Hi. On Thursday 29 June 2006 08:44, Pavel Machek wrote: > Hi! > > > > > > So I don't really see the future of suspend2 because of this... > > > > > > > > But what Rafael and Pavel are doing is really only moving the highest > > > > level of controlling logic to userspace (ok, and maybe compression > > > > and encryption too). Everything important (freezing other processes, > > > > atomic copy and the guts of the I/O) is still done by the kernel. > > > > > > Can you do the same and move compression/encryption to userspace, too? > > > > > > And actually that "highest level" covers >50% of suspend2 code. That > > > would be around 7K lines of code removed from kernel if you did the > > > same, and suspend2 patch would be half the size... > > > > That's not true. The compression and encryption support add ~1000 lines, > > as you pointed out the other day. If I moved compression and encryption > > support to userspace, I'd remove 1000 lines and: > > > > - add more code for getting the pages copied to and from userspace > > No, if your main loop is already in userspace, you do not need to add > any more code. And you'd save way more than 1000 lines: > > * encryption/compression can be removed > > * but that means that writer plugins/filters can be removed > > * if you do compress/encrypt in userspace, you can remove that ugly > netlink thingie, and just display progress in userspace, too > > ...and then, image writing can be moved to userspace... > > * swapfile support > > * partition support > > * plus their plugin infrastructure. That's going way beyond your inital suggestion. And you haven't responded to the other points (which have instead been deleted). > > > > If we take the problem one step further, and begin to think about > > > > checkpointing, they're in even bigger trouble. I'll freely admit that > > > > I'd have to redesign the way I store data so that random parts of the > > > > image could be replaced, have hooks in mm to be able to learn what > > > > pages need have changed and would also need filesystem support to > > > > handle that part of the problem, but I'd at least be working in the > > > > right domain. > > > > > > Could you explain? I do not get the checkpointing remark. > > > > Sure. Suspending to disk is a pretty similar problem to checkpointing, > > except that you want to continue running afterwards, keep the image and > > modify it from time to time based on the changes in memory (having a > > checkpointing filesystem too, of course). My point is that modifying > > uswsusp to do checkpointing would be far harder precisely because you've > > pushed the highest level logic to userspace. It would be far more > > complicated, if not impossible for you to make the adjustments to do > > checkpointing. > > Aha, that's probably better done with Xen, anyway :-). Well, if you're going to put it in the too hard basket, it will have to be. Nigel -- See http://www.suspend2.net for Howtos, FAQs, mailing lists, wiki and bugzilla info.
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