Adding upstream version 6.1.76.upstream/6.1.76upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1310 insertions, 0 deletions

diff --git a/mm/damon/core.c b/mm/damon/core.c
new file mode 100644
index 000000000..5db9bec8a
--- /dev/null
+++ b/mm/damon/core.c
@@ -0,0 +1,1310 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Data Access Monitor
+ *
+ * Author: SeongJae Park <sjpark@amazon.de>
+ */
+
+#define pr_fmt(fmt) "damon: " fmt
+
+#include <linux/damon.h>
+#include <linux/delay.h>
+#include <linux/kthread.h>
+#include <linux/mm.h>
+#include <linux/slab.h>
+#include <linux/string.h>
+
+#define CREATE_TRACE_POINTS
+#include <trace/events/damon.h>
+
+#ifdef CONFIG_DAMON_KUNIT_TEST
+#undef DAMON_MIN_REGION
+#define DAMON_MIN_REGION 1
+#endif
+
+static DEFINE_MUTEX(damon_lock);
+static int nr_running_ctxs;
+static bool running_exclusive_ctxs;
+
+static DEFINE_MUTEX(damon_ops_lock);
+static struct damon_operations damon_registered_ops[NR_DAMON_OPS];
+
+static struct kmem_cache *damon_region_cache __ro_after_init;
+
+/* Should be called under damon_ops_lock with id smaller than NR_DAMON_OPS */
+static bool __damon_is_registered_ops(enum damon_ops_id id)
+{
+	struct damon_operations empty_ops = {};
+
+	if (!memcmp(&empty_ops, &damon_registered_ops[id], sizeof(empty_ops)))
+		return false;
+	return true;
+}
+
+/**
+ * damon_is_registered_ops() - Check if a given damon_operations is registered.
+ * @id:	Id of the damon_operations to check if registered.
+ *
+ * Return: true if the ops is set, false otherwise.
+ */
+bool damon_is_registered_ops(enum damon_ops_id id)
+{
+	bool registered;
+
+	if (id >= NR_DAMON_OPS)
+		return false;
+	mutex_lock(&damon_ops_lock);
+	registered = __damon_is_registered_ops(id);
+	mutex_unlock(&damon_ops_lock);
+	return registered;
+}
+
+/**
+ * damon_register_ops() - Register a monitoring operations set to DAMON.
+ * @ops:	monitoring operations set to register.
+ *
+ * This function registers a monitoring operations set of valid &struct
+ * damon_operations->id so that others can find and use them later.
+ *
+ * Return: 0 on success, negative error code otherwise.
+ */
+int damon_register_ops(struct damon_operations *ops)
+{
+	int err = 0;
+
+	if (ops->id >= NR_DAMON_OPS)
+		return -EINVAL;
+	mutex_lock(&damon_ops_lock);
+	/* Fail for already registered ops */
+	if (__damon_is_registered_ops(ops->id)) {
+		err = -EINVAL;
+		goto out;
+	}
+	damon_registered_ops[ops->id] = *ops;
+out:
+	mutex_unlock(&damon_ops_lock);
+	return err;
+}
+
+/**
+ * damon_select_ops() - Select a monitoring operations to use with the context.
+ * @ctx:	monitoring context to use the operations.
+ * @id:		id of the registered monitoring operations to select.
+ *
+ * This function finds registered monitoring operations set of @id and make
+ * @ctx to use it.
+ *
+ * Return: 0 on success, negative error code otherwise.
+ */
+int damon_select_ops(struct damon_ctx *ctx, enum damon_ops_id id)
+{
+	int err = 0;
+
+	if (id >= NR_DAMON_OPS)
+		return -EINVAL;
+
+	mutex_lock(&damon_ops_lock);
+	if (!__damon_is_registered_ops(id))
+		err = -EINVAL;
+	else
+		ctx->ops = damon_registered_ops[id];
+	mutex_unlock(&damon_ops_lock);
+	return err;
+}
+
+/*
+ * Construct a damon_region struct
+ *
+ * Returns the pointer to the new struct if success, or NULL otherwise
+ */
+struct damon_region *damon_new_region(unsigned long start, unsigned long end)
+{
+	struct damon_region *region;
+
+	region = kmem_cache_alloc(damon_region_cache, GFP_KERNEL);
+	if (!region)
+		return NULL;
+
+	region->ar.start = start;
+	region->ar.end = end;
+	region->nr_accesses = 0;
+	INIT_LIST_HEAD(&region->list);
+
+	region->age = 0;
+	region->last_nr_accesses = 0;
+
+	return region;
+}
+
+void damon_add_region(struct damon_region *r, struct damon_target *t)
+{
+	list_add_tail(&r->list, &t->regions_list);
+	t->nr_regions++;
+}
+
+static void damon_del_region(struct damon_region *r, struct damon_target *t)
+{
+	list_del(&r->list);
+	t->nr_regions--;
+}
+
+static void damon_free_region(struct damon_region *r)
+{
+	kmem_cache_free(damon_region_cache, r);
+}
+
+void damon_destroy_region(struct damon_region *r, struct damon_target *t)
+{
+	damon_del_region(r, t);
+	damon_free_region(r);
+}
+
+/*
+ * Check whether a region is intersecting an address range
+ *
+ * Returns true if it is.
