Linked by David Adams on Fri 18th Apr 2008 17:34 UTC, submitted by Rahul
Linux Lennart Poettering of Red Hat, PulseAudio maintainer has blogged in detail about the impact of Real-Time Group scheduling in 2.6.25 kernel. The Real time patches come from -rt patchset maintained by Ingo Molnar of Red Hat which aims to make Linux the first general purpose operating system with hard real time features.
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'hard' real time is not so well defined as you might imagine.

A truly deterministic implementation cannot have such niceties as processor cache, interrupts or file i/o as you cannot accurately predict their latencies.

A practical 'hard' real time system still has to allow for missed deadlines, or have some kind of priority assignment for real time threads. This opens up the possibility of priority inversion. (see Mars Rover Pathfinder.)

So there are always compromises and each implementation is specific. The Linux RT patches provide one implementation, with all the problems associated with running on commodity hardware, networking, file io etc. Whether it fits your needs is another matter.

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