would use exactly the same hardware to get the regular tick interrupt as the tickless one would use to get an irregular preempt

• gizmo686 14y ago
  I think the issue is that you don't necessarily know when you need to preempt before hand. For example, if you are a normal computer idling, in theory you do not need to do anything until something happens. However, you need to constantly check to see if anything happened, and the process of checking is doing something. With hardware support, you can skip checking when nothing happened.
  • adestefan 14y ago
    This allows for better power management since the hardware has a better understanding the state of the system. When a system is idle now the hardware is also idle and can put itself to sleep.
  • to3m 13y ago
    You don't know when to preempt - but that's what the timer is for. It would be something of an emergency measure, because most of the time, most threads go to sleep for some other reason than running out of time. (Of course, if a thread regularly exceeds its time slice, the computer won't go into an idle state - but that's the right thing for it to do, because it isn't idle.) As for checking for something happening, do you need to poll for this? I don't think it's necessary in the general case. Perhaps there is some broken hardware that doesn't support interrupts, but I have a hard time believing that's very common. Aside from that, nothing ever happens except by request, and (if structured right - not that I'm suggesting this is automatically easy) polling is unnecessary.