Date: Tue, 14 Feb 2012 19:35:03 -0600 From: Jim Bryant <kc5vdj.freebsd@gmail.com> To: Julian Elischer <julian@freebsd.org> Cc: Maninya M <maninya@gmail.com>, freebsd-hackers@freebsd.org Subject: Re: OS support for fault tolerance Message-ID: <4F3B0BC7.4010804@gmail.com> In-Reply-To: <4F3A9266.9050905@freebsd.org> References: <CAC46K3mc=V=oBOQnvEp9iMTyNXKD1Ki_%2BD0Akm8PM7rdJwDF8g@mail.gmail.com> <4F3A9266.9050905@freebsd.org>
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Mirrored SMP? Even NonStops require a supervisory CPU subsystem to manage what is working or not. SMP itself would have to be totally rethought. My suggestion is to study the examples of NonStop and Guardian-90. Julian Elischer wrote: > On 2/14/12 6:23 AM, Maninya M wrote: >> For multicore desktop computers, suppose one of the cores fails, the >> FreeBSD OS crashes. My question is about how I can make the OS tolerate >> this hardware fault. >> The strategy is to checkpoint the state of each core at specific >> intervals >> of time in main memory. Once a core fails, its previous state is >> retrieved >> from the main memory, and the processes that were running on it are >> rescheduled on the remaining cores. >> >> I read that the OS tolerates faults in large servers. I need to make >> it do >> this for a Desktop OS. I assume I would have to change the scheduler >> program. I am using FreeBSD 9.0 on an Intel core i5 quad core machine. >> How do I go about doing this? What exactly do I need to save for the >> "state" of the core? What else do I need to know? >> I have absolutely no experience with kernel programming or with FreeBSD. >> Any pointers to good sources about modifying the source-code of FreeBSD >> would be greatly appreciated. > This question has always intrigued me, because I'm always amazed > that people actually try. > From my viewpoint, There's really not much you can do if the core > that is currently holding the scheduler lock fails. > And what do you mean by 'fails"? do you run constant diagnostics? > how do you tell when it is failed? It'd be hard to detect that 'multiply' > has suddenly started giving bad results now and then. > > if it just "stops" then you might be able to have a watchdog that > notices, but what do you do when it was half way through rearranging > a list of items? First, you have to find out that it held > the lock for the module and then you have to find out what it had > done and clean up the mess. > > This requires rewriting many many parts of the kernel to remove > 'transient inconsistent states". and even then, what do you do if it > was half way through manipulating some hardware.. > > and when you've figured that all out, how do you cope with the > mess it made because it was dying? > Say for example it had started calculating bad memory offsets > before writing out some stuff and written data out over random memory? > > but I'm interested in any answers people may have > >> _______________________________________________ >> freebsd-hackers@freebsd.org mailing list >> http://lists.freebsd.org/mailman/listinfo/freebsd-hackers >> To unsubscribe, send any mail to >> "freebsd-hackers-unsubscribe@freebsd.org" >> > > _______________________________________________ > freebsd-hackers@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-hackers > To unsubscribe, send any mail to > "freebsd-hackers-unsubscribe@freebsd.org" > . >
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