+ */
+static bool damon_intersect(struct damon_region *r,
+		struct damon_addr_range *re)
+{
+	return !(r->ar.end <= re->start || re->end <= r->ar.start);
+}
+
+/*
+ * Fill holes in regions with new regions.
+ */
+static int damon_fill_regions_holes(struct damon_region *first,
+		struct damon_region *last, struct damon_target *t)
+{
+	struct damon_region *r = first;
+
+	damon_for_each_region_from(r, t) {
+		struct damon_region *next, *newr;
+
+		if (r == last)
+			break;
+		next = damon_next_region(r);
+		if (r->ar.end != next->ar.start) {
+			newr = damon_new_region(r->ar.end, next->ar.start);
+			if (!newr)
+				return -ENOMEM;
+			damon_insert_region(newr, r, next, t);
+		}
+	}
+	return 0;
+}
+
+/*
+ * damon_set_regions() - Set regions of a target for given address ranges.
+ * @t:		the given target.
+ * @ranges:	array of new monitoring target ranges.
+ * @nr_ranges:	length of @ranges.
+ *
+ * This function adds new regions to, or modify existing regions of a
+ * monitoring target to fit in specific ranges.
+ *
+ * Return: 0 if success, or negative error code otherwise.
+ */
+int damon_set_regions(struct damon_target *t, struct damon_addr_range *ranges,
+		unsigned int nr_ranges)
+{
+	struct damon_region *r, *next;
+	unsigned int i;
+	int err;
+
+	/* Remove regions which are not in the new ranges */
+	damon_for_each_region_safe(r, next, t) {
+		for (i = 0; i < nr_ranges; i++) {
+			if (damon_intersect(r, &ranges[i]))
+				break;
+		}
+		if (i == nr_ranges)
+			damon_destroy_region(r, t);
+	}
+
+	r = damon_first_region(t);
+	/* Add new regions or resize existing regions to fit in the ranges */
+	for (i = 0; i < nr_ranges; i++) {
+		struct damon_region *first = NULL, *last, *newr;
+		struct damon_addr_range *range;
+
+		range = &ranges[i];
+		/* Get the first/last regions intersecting with the range */
+		damon_for_each_region_from(r, t) {
+			if (damon_intersect(r, range)) {
+				if (!first)
+					first = r;
+				last = r;
+			}
+			if (r->ar.start >= range->end)
+				break;
+		}
+		if (!first) {
+			/* no region intersects with this range */
+			newr = damon_new_region(
+					ALIGN_DOWN(range->start,
+						DAMON_MIN_REGION),
+					ALIGN(range->end, DAMON_MIN_REGION));
+			if (!newr)
+				return -ENOMEM;
+			damon_insert_region(newr, damon_prev_region(r), r, t);
+		} else {
+			/* resize intersecting regions to fit in this range */
+			first->ar.start = ALIGN_DOWN(range->start,
+					DAMON_MIN_REGION);
+			last->ar.end = ALIGN(range->end, DAMON_MIN_REGION);
+
+			/* fill possible holes in the range */
+			err = damon_fill_regions_holes(first, last, t);
+			if (err)
+				return err;
+		}
+	}
+	return 0;
+}
+
+/* initialize private fields of damos_quota and return the pointer */
+static struct damos_quota *damos_quota_init_priv(struct damos_quota *quota)
+{
+	quota->total_charged_sz = 0;
+	quota->total_charged_ns = 0;
+	quota->esz = 0;
+	quota->charged_sz = 0;
+	quota->charged_from = 0;
+	quota->charge_target_from = NULL;
+	quota->charge_addr_from = 0;
+	return quota;
+}
+
+struct damos *damon_new_scheme(struct damos_access_pattern *pattern,
+			enum damos_action action, struct damos_quota *quota,
+			struct damos_watermarks *wmarks)
+{
+	struct damos *scheme;
+
+	scheme = kmalloc(sizeof(*scheme), GFP_KERNEL);
+	if (!scheme)
+		return NULL;
+	scheme->pattern = *pattern;
+	scheme->action = action;
+	scheme->stat = (struct damos_stat){};
+	INIT_LIST_HEAD(&scheme->list);
+
+	scheme->quota = *(damos_quota_init_priv(quota));
+
+	scheme->wmarks = *wmarks;
+	scheme->wmarks.activated = true;
+
+	return scheme;
+}
+
+void damon_add_scheme(struct damon_ctx *ctx, struct damos *s)
+{
