4 ms·

Because you don't want the system to break.

• derefr 11y ago
  But it wouldn't, because the surrounding infrastructure would be guaranteeing that. My point is that distributed systems engineers are assuming too few things about the hardware and OS. A much wider space of distributed algorithms become useful if you have full control over your stack. Do you think NASA quibbles about how to make a perfect consensus bit-coding algorithm between the fault-tolerant processors of a mars probe? No; they just use hardware+firmware that provides a hard real-time platform, allowing the algorithm itself to be simple.
  • baruch 11y ago
    It doesn't require a VM pause to cause a system freeze, an SMI interrupt can do that as well. It doesn't take a lot to have backwards time travel, NTP can do that for you as well in some bad configurations. It's very hard to rely on time in a distributed system. If you want a simple algorithm just don't rely on time at all, use it for logs so a human can correlate things when debugging an issue but don't assume time will flow at the same rate for all systems. Do use a monotonic clock always for internal timers, time does move backwards in systems.
    • ahoka 11y ago
      I have seen SMI pauses for almost 5 seconds!