mm/damon: introduce pgidle_set probe filter type

Users can do effective access monitoring with DAMON, using set_pgidle probe prep operation and pgidle_unset allowing probe filter. In the setup, high probe_hits means the region was accessed frequently. Zero probe_hits means the region was not accessed. The filter, however, matches only the memory that can show the idleness. Regions of zero probe_hits may contain memory that was just unable to show the idleness. On virtual address space based monitoring, for example, non-present pages are reported as cold. It is truly cold, but if the purpose is to make some operations like reclaiming or compressing the data, this is not really useful. Introduce a new probe filter type, pgidle_set, that confirms the page is marked as idle. Using it instead of pgidle_unset, users can find cold pages that can effectively be processed.

Patch 1 introduces the pgidle_set probe filter type to DAMON kernel API. Patches 2 and 3 add support for it on physical and virtual address space operation sets, respectively. Patch 4 adds support for it on the DAMON sysfs interface. Finally, patch 5 updates the documentation for the new filter type.

Changes from RFC v1.1
- RFC v1.1: https://lore.kernel.org/[email protected]
- Drop RFC tag.
Changes from RFC
- RFC: https://lore.kernel.org/[email protected]
- Rebase to latest mm-new.

SJ Park (5):
mm/damon/api: introduce DAMON_FILTER_TYPE_PGIDLE_SET mm/damon/paddr: support DAMON_FILTER_TYPE_PGIDLE_SET mm/damon/vaddr: support DAMON_FILTER_TYPE_PGIDLE_SET mm/damon/sysfs: support DAMON_FILTER_TYPE_PGIDLE_SET Docs/mm/damon/design: update for pgidle_set probe filter

 Documentation/mm/damon/design.rst | 3 ++-
 include/linux/damon.h             | 2 ++
 mm/damon/paddr.c                  | 6 ++++++
 mm/damon/sysfs.c                  | 4 ++++
 mm/damon/vaddr.c                  | 7 +++++++
 5 files changed, 21 insertions(+), 1 deletion(-)

base-commit: db0399c7f55d733a66e5661c4300276629123b0b

2.47.3