mm/damon/core: introduce nr_accesses_bp

Add yet another representation of the access rate of each region, namely
nr_accesses_bp.  It is just same to the nr_accesses but represents the
value in basis point (1 in 10,000), and updated at once in every
aggregation interval.  That is, moving_accesses_bp is just nr_accesses *
10000.  This may seems useless at the moment.  However, it will be useful
for representing less than one nr_accesses value that will be needed to
make moving sum-based nr_accesses.

Link: https://lkml.kernel.org/r/20230915025251.72816-6-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Brendan Higgins <brendanhiggins@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

include/linux/damon.h

@@ -40,6 +40,7 @@ struct damon_addr_range {
  * @ar:			The address range of the region.
  * @sampling_addr:	Address of the sample for the next access check.
  * @nr_accesses:	Access frequency of this region.
+ * @nr_accesses_bp:	@nr_accesses in basis point (0.01%).
  * @list:		List head for siblings.
  * @age:		Age of this region.
  *
@@ -49,6 +50,9 @@ struct damon_addr_range {
  * not be done with direct access but with the helper function,
  * damon_update_region_access_rate().
  *
+ * @nr_accesses_bp is another representation of @nr_accesses in basis point
+ * (1 in 10,000) that updated every aggregation interval.
+ *
  * @age is initially zero, increased for each aggregation interval, and reset
  * to zero again if the access frequency is significantly changed.  If two
  * regions are merged into a new region, both @nr_accesses and @age of the new
@@ -58,6 +62,7 @@ struct damon_region {
 	struct damon_addr_range ar;
 	unsigned long sampling_addr;
 	unsigned int nr_accesses;
+	unsigned int nr_accesses_bp;
 	struct list_head list;
 
 	unsigned int age;