mm/damon/sysfs-schemes: support DAMOS apply interval

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

Link: https://lkml.kernel.org/r/20230916020945.47296-7-sj@kernel.orgSigned-off-by: SeongJae Park <sj@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

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;