[RFC PATCH 05/19] mm/damon/core: introduce damon_region->probe_hits

[SeongJae Park <sj@kernel.org>]

Add an array for the per-region per-probe positive samples count.  For
simple and efficient implementation, add a limit to the number of data
probes and set the array to support only the limited number of counters.

Signed-off-by: SeongJae Park <sj@kernel.org>
---
 include/linux/damon.h | 4 ++++
 mm/damon/core.c       | 3 +++
 2 files changed, 7 insertions(+)

diff --git a/include/linux/damon.h b/include/linux/damon.h
index 3290792eab547..766d6daa52a3e 100644
--- a/include/linux/damon.h
+++ b/include/linux/damon.h
@@ -16,6 +16,8 @@
 
 /* Minimal region size.  Every damon_region is aligned by this. */
 #define DAMON_MIN_REGION_SZ	PAGE_SIZE
+/* Maximum number of monitoring probes. */
+#define DAMON_MAX_PROBES	(4)
 /* Max priority score for DAMON-based operation schemes */
 #define DAMOS_MAX_SCORE		(99)
 
@@ -52,6 +54,7 @@ struct damon_size_range {
  * @nr_accesses:	Access frequency of this region.
  * @nr_accesses_bp:	@nr_accesses in basis point (0.01%) that updated for
  *			each sampling interval.
+ * @probe_hits:		Number of probe-positive region samples.
  * @list:		List head for siblings.
  * @age:		Age of this region.
  *
@@ -80,6 +83,7 @@ struct damon_region {
 	unsigned long sampling_addr;
 	unsigned int nr_accesses;
 	unsigned int nr_accesses_bp;
+	unsigned char probe_hits[DAMON_MAX_PROBES];
 	struct list_head list;
 
 	unsigned int age;
diff --git a/mm/damon/core.c b/mm/damon/core.c
index 2ab1d6dd47da4..d4779b647a495 100644
--- a/mm/damon/core.c
+++ b/mm/damon/core.c
@@ -225,6 +225,7 @@ static void damon_verify_new_region(unsigned long start, unsigned long end)
 struct damon_region *damon_new_region(unsigned long start, unsigned long end)
 {
 	struct damon_region *region;
+	int i;
 
 	damon_verify_new_region(start, end);
 	region = kmem_cache_alloc(damon_region_cache, GFP_KERNEL);
@@ -235,6 +236,8 @@ struct damon_region *damon_new_region(unsigned long start, unsigned long end)
 	region->ar.end = end;
 	region->nr_accesses = 0;
 	region->nr_accesses_bp = 0;
+	for (i = 0; i < DAMON_MAX_PROBES; i++)
+		region->probe_hits[i] = 0;
 	INIT_LIST_HEAD(&region->list);
 
 	region->age = 0;
-- 
2.47.3