Messages in this thread | | | Date | Wed, 21 Jan 1998 13:07:45 +0000 | From | Richard Jones <> | Subject | Re: Hot swap kernel |
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Kalle Andersson wrote: > > Evening all > > I am sorry if I am the 57th asking for this but it would be great to be able to > hotswap kernels, ie change kernel without needing to reboot. [...]
A very nice idea, but quite hard to implement. The problem is that _all_ the data stored by the kernel needs to be transfered to the new kernel. That is, all the static variables used everywhere, page tables, process table, file system mount information and god knows what (possibly outstanding NFS request information :-), ... Then, of course, the new kernel has probably changed the semantics of particular variables or changed the format of particular data structures, so you need to ``upgrade'' the state to the new kernel. And, of course, you need different upgrade modules for different kernel transitions. Imagine the difficulties of upgrading the state from 1.2.13 -> 2.1.80! (You can also do it in stages, by chaining together 1.2.13->2.0->2.1 as a _very_ simplified example).
Yuk. Monolithic kernels just don't support this very well. It might be a lot easier with a microkernel, since the amount of state you need to deal with is reduced.
Rich.
-- Richard Jones rjones@orchestream.com Tel: +44 171 460 6141 Fax: .. 4461 Orchestream Ltd. 262a Fulham Rd. London SW10 9EL. "you'll write in PGP: www.four11.com telegraphic, or you won't write at all" [Céline] Copyright © 1998 Richard W.M. Jones
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