mm/damon/api: introduce DAMON_FILTER_TYPE_PGIDLE_SET

Patch series "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.


This patch (of 5):

DAMON_FILTER_TYPE_PGIDLE_UNSET matches only memory that was able to
confirm if it is marked as idle.  If the memory cannot be marked as idle,
it simply doesn't match.  Hence, finding memory that was marked as idle
with only DAMON_FILTER_TYPE_PGIDLE_UNSET is impossible.  Introduce a new
filter for the purpose, DAMON_FILTER_TYPE_PGIDLE_SET.

Link: https://lore.kernel.org/20260910142234.171562-1-sj@kernel.org
Link: https://lore.kernel.org/20260910142234.171562-2-sj@kernel.org
Signed-off-by: SJ Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: David Hildenbrand <david@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Liam R. Howlett <liam@infradead.org>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@kernel.org>

1 files changed, 2 insertions, 0 deletions

diff --git a/include/linux/damon.h b/include/linux/damon.h
index 871d26adf6ae..16800b3dc379 100644
--- a/include/linux/damon.h
+++ b/include/linux/damon.h
@@ -774,11 +774,13 @@ struct damon_prep {
  * @DAMON_FILTER_TYPE_ANON:		Anonymous pages.
  * @DAMON_FILTER_TYPE_MEMCG:		Specific memcg's pages.
  * @DAMON_FILTER_TYPE_PGIDLE_UNSET:	Pgidle is unset.
+ * @DAMON_FILTER_TYPE_PGIDLE_SET:	Pgidle is set.
  */
 enum damon_filter_type {
 	DAMON_FILTER_TYPE_ANON,
 	DAMON_FILTER_TYPE_MEMCG,
 	DAMON_FILTER_TYPE_PGIDLE_UNSET,
+	DAMON_FILTER_TYPE_PGIDLE_SET,
 };
 
 /**