Date: Wed, 25 Oct 1995 06:17:07 -0700 From: "Jordan K. Hubbard" <jkh@time.cdrom.com> To: Gavin Lim <gavin@linux1.dlsu.edu.ph> Cc: hackers@freefall.FreeBSD.org Message-ID: <27312.814627027@time.cdrom.com> In-Reply-To: Your message of "Tue, 24 Oct 1995 19:22:56 PDT." <199510250226.TAA19363@freefall.freebsd.org>
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> In order to transfer a process, we have to save the process state, > probably save it to a file, and transfer this file to the destination > computer, where it would be deserialized and converted back to data > structures. When this is done, the process can resume execution on the > destination computer. Ah, my favorite axe to grind! :-) [ everyone else covers their eyes: "Oh no! Not this again!" :) ] Yes, you've stumbled onto one of the "hard problems" that a lot of UNIX vendors have simply punted on after examining it. It's not a trivial one and solving it will take a fairly fundamental re-think about how a process' "relationship" with the host computer is handled. The biggest bugaboo is the file table. Assuming that saving the process text, data and stack information is a problem you've solved (which would either require that we stop paging directly out of executables or that the relationship between process and executable became rather more abstract) you've still got to worry about all the files it has open and its controlling TTY. What happens when the image is reactivated on the other host? Do its file I/O requests to any now non-local files go back to the original host, do you assume a homogenous AFS-like file system for which all files have universal IDs, or what? The Sprite project's efforts to solve this problem ended up producing a system that didn't look much like UNIX anymore! In other words, I doubt that the people on this list are going to be able to help you all that much, at least not relative to our current code base. You have some substantial re-architecting ahead of you! Jordan
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