On Fri, Feb 21, 2020 at 2:04 AM Rafael J. Wysocki <rafael@xxxxxxxxxx> wrote: > > My understanding of the problem is that the size of swap is > (theoretically) sufficient, but it is not used as expected during the > preallocation of image memory. Right. I have no idea how locality of pages is determined in the swap device. But if it's sufficiently fragmented such that contiguous free space for a hibernation image is not sufficient, then hibernation could fail. > It was stated in one of the previous messages (not in this thread, > cannot find it now) that swap (of the same size as RAM) was activated > (swapon) right before hibernation, so theoretically that should be > sufficient AFAICS. I mentioned it as an idea floated by systemd developers. I'm not sure if it's mentioned elsewhere. Some folks wonder if such functionality could be prone to racing. https://lore.kernel.org/linux-mm/CAJCQCtSx0FOX7q0p=9XgDLJ6O0+hF_vc-wU4KL=c9xoSGGkstA@xxxxxxxxxxxxxx/T/#m4d47d127da493f998b232d42d81621335358aee1 Another idea that's been suggested for a while is formally separating hibernation and paging into separate files (or partitions). a. Guarantees hibernation image has the necessary contiguous free space. b. Might be easier to create (or even obviate) a sane interface for hibernation images in swapfiles; that is, if it were a dedicated hibernationfile rather than being inserted in a swapfile. Right now that interface doesn't exist, so e.g. on Btrfs while it can support swapfiles and hibernation images, the offset has to be figured out manually so resume can succeed. https://github.com/systemd/systemd/issues/11939#issuecomment-471684411 -- Chris Murphy