+	list_add_tail(&s->list, &ctx->schemes);
+}
+
+static void damon_del_scheme(struct damos *s)
+{
+	list_del(&s->list);
+}
+
+static void damon_free_scheme(struct damos *s)
+{
+	kfree(s);
+}
+
+void damon_destroy_scheme(struct damos *s)
+{
+	damon_del_scheme(s);
+	damon_free_scheme(s);
+}
+
+/*
+ * Construct a damon_target struct
+ *
+ * Returns the pointer to the new struct if success, or NULL otherwise
+ */
+struct damon_target *damon_new_target(void)
+{
+	struct damon_target *t;
+
+	t = kmalloc(sizeof(*t), GFP_KERNEL);
+	if (!t)
+		return NULL;
+
+	t->pid = NULL;
+	t->nr_regions = 0;
+	INIT_LIST_HEAD(&t->regions_list);
+	INIT_LIST_HEAD(&t->list);
+
+	return t;
+}
+
+void damon_add_target(struct damon_ctx *ctx, struct damon_target *t)
+{
+	list_add_tail(&t->list, &ctx->adaptive_targets);
+}
+
+bool damon_targets_empty(struct damon_ctx *ctx)
+{
+	return list_empty(&ctx->adaptive_targets);
+}
+
+static void damon_del_target(struct damon_target *t)
+{
+	list_del(&t->list);
+}
+
+void damon_free_target(struct damon_target *t)
+{
+	struct damon_region *r, *next;
+
+	damon_for_each_region_safe(r, next, t)
+		damon_free_region(r);
+	kfree(t);
+}
+
+void damon_destroy_target(struct damon_target *t)
+{
+	damon_del_target(t);
+	damon_free_target(t);
+}
+
+unsigned int damon_nr_regions(struct damon_target *t)
+{
+	return t->nr_regions;
+}
+
+struct damon_ctx *damon_new_ctx(void)
+{
+	struct damon_ctx *ctx;
+
+	ctx = kzalloc(sizeof(*ctx), GFP_KERNEL);
+	if (!ctx)
+		return NULL;
+
+	init_completion(&ctx->kdamond_started);
+
+	ctx->attrs.sample_interval = 5 * 1000;
+	ctx->attrs.aggr_interval = 100 * 1000;
+	ctx->attrs.ops_update_interval = 60 * 1000 * 1000;
+
+	ktime_get_coarse_ts64(&ctx->last_aggregation);
+	ctx->last_ops_update = ctx->last_aggregation;
+
+	mutex_init(&ctx->kdamond_lock);
+
+	ctx->attrs.min_nr_regions = 10;
+	ctx->attrs.max_nr_regions = 1000;
+
+	INIT_LIST_HEAD(&ctx->adaptive_targets);
+	INIT_LIST_HEAD(&ctx->schemes);
+
+	return ctx;
+}
+
+static void damon_destroy_targets(struct damon_ctx *ctx)
+{
+	struct damon_target *t, *next_t;
+
+	if (ctx->ops.cleanup) {
+		ctx->ops.cleanup(ctx);
+		return;
+	}
+
+	damon_for_each_target_safe(t, next_t, ctx)
+		damon_destroy_target(t);
+}
+
+void damon_destroy_ctx(struct damon_ctx *ctx)
+{
+	struct damos *s, *next_s;
+
+	damon_destroy_targets(ctx);
+
+	damon_for_each_scheme_safe(s, next_s, ctx)
+		damon_destroy_scheme(s);
+
+	kfree(ctx);
+}
+
+/**
+ * damon_set_attrs() - Set attributes for the monitoring.
+ * @ctx:		monitoring context
+ * @attrs:		monitoring attributes
+ *
+ * This function should not be called while the kdamond is running.
+ * Every time interval is in micro-seconds.
+ *
+ * Return: 0 on success, negative error code otherwise.
+ */
+int damon_set_attrs(struct damon_ctx *ctx, struct damon_attrs *attrs)
+{
+	if (attrs->min_nr_regions < 3)
+		return -EINVAL;
+	if (attrs->min_nr_regions > attrs->max_nr_regions)
+		return -EINVAL;
+
+	ctx->attrs = *attrs;
+	return 0;
+}
+
+/**
+ * damon_set_schemes() - Set data access monitoring based operation schemes.
+ * @ctx:	monitoring context
+ * @schemes:	array of the schemes
+ * @nr_schemes:	number of entries in @schemes
+ *
+ * This function should not be called while the kdamond of the context is
+ * running.
+ */
+void damon_set_schemes(struct damon_ctx *ctx, struct damos **schemes,
+			ssize_t nr_schemes)
+{
+	struct damos *s, *next;
+	ssize_t i;
+
+	damon_for_each_scheme_safe(s, next, ctx)
+		damon_destroy_scheme(s);
+	for (i = 0; i < nr_schemes; i++)
+		damon_add_scheme(ctx, schemes[i]);
+}
+
+/**
+ * damon_nr_running_ctxs() - Return number of currently running contexts.
