On 14.10.20 17:22, David Hildenbrand wrote: > Hi everybody, > > Michal Privoznik played with "free page reporting" in QEMU/virtio-balloon > with hugetlbfs and reported that this results in [1] > > 1. WARNING: CPU: 13 PID: 2438 at mm/page_counter.c:57 page_counter_uncharge+0x4b/0x5 > > 2. Any hugetlbfs allocations failing. (I assume because some accounting is wrong) > > > QEMU with free page hinting uses fallocate(FALLOC_FL_PUNCH_HOLE) > to discard pages that are reported as free by a VM. The reporting > granularity is in pageblock granularity. So when the guest reports > 2M chunks, we fallocate(FALLOC_FL_PUNCH_HOLE) one huge page in QEMU. > > I was also able to reproduce (also with virtio-mem, which similarly > uses fallocate(FALLOC_FL_PUNCH_HOLE)) on latest v5.9 > (and on v5.7.X from F32). > > Looks like something with fallocate(FALLOC_FL_PUNCH_HOLE) accounting > is broken with cgroups. I did *not* try without cgroups yet. > > Any ideas? Just tried without the hugetlb controller, seems to work just fine. I'd like to note that - The controller was not activated - I had to compile the hugetlb controller out to make it work. -- Thanks, David / dhildenb
