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(-)