+ */
+int damon_nr_running_ctxs(void)
+{
+	int nr_ctxs;
+
+	mutex_lock(&damon_lock);
+	nr_ctxs = nr_running_ctxs;
+	mutex_unlock(&damon_lock);
+
+	return nr_ctxs;
+}
+
+/* Returns the size upper limit for each monitoring region */
+static unsigned long damon_region_sz_limit(struct damon_ctx *ctx)
+{
+	struct damon_target *t;
+	struct damon_region *r;
+	unsigned long sz = 0;
+
+	damon_for_each_target(t, ctx) {
+		damon_for_each_region(r, t)
+			sz += damon_sz_region(r);
+	}
+
+	if (ctx->attrs.min_nr_regions)
+		sz /= ctx->attrs.min_nr_regions;
+	if (sz < DAMON_MIN_REGION)
+		sz = DAMON_MIN_REGION;
+
+	return sz;
+}
+
+static int kdamond_fn(void *data);
+
+/*
+ * __damon_start() - Starts monitoring with given context.
+ * @ctx:	monitoring context
+ *
+ * This function should be called while damon_lock is hold.
+ *
+ * Return: 0 on success, negative error code otherwise.
+ */
+static int __damon_start(struct damon_ctx *ctx)
+{
+	int err = -EBUSY;
+
+	mutex_lock(&ctx->kdamond_lock);
+	if (!ctx->kdamond) {
+		err = 0;
+		reinit_completion(&ctx->kdamond_started);
+		ctx->kdamond = kthread_run(kdamond_fn, ctx, "kdamond.%d",
+				nr_running_ctxs);
+		if (IS_ERR(ctx->kdamond)) {
+			err = PTR_ERR(ctx->kdamond);
+			ctx->kdamond = NULL;
+		} else {
+			wait_for_completion(&ctx->kdamond_started);
+		}
+	}
+	mutex_unlock(&ctx->kdamond_lock);
+
+	return err;
+}
+
+/**
+ * damon_start() - Starts the monitorings for a given group of contexts.
+ * @ctxs:	an array of the pointers for contexts to start monitoring
+ * @nr_ctxs:	size of @ctxs
+ * @exclusive:	exclusiveness of this contexts group
+ *
+ * This function starts a group of monitoring threads for a group of monitoring
+ * contexts.  One thread per each context is created and run in parallel.  The
+ * caller should handle synchronization between the threads by itself.  If
+ * @exclusive is true and a group of threads that created by other
+ * 'damon_start()' call is currently running, this function does nothing but
+ * returns -EBUSY.
+ *
+ * Return: 0 on success, negative error code otherwise.
+ */
+int damon_start(struct damon_ctx **ctxs, int nr_ctxs, bool exclusive)
+{
+	int i;
+	int err = 0;
+
+	mutex_lock(&damon_lock);
+	if ((exclusive && nr_running_ctxs) ||
+			(!exclusive && running_exclusive_ctxs)) {
+		mutex_unlock(&damon_lock);
+		return -EBUSY;
+	}
+
+	for (i = 0; i < nr_ctxs; i++) {
+		err = __damon_start(ctxs[i]);
+		if (err)
+			break;
+		nr_running_ctxs++;
+	}
+	if (exclusive && nr_running_ctxs)
+		running_exclusive_ctxs = true;
+	mutex_unlock(&damon_lock);
+
+	return err;
+}
+
+/*
+ * __damon_stop() - Stops monitoring of a given context.
+ * @ctx:	monitoring context
+ *
+ * Return: 0 on success, negative error code otherwise.
+ */
+static int __damon_stop(struct damon_ctx *ctx)
+{
+	struct task_struct *tsk;
+
+	mutex_lock(&ctx->kdamond_lock);
+	tsk = ctx->kdamond;
+	if (tsk) {
+		get_task_struct(tsk);
+		mutex_unlock(&ctx->kdamond_lock);
+		kthread_stop(tsk);
+		put_task_struct(tsk);
+		return 0;
+	}
+	mutex_unlock(&ctx->kdamond_lock);
+
+	return -EPERM;
+}
+
+/**
+ * damon_stop() - Stops the monitorings for a given group of contexts.
+ * @ctxs:	an array of the pointers for contexts to stop monitoring
+ * @nr_ctxs:	size of @ctxs
+ *
+ * Return: 0 on success, negative error code otherwise.
+ */
+int damon_stop(struct damon_ctx **ctxs, int nr_ctxs)
+{
+	int i, err = 0;
+
+	for (i = 0; i < nr_ctxs; i++) {
+		/* nr_running_ctxs is decremented in kdamond_fn */
+		err = __damon_stop(ctxs[i]);
+		if (err)
+			break;
+	}
+	return err;
+}
+
+/*
+ * damon_check_reset_time_interval() - Check if a time interval is elapsed.
+ * @baseline:	the time to check whether the interval has elapsed since
+ * @interval:	the time interval (microseconds)
+ *
+ * See whether the given time interval has passed since the given baseline
+ * time.  If so, it also updates the baseline to current time for next check.
