On 04.02.20 09:40, Michael S. Tsirkin wrote: > 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. Will try to figure out how to best undo this mess :) > > >>>> >>>> (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? I can give it a shot. -- Thanks, David / dhildenb
