On Tue, Sep 26, 2023 at 12:49 PM Nhat Pham <nphamcs@xxxxxxxxx> wrote: > > Currently, hugetlb memory usage is not acounted for in the memory > controller, which could lead to memory overprotection for cgroups with > hugetlb-backed memory. This has been observed in our production system. > > This patch series rectifies this issue by charging the memcg when the > hugetlb folio is allocated, and uncharging when the folio is freed. In > addition, a new selftest is added to demonstrate and verify this new > behavior. > > Nhat Pham (2): > hugetlb: memcg: account hugetlb-backed memory in memory controller > selftests: add a selftest to verify hugetlb usage in memcg > > MAINTAINERS | 2 + > fs/hugetlbfs/inode.c | 2 +- > include/linux/hugetlb.h | 6 +- > include/linux/memcontrol.h | 8 + > mm/hugetlb.c | 23 +- > mm/memcontrol.c | 40 ++++ > tools/testing/selftests/cgroup/.gitignore | 1 + > tools/testing/selftests/cgroup/Makefile | 2 + > .../selftests/cgroup/test_hugetlb_memcg.c | 222 ++++++++++++++++++ > 9 files changed, 297 insertions(+), 9 deletions(-) > create mode 100644 tools/testing/selftests/cgroup/test_hugetlb_memcg.c > > -- > 2.34.1 > We've had this behavior at Google for a long time, and we're actually getting rid of it. hugetlb pages are a precious resource that should be accounted for separately. They are not just any memory, they are physically contiguous memory, charging them the same as any other region of the same size ended up not making sense, especially not for larger hugetlb page sizes. Additionally, if this behavior is changed just like that, there will be quite a few workloads that will break badly because they'll hit their limits immediately - imagine a container that uses 1G hugetlb pages to back something large (a database, a VM), and 'plain' memory for control processes. What do your workloads do? Is it not possible for you to account for hugetlb pages separately? Sure, it can be annoying to have to deal with 2 separate totals that you need to take into account, but again, hugetlb pages are a resource that is best dealt with separately. - Frank
