[linux-audio-dev] [Slightly OT] How to access "real-time" capabilities

This is, I know, slightly off-topic for this group, as it does not deal with audio per se. It does, however, deal with the "real-time"/preemptible Linux kernel, for which I think most of the expertice is gathered here. The OS is Linux, the computer an ordinary PC. The task we are faced with is to run a program, tcpreplay, in such a way that it delivers its network packets as precisely as possible. I.e. the packets should be delivered to the network with the smallest possible timing error. We think that the way to minimize this timing error is to use a kernel with the real-time patches, as this will improve latency and response times. The question is how we can assure that the program really utilizes the real-time capabilities of the kernel. My understanding is that having a real-time capable kernel is only the first step, the second necessary step is to get access to this capabilities? So, how does one accomplish this, given that the program itself does nothing to achieve this? * Will an ordinary program, run as root, take advantage of the real time capabilities of the kernel? * Will an ordinary program, run as a user that is a member of the "audio" group on f.i. Agnula, take advantage of the real-time capabilities? * If given a real-time kernel, what else is necessary to take advantage of its capabilities? * How does normal priorities (nice, renice) play together with the real-time kernel? With kind regards Asbjørn Sæbø