Messages in this thread | | | Date | Sat, 22 Jun 2002 10:34:11 +0200 | From | Pavel Machek <> | Subject | Re: kernel upgrade on the fly |
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Hi!
> Nothing is impossible for anyone impervious to reason, and you might suprise > us (it'd make a heck of a graduate project). Hot migration isn't IMPOSSIBLE, > it's just a flipping pain in the ass. But the issue's a bit threadbare in > these parts (somewhere between "are we there yet mommy?" and "can I buy a > pony?").
Actually, getting a pony is easy compared to *this* ;-).
> The SANE answer always has been to just schedule some down time for the box. > The insane answer involves giving an awful lot of money to Sun or IBM or some > such for hot-pluggable backplanes. (How do you swap out THE BACKPLANE? > That's an answer nobody seems to have...)
You have two back backplanes and you use the other one during the switch?
> Clusters. Migrating tasks in the cluster, potentially similar problem. Look > at mosix and the NUMA stuff as well, if you're actually serious > about this. > You have to reduce a process to its vital data, once all the resources you > can peel away from it have been peeled away, swapped out, freed, etc. If you > can suspend and save an individual running process to a disk image (just a > file in the filesystem), in such a way that it can be individually re-loaded > later (by the same kernel), you're halfway there. No, it's not as easy as it > sounds. :)
Actually, if you can select few "important" processes, and only care about them, it can be done from userspace. Martin Mares did something like that, involving ptrace() and lots of limitations.
> > I can see the advantage of such a thing when a server can have the kernel > > upgraded (major or minor upgrade) without disrupting the ongoing services > > (ok, maybe a small few-seconds delay). Another instance would be to > > switch between different kernels in the /boot/ directory (for testing > > purposes, etc.) without rebooting the machine. > > See "belling the cat". Yeah, it's a great idea. The implementation's the > tricky bit.
My dictionary is too weak for this. Pavel -- (about SSSCA) "I don't say this lightly. However, I really think that the U.S. no longer is classifiable as a democracy, but rather as a plutocracy." --hpa - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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