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SubjectRe: Schedule idle
Rik van Riel writes:
> In my view, RT tasks really should have absolute
> priority over non-RT tasks and static priority
> within it's own class.

You know, what's sad about this continued debate about "RT" is
that there is a persistent failure to understand that
"real-time", as it is conventionally used, means "guaranteed
response time". It does not mean "ASAP scheduling" or "minimum
scheduling latency". There are inherent conflicts between
real-time and timesharing that are not easy, or maybe not even
possible, to resolve.

If Richard Gooch had taken the tack that the Linux scheduler had
undesirable latency when proposing his scheduler patches, I don't
think I or several other people would have objected. But when he
claimed that his patches would make Linux a better "real-time"
operating system, I did object, because you can't make a
real-time operating system out of a timesharing system just by
fiddling with the scheduler, or implementing "priority
inheritance", or doing other things that have been proposed.

Linux is a timesharing system, by design, and that assumption is
pervasive though things like interrupt handling and the driver
model. Anyone who thinks that Linux can be made into a real-time
system by fiddling with the scheduler and maybe a couple of other
things is deluding himself.

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