On Tue, Feb 04, 2020 at 09:35:21AM +0100, David Hildenbrand wrote: > >>> I would say reverting probably makes sense. I'm not sure there is much > >>> value to having a shrinker running deflation when you are actively trying > >>> to increase the balloon. It would make more sense to wait until you are > >>> actually about to start hitting oom. > >> > >> I think the shrinker makes sense for free page hinting feature > >> (everything on free_page_list). > >> > >> So instead of only reverting, I think we should split it up and always > >> register the shrinker for VIRTIO_BALLOON_F_FREE_PAGE_HINT and the OOM > >> notifier (as before) for VIRTIO_BALLOON_F_MUST_TELL_HOST. > > s/VIRTIO_BALLOON_F_MUST_TELL_HOST/VIRTIO_BALLOON_F_DEFLATE_ON_OOM/ > > :) Well VIRTIO_BALLOON_F_MUST_TELL_HOST is also broken by shrinker with VIRTIO_BALLOON_F_FREE_PAGE_HINT as that code adds buffers but does not wait for them to be used even with VIRTIO_BALLOON_F_MUST_TELL_HOST. We never noticed because QEMU does not advertize VIRTIO_BALLOON_F_MUST_TELL_HOST. > >> > >> (Of course, adapting what is being done in the shrinker and in the OOM > >> notifier) > > > > David, > > > > Please keep me posted. I decided to adapt the same solution as the virtio > > balloon for the VMware balloon. If the verdict is that this is damaging and > > the OOM notifier should be used instead, I will submit patches to move to > > OOM notifier as well. > > Will do. It all sounds sub-optimal to me at this point ... but I prefer > the old variant where a simple "drop_slab()" won't deflate the balloon. > That looks broken to me. Okay. Could you post a patch? > -- > Thanks, > > David / dhildenb
