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North American Network Operators Group Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical RE: Followup British Telecom outage reason
Realtime stuff is not only about process rescheduling times. The definition of real-time system is: a system which can guarantee execution of tasks within specified time limits. I've seen a real-life real-time system with guaranteed reaction time of two hours (it was controlling irrigation water gates). For routers, the "real-time" limits one needs is in 0.1 second-range; making a system like that from a general-purpose OS is certainly doable. --vadim On Thu, 29 Nov 2001, Joel Jaeggli wrote: > > Um... The rtl kerenel runs the linux kernel as a pre-ementible low > priority thread, has proveable worst case timing around 15uSec between > assertion of interrupt and execution of the realtime handler, and is > posix compliant. > > visit: > > http://www.rtlinux.org/ > > and > > http://www.fsmlabs.com/ > > > > > On Thu, 29 Nov 2001, Youse, Chuck wrote: > > > > > You'll forgive me for being cynical here, but I seriously doubt that any > > Linux-derived operating systems could truly qualify as 'real-time'. To meet > > the requirements for an RTOS, Linux would have to be so heavily mutated that > > it would no longer be Linux. > > > > Cheers > > Chuck > > > > -----Original Message----- > > From: Patrick Greenwell > > To: Christian Kuhtz > > Cc: Alex Bligh; Paul Vixie; [email protected] > > Sent: 29/11/01 07:49 > > Subject: RE: Followup British Telecom outage reason > > > > > > On Wed, 28 Nov 2001, Christian Kuhtz wrote: > > > > > > > > > I guess some time someone will realize routers are both > > > > hardware, and software, and shock horror both, if done > > > > well, can actually add value. [hint & example: compare the > > > > scheduler on, say, Linux/FreeBSD, Windows 95 (sic), > > > > and your favourite router OS (*); pay particular attention > > > > to suitability for running realtime, or near realtime tasks, > > > > where such tasks may occasionally crash or overrun their > > > > expected timeslice; note how the best OS amongst the > > > > bunch for this aint exactly great]. > > > > > > > > (*) results may vary according to personal choice here. > > > > > > Don't use a non-realtime OS for something that you expect realtime or > > > near-realtime OS functionality. There are specific systems to address > > these > > > kinds of needs with rather complicated scheduling mechanism to > > accomodate > > > such requirements in a sensible manner. > > > > > > Is IOS a realtime operating system? No. Are any of the other listed > > OS > > > realtime operating systems? No. > > > > Actually there are multiple Linux-based RTOSes. > > > > -- > -------------------------------------------------------------------------- > Joel Jaeggli [email protected] > Academic User Services [email protected] > PGP Key Fingerprint: 1DE9 8FCA 51FB 4195 B42A 9C32 A30D 121E > -------------------------------------------------------------------------- > It is clear that the arm of criticism cannot replace the criticism of > arms. Karl Marx -- Introduction to the critique of Hegel's Philosophy of > the right, 1843. > >
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