RE: Followup British Telecom outage reason
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; nanog@merit.edu 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.
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; nanog@merit.edu 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 joelja@darkwing.uoregon.edu Academic User Services consult@gladstone.uoregon.edu 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.
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:
and
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; nanog@merit.edu 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 joelja@darkwing.uoregon.edu Academic User Services consult@gladstone.uoregon.edu 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.
participants (3)
-
Joel Jaeggli -
Vadim Antonov -
Youse, Chuck