+ *
+ * Return:	true if the time interval has passed, or false otherwise.
+ */
+static bool damon_check_reset_time_interval(struct timespec64 *baseline,
+		unsigned long interval)
+{
+	struct timespec64 now;
+
+	ktime_get_coarse_ts64(&now);
+	if ((timespec64_to_ns(&now) - timespec64_to_ns(baseline)) <
+			interval * 1000)
+		return false;
+	*baseline = now;
+	return true;
+}
+
+/*
+ * Check whether it is time to flush the aggregated information
+ */
+static bool kdamond_aggregate_interval_passed(struct damon_ctx *ctx)
+{
+	return damon_check_reset_time_interval(&ctx->last_aggregation,
+			ctx->attrs.aggr_interval);
+}
+
+/*
+ * Reset the aggregated monitoring results ('nr_accesses' of each region).
+ */
+static void kdamond_reset_aggregated(struct damon_ctx *c)
+{
+	struct damon_target *t;
+	unsigned int ti = 0;	/* target's index */
+
+	damon_for_each_target(t, c) {
+		struct damon_region *r;
+
+		damon_for_each_region(r, t) {
+			trace_damon_aggregated(t, ti, r, damon_nr_regions(t));
+			r->last_nr_accesses = r->nr_accesses;
+			r->nr_accesses = 0;
+		}
+		ti++;
+	}
+}
+
+static void damon_split_region_at(struct damon_target *t,
+				  struct damon_region *r, unsigned long sz_r);
+
+static bool __damos_valid_target(struct damon_region *r, struct damos *s)
+{
+	unsigned long sz;
+
+	sz = damon_sz_region(r);
+	return s->pattern.min_sz_region <= sz &&
+		sz <= s->pattern.max_sz_region &&
+		s->pattern.min_nr_accesses <= r->nr_accesses &&
+		r->nr_accesses <= s->pattern.max_nr_accesses &&
+		s->pattern.min_age_region <= r->age &&
+		r->age <= s->pattern.max_age_region;
+}
+
+static bool damos_valid_target(struct damon_ctx *c, struct damon_target *t,
+		struct damon_region *r, struct damos *s)
+{
+	bool ret = __damos_valid_target(r, s);
+
+	if (!ret || !s->quota.esz || !c->ops.get_scheme_score)
+		return ret;
+
+	return c->ops.get_scheme_score(c, t, r, s) >= s->quota.min_score;
+}
+
+static void damon_do_apply_schemes(struct damon_ctx *c,
+				   struct damon_target *t,
+				   struct damon_region *r)
+{
+	struct damos *s;
+
+	damon_for_each_scheme(s, c) {
+		struct damos_quota *quota = &s->quota;
+		unsigned long sz = damon_sz_region(r);
+		struct timespec64 begin, end;
+		unsigned long sz_applied = 0;
+
+		if (!s->wmarks.activated)
+			continue;
+
+		/* Check the quota */
+		if (quota->esz && quota->charged_sz >= quota->esz)
+			continue;
+
+		/* Skip previously charged regions */
+		if (quota->charge_target_from) {
+			if (t != quota->charge_target_from)
+				continue;
+			if (r == damon_last_region(t)) {
+				quota->charge_target_from = NULL;
+				quota->charge_addr_from = 0;
+				continue;
+			}
+			if (quota->charge_addr_from &&
+					r->ar.end <= quota->charge_addr_from)
+				continue;
+
+			if (quota->charge_addr_from && r->ar.start <
+					quota->charge_addr_from) {
+				sz = ALIGN_DOWN(quota->charge_addr_from -
+						r->ar.start, DAMON_MIN_REGION);
+				if (!sz) {
+					if (damon_sz_region(r) <=
+					    DAMON_MIN_REGION)
+						continue;
+					sz = DAMON_MIN_REGION;
+				}
+				damon_split_region_at(t, r, sz);
+				r = damon_next_region(r);
+				sz = damon_sz_region(r);
+			}
+			quota->charge_target_from = NULL;
+			quota->charge_addr_from = 0;
+		}
+
+		if (!damos_valid_target(c, t, r, s))
+			continue;
+
+		/* Apply the scheme */
+		if (c->ops.apply_scheme) {
+			if (quota->esz &&
+					quota->charged_sz + sz > quota->esz) {
+				sz = ALIGN_DOWN(quota->esz - quota->charged_sz,
+						DAMON_MIN_REGION);
+				if (!sz)
+					goto update_stat;
+				damon_split_region_at(t, r, sz);
+			}
+			ktime_get_coarse_ts64(&begin);
+			sz_applied = c->ops.apply_scheme(c, t, r, s);
+			ktime_get_coarse_ts64(&end);
+			quota->total_charged_ns += timespec64_to_ns(&end) -
+				timespec64_to_ns(&begin);
+			quota->charged_sz += sz;
+			if (quota->esz && quota->charged_sz >= quota->esz) {
+				quota->charge_target_from = t;
+				quota->charge_addr_from = r->ar.end + 1;
+			}
+		}
+		if (s->action != DAMOS_STAT)
