4 ms·

I think he was referring to the part where a calloc'd memory page will be zeroed the first time it's used, rather than all at once at the beginning. In a real-

• valarauca1 10y ago
  In a realtime system you can't use virtual memory because the access times are unpredictable.
  • wyldfire 10y ago
    I specifically avoided that word because it triggers particular deadlines that people have in mind. If my application requires no more than X ms latency I don't care to handwring over realtime vs soft realtime vs whatever, but it's still critical to fit in the budget. But indeed you can get reliable low-latency products to work on linux, with virtual memory. But like I said pinning is a great way to keep those peaks down.
    • valarauca1 10y ago
      The division you are looking for is Hard Realtime: Embedded system, no virtual memory/OS. Or special OS provisions to let them run. Soft Realtime: Responsive. In the case you are aiming for the second. There are several million things that'll net greater performance. We're talking about saving a matter of nano-seconds in C/C++. How you load your config will have more effect then this. If you want to save $1,000,000 rolling pennies a start. But there are likely way bigger savings elsewhere, worth way more time, and less effort.
      • karmakaze 10y ago
        I didn't think how it's achieved matters to the classification which is by the consequence of missing a deadline according to good ol' Wikipedia: Hard – missing a deadline is a total system failure. Firm – infrequent deadline misses are tolerable, but may degrade the system's quality of service. The usefulness of a result is zero after its deadline. Soft – the usefulness of a result degrades after its deadline, thereby degrading the system's quality of service
        • valarauca1 10y ago
          Your difference between soft/firm is an arbitrary decision made by a manager, not really a hard/fast If I can't meet this deadline my system is a total technical failure. You've created a false dichotomy.