[...] >> >> Issue 2: When called via the shrinker, (but also to fix Issue 1), it could be >> that we do have VIRTIO_BALLOON_F_MUST_TELL_HOST. I assume this means >> (-ENOCLUE) that we have to wait until the hypervisor notifies us via the STOP? Or >> for which event do we have to wait? Because there is no way to *tell host* here >> that we want to reuse a page. The hypervisor will *tell us* when we can reuse pages. >> For the shrinker it is simple: Don't use the shrinker with >> VIRTIO_BALLOON_F_MUST_TELL_HOST :) . But to fix Issue 1, we *would* have to wait >> until we get a STOP signal. That is not really possible because it might >> take an infinite amount of time. >> >> Michael, any clue on which event we have to wait with >> VIRTIO_BALLOON_F_MUST_TELL_HOST? IMHO, I don't think >> VIRTIO_BALLOON_F_MUST_TELL_HOST applies to VIRTIO_BALLOON_F_FREE_PAGE_HINT and >> we'd better document that. It introduces complexity with no clear benefit. > > I meant that we must wait for host to see the hint. Signalled via using > the buffer. But maybe that's too far in the meaning from > VIRTIO_BALLOON_F_MUST_TELL_HOST and we need a separate new flag for Yes, that's what I think. > that. Then current code won't be broken (yay!) but we need to > document another flag that's pretty similar. I mean, do we need a flag at all as long as there is no user? Introducing a flag and documenting it if nobody uses it does not sound like a work I will enjoy :) We can simply document "VIRTIO_BALLOON_F_MUST_TELL_HOST does not apply to FREE_PAGE_HINTING" and "with FREE_PAGE_HINTING, the guest can reuse pages any time, without waiting for a response/ack from the hypervisor". Thoughts? -- Thanks, David / dhildenb
