mm/damon/sysfs-schemes: add target_nid on sysfs-schemes

This patch adds target_nid under
/sys/kernel/mm/damon/admin/kdamonds/<N>/contexts/<N>/schemes/<N>/

The 'target_nid' can be used as the destination node for DAMOS actions
such as DAMOS_MIGRATE_{HOT,COLD} in the follow up patches.

[[e-mail]: document target_nid file]
Link: https://lkml.kernel.org/r/[e-mail]
Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: Hyeongtak Ji <[e-mail]>
Signed-off-by: Honggyu Kim <[e-mail]>
Signed-off-by: SeongJae Park <[e-mail]>
Cc: Gregory Price <[e-mail]>
Cc: Hyeonggon Yoo <[e-mail]>
Cc: Masami Hiramatsu (Google) <[e-mail]>
Cc: Mathieu Desnoyers <[e-mail]>
Cc: Rakie Kim <[e-mail]>
Cc: Steven Rostedt (Google) <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>

Documentation/ABI/testing/sysfs-kernel-mm-damon

···
 Description:	Writing to and reading from this file sets and gets the action
 		of the scheme.
 
+What:		/sys/kernel/mm/damon/admin/kdamonds/<K>/contexts/<C>/schemes/<S>/target_nid
+Date:		Jun 2024
+Contact:	SeongJae Park <[e-mail]>
+Description:	Action's target NUMA node id.  Supported by only relevant
+		actions.
+
 What:		/sys/kernel/mm/damon/admin/kdamonds/<K>/contexts/<C>/schemes/<S>/apply_interval_us
 Date:		Sep 2023
 Contact:	SeongJae Park <[e-mail]>

include/linux/damon.h

···
  * @apply_interval_us:	The time between applying the @action.
  * @quota:		Control the aggressiveness of this scheme.
  * @wmarks:		Watermarks for automated (in)activation of this scheme.
+ * @target_nid:		Destination node if @action is "migrate_{hot,cold}".
  * @filters:		Additional set of &struct damos_filter for &action.
  * @stat:		Statistics of this scheme.
  * @list:		List head for siblings.
···
  * system situations using &wmarks.  If all schemes that registered to the
  * monitoring context are inactive, DAMON stops monitoring either, and just
  * repeatedly checks the watermarks.
+ *
+ * @target_nid is used to set the migration target node for migrate_hot or
+ * migrate_cold actions, which means it's only meaningful when @action is either
+ * "migrate_hot" or "migrate_cold".
  *
  * Before applying the &action to a memory region, &struct damon_operations
  * implementation could check pages of the region and skip &action to respect
···
 /* public: */
 	struct damos_quota quota;
 	struct damos_watermarks wmarks;
+	union {
+		int target_nid;
+	};
 	struct list_head filters;
 	struct damos_stat stat;
 	struct list_head list;
···
 			enum damos_action action,
 			unsigned long apply_interval_us,
 			struct damos_quota *quota,
-			struct damos_watermarks *wmarks);
+			struct damos_watermarks *wmarks,
+			int target_nid);
 void damon_add_scheme(struct damon_ctx *ctx, struct damos *s);
 void damon_destroy_scheme(struct damos *s);
 

mm/damon/core.c

···
 			enum damos_action action,
 			unsigned long apply_interval_us,
 			struct damos_quota *quota,
-			struct damos_watermarks *wmarks)
+			struct damos_watermarks *wmarks,
+			int target_nid)
 {
 	struct damos *scheme;
 
···
 
 	scheme->wmarks = *wmarks;
 	scheme->wmarks.activated = true;
+
+	scheme->target_nid = target_nid;
 
 	return scheme;
 }

mm/damon/dbgfs.c

···
 
 		pos += parsed;
 		scheme = damon_new_scheme(&pattern, action, 0, &quota,
-				&wmarks);
+				&wmarks, NUMA_NO_NODE);
 		if (!scheme)
 			goto fail;
 

mm/damon/lru_sort.c

···
 			/* under the quota. */
 			&quota,
 			/* (De)activate this according to the watermarks. */
-			&damon_lru_sort_wmarks);
+			&damon_lru_sort_wmarks,
+			NUMA_NO_NODE);
 }
 
 /* Create a DAMON-based operation scheme for hot memory regions */

mm/damon/reclaim.c

···
 			/* under the quota. */
 			&damon_reclaim_quota,
 			/* (De)activate this according to the watermarks. */
-			&damon_reclaim_wmarks);
+			&damon_reclaim_wmarks,
+			NUMA_NO_NODE);
 }
 
 static void damon_reclaim_copy_quota_status(struct damos_quota *dst,

mm/damon/sysfs-schemes.c

···
  */
 
 #include <linux/slab.h>
+#include <linux/numa.h>
 
 #include "sysfs-common.h"
 
···
 	struct damon_sysfs_scheme_filters *filters;
 	struct damon_sysfs_stats *stats;
 	struct damon_sysfs_scheme_regions *tried_regions;
+	int target_nid;
 };
 
 /* This should match with enum damos_action */
···
 	scheme->kobj = (struct kobject){};
 	scheme->action = action;
 	scheme->apply_interval_us = apply_interval_us;
+	scheme->target_nid = NUMA_NO_NODE;
 	return scheme;
 }
 
···
 	return err ? err : count;
 }
 
+static ssize_t target_nid_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, "%d\n", scheme->target_nid);
+}
+
+static ssize_t target_nid_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 = 0;
+
+	/* TODO: error handling for target_nid range. */
+	err = kstrtoint(buf, 0, &scheme->target_nid);
+
+	return err ? err : count;
+}
+
 static void damon_sysfs_scheme_release(struct kobject *kobj)
 {
 	kfree(container_of(kobj, struct damon_sysfs_scheme, kobj));
···
 static struct kobj_attribute damon_sysfs_scheme_apply_interval_us_attr =
 		__ATTR_RW_MODE(apply_interval_us, 0600);
 
+static struct kobj_attribute damon_sysfs_scheme_target_nid_attr =
+		__ATTR_RW_MODE(target_nid, 0600);
+
 static struct attribute *damon_sysfs_scheme_attrs[] = {
 	&damon_sysfs_scheme_action_attr.attr,
 	&damon_sysfs_scheme_apply_interval_us_attr.attr,
+	&damon_sysfs_scheme_target_nid_attr.attr,
 	NULL,
 };
 ATTRIBUTE_GROUPS(damon_sysfs_scheme);
···
 	};
 
 	scheme = damon_new_scheme(&pattern, sysfs_scheme->action,
-			sysfs_scheme->apply_interval_us, &quota, &wmarks);
+			sysfs_scheme->apply_interval_us, &quota, &wmarks,
+			sysfs_scheme->target_nid);
 	if (!scheme)
 		return NULL;
 
···
 
 	scheme->action = sysfs_scheme->action;
 	scheme->apply_interval_us = sysfs_scheme->apply_interval_us;
+	scheme->target_nid = sysfs_scheme->target_nid;
 
 	scheme->quota.ms = sysfs_quotas->ms;
 	scheme->quota.sz = sysfs_quotas->sz;