+			r->age = 0;
+
+update_stat:
+		s->stat.nr_tried++;
+		s->stat.sz_tried += sz;
+		if (sz_applied)
+			s->stat.nr_applied++;
+		s->stat.sz_applied += sz_applied;
+	}
+}
+
+/* Shouldn't be called if quota->ms and quota->sz are zero */
+static void damos_set_effective_quota(struct damos_quota *quota)
+{
+	unsigned long throughput;
+	unsigned long esz;
+
+	if (!quota->ms) {
+		quota->esz = quota->sz;
+		return;
+	}
+
+	if (quota->total_charged_ns)
+		throughput = quota->total_charged_sz * 1000000 /
+			quota->total_charged_ns;
+	else
+		throughput = PAGE_SIZE * 1024;
+	esz = throughput * quota->ms;
+
+	if (quota->sz && quota->sz < esz)
+		esz = quota->sz;
+	quota->esz = esz;
+}
+
+static void kdamond_apply_schemes(struct damon_ctx *c)
+{
+	struct damon_target *t;
+	struct damon_region *r, *next_r;
+	struct damos *s;
+
+	damon_for_each_scheme(s, c) {
+		struct damos_quota *quota = &s->quota;
+		unsigned long cumulated_sz;
+		unsigned int score, max_score = 0;
+
+		if (!s->wmarks.activated)
+			continue;
+
+		if (!quota->ms && !quota->sz)
+			continue;
+
+		/* New charge window starts */
+		if (time_after_eq(jiffies, quota->charged_from +
+					msecs_to_jiffies(
+						quota->reset_interval))) {
+			if (quota->esz && quota->charged_sz >= quota->esz)
+				s->stat.qt_exceeds++;
+			quota->total_charged_sz += quota->charged_sz;
+			quota->charged_from = jiffies;
+			quota->charged_sz = 0;
+			damos_set_effective_quota(quota);
+		}
+
+		if (!c->ops.get_scheme_score)
+			continue;
+
+		/* Fill up the score histogram */
+		memset(quota->histogram, 0, sizeof(quota->histogram));
+		damon_for_each_target(t, c) {
+			damon_for_each_region(r, t) {
+				if (!__damos_valid_target(r, s))
+					continue;
+				score = c->ops.get_scheme_score(
+						c, t, r, s);
+				quota->histogram[score] += damon_sz_region(r);
+				if (score > max_score)
+					max_score = score;
+			}
+		}
+
+		/* Set the min score limit */
+		for (cumulated_sz = 0, score = max_score; ; score--) {
+			cumulated_sz += quota->histogram[score];
+			if (cumulated_sz >= quota->esz || !score)
+				break;
+		}
+		quota->min_score = score;
+	}
+
+	damon_for_each_target(t, c) {
+		damon_for_each_region_safe(r, next_r, t)
+			damon_do_apply_schemes(c, t, r);
+	}
+}
+
+/*
+ * Merge two adjacent regions into one region
+ */
+static void damon_merge_two_regions(struct damon_target *t,
+		struct damon_region *l, struct damon_region *r)
+{
+	unsigned long sz_l = damon_sz_region(l), sz_r = damon_sz_region(r);
+
+	l->nr_accesses = (l->nr_accesses * sz_l + r->nr_accesses * sz_r) /
+			(sz_l + sz_r);
+	l->age = (l->age * sz_l + r->age * sz_r) / (sz_l + sz_r);
+	l->ar.end = r->ar.end;
+	damon_destroy_region(r, t);
+}
+
+/*
+ * Merge adjacent regions having similar access frequencies
+ *
+ * t		target affected by this merge operation
+ * thres	'->nr_accesses' diff threshold for the merge
+ * sz_limit	size upper limit of each region
+ */
+static void damon_merge_regions_of(struct damon_target *t, unsigned int thres,
+				   unsigned long sz_limit)
+{
+	struct damon_region *r, *prev = NULL, *next;
+
+	damon_for_each_region_safe(r, next, t) {
+		if (abs(r->nr_accesses - r->last_nr_accesses) > thres)
+			r->age = 0;
+		else
+			r->age++;
+
+		if (prev && prev->ar.end == r->ar.start &&
+		    abs(prev->nr_accesses - r->nr_accesses) <= thres &&
+		    damon_sz_region(prev) + damon_sz_region(r) <= sz_limit)
+			damon_merge_two_regions(t, prev, r);
+		else
+			prev = r;
+	}
+}
+
+/*
+ * Merge adjacent regions having similar access frequencies
+ *
+ * threshold	'->nr_accesses' diff threshold for the merge
+ * sz_limit	size upper limit of each region
+ *
+ * This function merges monitoring target regions which are adjacent and their
+ * access frequencies are similar.  This is for minimizing the monitoring
+ * overhead under the dynamically changeable access pattern.  If a merge was
+ * unnecessarily made, later 'kdamond_split_regions()' will revert it.
