[PATCH mm-new v3 0/2] mm: zswap: add per-memcg stat for incompressible pages

[Jiayuan Chen <jiayuan.chen@linux.dev>]

In containerized environments, knowing which cgroup is contributing
incompressible pages to zswap is essential for effective resource
management. This series adds a new per-memcg stat 'zswap_incomp' to
track incompressible pages, along with a selftest.

Patch 1: Add the per-memcg zswap_incomp stat and documentation
Patch 2: Add selftest for the new stat

Changes v2 -> v3:
https://lore.kernel.org/linux-mm/20260206072220.144008-1-jiayuan.chen@linux.dev/

- Remove inline comments for incompressibility check (Yosry Ahmed)
- Use PAGE_SIZE instead of hardcoded 4096 in selftest (SeongJae Park)
- Use pipe for parent-child synchronization instead of usleep
  (JP Kobryn, SeongJae Park)
- Use MADV_PAGEOUT instead of memory.reclaim to push pages into zswap,
  and use mmap instead of malloc accordingly (Nhat Pham)
- Collect Reviewed-by and Acked-by tags

Changes v1 -> v2:
https://lore.kernel.org/linux-mm/20260205053013.25134-1-jiayuan.chen@linux.dev/

- Rename zswpraw/MEMCG_ZSWAP_RAW to zswap_incomp/MEMCG_ZSWAP_INCOMP
  (Shakeel Butt, Yosry Ahmed)
- Drop zswap_is_incomp() helper, keep opencode (size == PAGE_SIZE) with
  comments explaining the incompressibility check (Yosry Ahmed)
- Add documentation in cgroup-v2.rst (Nhat Pham, SeongJae Park)
- Add selftest as a separate patch (Nhat Pham)
- Add reference link to Chris Li's discussion on the need for per-memcg
  incompressible page tracking (Nhat Pham)

Jiayuan Chen (2):
  mm: zswap: add per-memcg stat for incompressible pages
  selftests/cgroup: add test for zswap incompressible pages

 Documentation/admin-guide/cgroup-v2.rst     |   5 +
 include/linux/memcontrol.h                  |   1 +
 mm/memcontrol.c                             |   6 +
 tools/testing/selftests/cgroup/test_zswap.c | 136 ++++++++++++++++++++
 4 files changed, 148 insertions(+)

-- 
2.43.0