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    Subject[PATCH 00/19 V2] mm: memcontrol: charge swapin pages on instantiation
    Date
    This patch series reworks memcg to charge swapin pages directly at
    swapin time, rather than at fault time, which may be much later, or
    not happen at all.

    Changes in version 2:
    - prevent double charges on pre-allocated hugepages in khugepaged
    - leave shmem swapcache when charging fails to avoid double IO (Joonsoo)
    - fix temporary accounting bug by switching rmap<->commit (Joonsoo)
    - fix double swap charge bug in cgroup1/cgroup2 code gating
    - simplify swapin error checking (Joonsoo)
    - mm: memcontrol: document the new swap control behavior (Alex)
    - review tags

    The delayed swapin charging scheme we have right now causes problems:

    - Alex's per-cgroup lru_lock patches rely on pages that have been
    isolated from the LRU to have a stable page->mem_cgroup; otherwise
    the lock may change underneath him. Swapcache pages are charged only
    after they are added to the LRU, and charging doesn't follow the LRU
    isolation protocol.

    - Joonsoo's anon workingset patches need a suitable LRU at the time
    the page enters the swap cache and displaces the non-resident
    info. But the correct LRU is only available after charging.

    - It's a containment hole / DoS vector. Users can trigger arbitrarily
    large swap readahead using MADV_WILLNEED. The memory is never
    charged unless somebody actually touches it.

    - It complicates the page->mem_cgroup stabilization rules

    In order to charge pages directly at swapin time, the memcg code base
    needs to be prepared, and several overdue cleanups become a necessity:

    To charge pages at swapin time, we need to always have cgroup
    ownership tracking of swap records. We also cannot rely on
    page->mapping to tell apart page types at charge time, because that's
    only set up during a page fault.

    To eliminate the page->mapping dependency, memcg needs to ditch its
    private page type counters (MEMCG_CACHE, MEMCG_RSS, NR_SHMEM) in favor
    of the generic vmstat counters and accounting sites, such as
    NR_FILE_PAGES, NR_ANON_MAPPED etc.

    To switch to generic vmstat counters, the charge sequence must be
    adjusted such that page->mem_cgroup is set up by the time these
    counters are modified.

    The series is structured as follows:

    1. Bug fixes
    2. Decoupling charging from rmap
    3. Swap controller integration into memcg
    4. Direct swapin charging

    Based on v5.7-rc3-mmots-2020-05-01-20-14.

    Documentation/admin-guide/cgroup-v1/memory.rst | 19 +-
    include/linux/memcontrol.h | 53 +--
    include/linux/mm.h | 4 +-
    include/linux/swap.h | 6 +-
    init/Kconfig | 17 +-
    kernel/events/uprobes.c | 10 +-
    mm/filemap.c | 43 +--
    mm/huge_memory.c | 13 +-
    mm/khugepaged.c | 29 +-
    mm/memcontrol.c | 449 +++++++----------------
    mm/memory.c | 51 +--
    mm/migrate.c | 20 +-
    mm/rmap.c | 53 +--
    mm/shmem.c | 108 +++---
    mm/swap_cgroup.c | 6 -
    mm/swap_state.c | 89 ++---
    mm/swapfile.c | 25 +-
    mm/userfaultfd.c | 5 +-
    18 files changed, 367 insertions(+), 633 deletions(-)

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