+ */
+static void kdamond_merge_regions(struct damon_ctx *c, unsigned int threshold,
+				  unsigned long sz_limit)
+{
+	struct damon_target *t;
+
+	damon_for_each_target(t, c)
+		damon_merge_regions_of(t, threshold, sz_limit);
+}
+
+/*
+ * Split a region in two
+ *
+ * r		the region to be split
+ * sz_r		size of the first sub-region that will be made
+ */
+static void damon_split_region_at(struct damon_target *t,
+				  struct damon_region *r, unsigned long sz_r)
+{
+	struct damon_region *new;
+
+	new = damon_new_region(r->ar.start + sz_r, r->ar.end);
+	if (!new)
+		return;
+
+	r->ar.end = new->ar.start;
+
+	new->age = r->age;
+	new->last_nr_accesses = r->last_nr_accesses;
+
+	damon_insert_region(new, r, damon_next_region(r), t);
+}
+
+/* Split every region in the given target into 'nr_subs' regions */
+static void damon_split_regions_of(struct damon_target *t, int nr_subs)
+{
+	struct damon_region *r, *next;
+	unsigned long sz_region, sz_sub = 0;
+	int i;
+
+	damon_for_each_region_safe(r, next, t) {
+		sz_region = damon_sz_region(r);
+
+		for (i = 0; i < nr_subs - 1 &&
+				sz_region > 2 * DAMON_MIN_REGION; i++) {
+			/*
+			 * Randomly select size of left sub-region to be at
+			 * least 10 percent and at most 90% of original region
+			 */
+			sz_sub = ALIGN_DOWN(damon_rand(1, 10) *
+					sz_region / 10, DAMON_MIN_REGION);
+			/* Do not allow blank region */
+			if (sz_sub == 0 || sz_sub >= sz_region)
+				continue;
+
+			damon_split_region_at(t, r, sz_sub);
+			sz_region = sz_sub;
+		}
+	}
+}
+
+/*
+ * Split every target region into randomly-sized small regions
+ *
+ * This function splits every target region into random-sized small regions if
+ * current total number of the regions is equal or smaller than half of the
+ * user-specified maximum number of regions.  This is for maximizing the
+ * monitoring accuracy under the dynamically changeable access patterns.  If a
+ * split was unnecessarily made, later 'kdamond_merge_regions()' will revert
+ * it.
+ */
+static void kdamond_split_regions(struct damon_ctx *ctx)
+{
+	struct damon_target *t;
+	unsigned int nr_regions = 0;
+	static unsigned int last_nr_regions;
+	int nr_subregions = 2;
+
+	damon_for_each_target(t, ctx)
+		nr_regions += damon_nr_regions(t);
+
+	if (nr_regions > ctx->attrs.max_nr_regions / 2)
+		return;
+
+	/* Maybe the middle of the region has different access frequency */
+	if (last_nr_regions == nr_regions &&
+			nr_regions < ctx->attrs.max_nr_regions / 3)
+		nr_subregions = 3;
+
+	damon_for_each_target(t, ctx)
+		damon_split_regions_of(t, nr_subregions);
+
+	last_nr_regions = nr_regions;
+}
+
+/*
+ * Check whether it is time to check and apply the operations-related data
+ * structures.
+ *
+ * Returns true if it is.
+ */
+static bool kdamond_need_update_operations(struct damon_ctx *ctx)
+{
+	return damon_check_reset_time_interval(&ctx->last_ops_update,
+			ctx->attrs.ops_update_interval);
+}
+
+/*
+ * Check whether current monitoring should be stopped
+ *
+ * The monitoring is stopped when either the user requested to stop, or all
+ * monitoring targets are invalid.
+ *
+ * Returns true if need to stop current monitoring.
+ */
+static bool kdamond_need_stop(struct damon_ctx *ctx)
+{
+	struct damon_target *t;
+
+	if (kthread_should_stop())
+		return true;
+
+	if (!ctx->ops.target_valid)
+		return false;
+
+	damon_for_each_target(t, ctx) {
+		if (ctx->ops.target_valid(t))
+			return false;
+	}
+
+	return true;
+}
+
+static unsigned long damos_wmark_metric_value(enum damos_wmark_metric metric)
+{
+	struct sysinfo i;
+
+	switch (metric) {
+	case DAMOS_WMARK_FREE_MEM_RATE:
+		si_meminfo(&i);
+		return i.freeram * 1000 / i.totalram;
+	default:
+		break;
+	}
+	return -EINVAL;
+}
+
+/*
+ * Returns zero if the scheme is active.  Else, returns time to wait for next
+ * watermark check in micro-seconds.
