[RFC 6/8] mm/damon/sysfs-schemes: support DAMOS apply interval

[SeongJae Park <sj@kernel.org>]

Update DAMON sysfs interval to support DAMOS apply intervals.  Users
can set and get the interval for each scheme in microseconds by writing
to and reading from the new sysfs file, 'apply_interval_us', in each
scheme sysfs directory.

Signed-off-by: SeongJae Park <sj@kernel.org>
---
 mm/damon/sysfs-schemes.c | 38 ++++++++++++++++++++++++++++++++++----
 1 file changed, 34 insertions(+), 4 deletions(-)

diff --git a/mm/damon/sysfs-schemes.c b/mm/damon/sysfs-schemes.c
index 3d30e85596b0..a7d70b95c4dd 100644
--- a/mm/damon/sysfs-schemes.c
+++ b/mm/damon/sysfs-schemes.c
@@ -1121,6 +1121,7 @@ struct damon_sysfs_scheme {
 	struct kobject kobj;
 	enum damos_action action;
 	struct damon_sysfs_access_pattern *access_pattern;
+	unsigned long apply_interval_us;
 	struct damon_sysfs_quotas *quotas;
 	struct damon_sysfs_watermarks *watermarks;
 	struct damon_sysfs_scheme_filters *filters;
@@ -1141,7 +1142,7 @@ static const char * const damon_sysfs_damos_action_strs[] = {
 };
 
 static struct damon_sysfs_scheme *damon_sysfs_scheme_alloc(
-		enum damos_action action)
+		enum damos_action action, unsigned long apply_interval_us)
 {
 	struct damon_sysfs_scheme *scheme = kmalloc(sizeof(*scheme),
 				GFP_KERNEL);
@@ -1150,6 +1151,7 @@ static struct damon_sysfs_scheme *damon_sysfs_scheme_alloc(
 		return NULL;
 	scheme->kobj = (struct kobject){};
 	scheme->action = action;
+	scheme->apply_interval_us = apply_interval_us;
 	return scheme;
 }
 
@@ -1353,6 +1355,25 @@ static ssize_t action_store(struct kobject *kobj, struct kobj_attribute *attr,
 	return -EINVAL;
 }
 
+static ssize_t apply_interval_us_show(struct kobject *kobj,
+		struct kobj_attribute *attr, char *buf)
+{
+	struct damon_sysfs_scheme *scheme = container_of(kobj,
+			struct damon_sysfs_scheme, kobj);
+
+	return sysfs_emit(buf, "%lu\n", scheme->apply_interval_us);
+}
+
+static ssize_t apply_interval_us_store(struct kobject *kobj,
+		struct kobj_attribute *attr, const char *buf, size_t count)
+{
+	struct damon_sysfs_scheme *scheme = container_of(kobj,
+			struct damon_sysfs_scheme, kobj);
+	int err = kstrtoul(buf, 0, &scheme->apply_interval_us);
+
+	return err ? err : count;
+}
+
 static void damon_sysfs_scheme_release(struct kobject *kobj)
 {
 	kfree(container_of(kobj, struct damon_sysfs_scheme, kobj));
@@ -1361,8 +1382,12 @@ static void damon_sysfs_scheme_release(struct kobject *kobj)
 static struct kobj_attribute damon_sysfs_scheme_action_attr =
 		__ATTR_RW_MODE(action, 0600);
 
+static struct kobj_attribute damon_sysfs_scheme_apply_interval_us_attr =
+		__ATTR_RW_MODE(apply_interval_us, 0600);
+
 static struct attribute *damon_sysfs_scheme_attrs[] = {
 	&damon_sysfs_scheme_action_attr.attr,
+	&damon_sysfs_scheme_apply_interval_us_attr.attr,
 	NULL,
 };
 ATTRIBUTE_GROUPS(damon_sysfs_scheme);
@@ -1413,7 +1438,11 @@ static int damon_sysfs_schemes_add_dirs(struct damon_sysfs_schemes *schemes,
 	schemes->schemes_arr = schemes_arr;
 
 	for (i = 0; i < nr_schemes; i++) {
-		scheme = damon_sysfs_scheme_alloc(DAMOS_STAT);
+		/*
+		 * apply_interval_us as 0 means same to aggregation interval
+		 * (same to before-apply_interval behavior)
+		 */
+		scheme = damon_sysfs_scheme_alloc(DAMOS_STAT, 0);
 		if (!scheme) {
 			damon_sysfs_schemes_rm_dirs(schemes);
 			return -ENOMEM;
@@ -1610,8 +1639,8 @@ static struct damos *damon_sysfs_mk_scheme(
 		.low = sysfs_wmarks->low,
 	};
 
-	scheme = damon_new_scheme(&pattern, sysfs_scheme->action, 0, &quota,
-			&wmarks);
+	scheme = damon_new_scheme(&pattern, sysfs_scheme->action,
+			sysfs_scheme->apply_interval_us, &quota, &wmarks);
 	if (!scheme)
 		return NULL;
 
@@ -1641,6 +1670,7 @@ static void damon_sysfs_update_scheme(struct damos *scheme,
 	scheme->pattern.max_age_region = access_pattern->age->max;
 
 	scheme->action = sysfs_scheme->action;
+	scheme->apply_interval_us = sysfs_scheme->apply_interval_us;
 
 	scheme->quota.ms = sysfs_quotas->ms;
 	scheme->quota.sz = sysfs_quotas->sz;
-- 
2.25.1