+ */
+static unsigned long damos_wmark_wait_us(struct damos *scheme)
+{
+	unsigned long metric;
+
+	if (scheme->wmarks.metric == DAMOS_WMARK_NONE)
+		return 0;
+
+	metric = damos_wmark_metric_value(scheme->wmarks.metric);
+	/* higher than high watermark or lower than low watermark */
+	if (metric > scheme->wmarks.high || scheme->wmarks.low > metric) {
+		if (scheme->wmarks.activated)
+			pr_debug("deactivate a scheme (%d) for %s wmark\n",
+					scheme->action,
+					metric > scheme->wmarks.high ?
+					"high" : "low");
+		scheme->wmarks.activated = false;
+		return scheme->wmarks.interval;
+	}
+
+	/* inactive and higher than middle watermark */
+	if ((scheme->wmarks.high >= metric && metric >= scheme->wmarks.mid) &&
+			!scheme->wmarks.activated)
+		return scheme->wmarks.interval;
+
+	if (!scheme->wmarks.activated)
+		pr_debug("activate a scheme (%d)\n", scheme->action);
+	scheme->wmarks.activated = true;
+	return 0;
+}
+
+static void kdamond_usleep(unsigned long usecs)
+{
+	/* See Documentation/timers/timers-howto.rst for the thresholds */
+	if (usecs > 20 * USEC_PER_MSEC)
+		schedule_timeout_idle(usecs_to_jiffies(usecs));
+	else
+		usleep_idle_range(usecs, usecs + 1);
+}
+
+/* Returns negative error code if it's not activated but should return */
+static int kdamond_wait_activation(struct damon_ctx *ctx)
+{
+	struct damos *s;
+	unsigned long wait_time;
+	unsigned long min_wait_time = 0;
+	bool init_wait_time = false;
+
+	while (!kdamond_need_stop(ctx)) {
+		damon_for_each_scheme(s, ctx) {
+			wait_time = damos_wmark_wait_us(s);
+			if (!init_wait_time || wait_time < min_wait_time) {
+				init_wait_time = true;
+				min_wait_time = wait_time;
+			}
+		}
+		if (!min_wait_time)
+			return 0;
+
+		kdamond_usleep(min_wait_time);
+
+		if (ctx->callback.after_wmarks_check &&
+				ctx->callback.after_wmarks_check(ctx))
+			break;
+	}
+	return -EBUSY;
+}
+
+/*
+ * The monitoring daemon that runs as a kernel thread
+ */
+static int kdamond_fn(void *data)
+{
+	struct damon_ctx *ctx = data;
+	struct damon_target *t;
+	struct damon_region *r, *next;
+	unsigned int max_nr_accesses = 0;
+	unsigned long sz_limit = 0;
+
+	pr_debug("kdamond (%d) starts\n", current->pid);
+
+	complete(&ctx->kdamond_started);
+
+	if (ctx->ops.init)
+		ctx->ops.init(ctx);
+	if (ctx->callback.before_start && ctx->callback.before_start(ctx))
+		goto done;
+
+	sz_limit = damon_region_sz_limit(ctx);
+
+	while (!kdamond_need_stop(ctx)) {
+		if (kdamond_wait_activation(ctx))
+			break;
+
+		if (ctx->ops.prepare_access_checks)
+			ctx->ops.prepare_access_checks(ctx);
+		if (ctx->callback.after_sampling &&
+				ctx->callback.after_sampling(ctx))
+			break;
+
+		kdamond_usleep(ctx->attrs.sample_interval);
+
+		if (ctx->ops.check_accesses)
+			max_nr_accesses = ctx->ops.check_accesses(ctx);
+
+		if (kdamond_aggregate_interval_passed(ctx)) {
+			kdamond_merge_regions(ctx,
+					max_nr_accesses / 10,
+					sz_limit);
+			if (ctx->callback.after_aggregation &&
+					ctx->callback.after_aggregation(ctx))
+				break;
+			kdamond_apply_schemes(ctx);
+			kdamond_reset_aggregated(ctx);
+			kdamond_split_regions(ctx);
+			if (ctx->ops.reset_aggregated)
+				ctx->ops.reset_aggregated(ctx);
+		}
+
+		if (kdamond_need_update_operations(ctx)) {
+			if (ctx->ops.update)
+				ctx->ops.update(ctx);
+			sz_limit = damon_region_sz_limit(ctx);
+		}
+	}
+done:
+	damon_for_each_target(t, ctx) {
+		damon_for_each_region_safe(r, next, t)
+			damon_destroy_region(r, t);
+	}
+
+	if (ctx->callback.before_terminate)
+		ctx->callback.before_terminate(ctx);
+	if (ctx->ops.cleanup)
+		ctx->ops.cleanup(ctx);
+
+	pr_debug("kdamond (%d) finishes\n", current->pid);
+	mutex_lock(&ctx->kdamond_lock);
+	ctx->kdamond = NULL;
+	mutex_unlock(&ctx->kdamond_lock);
+
+	mutex_lock(&damon_lock);
+	nr_running_ctxs--;
+	if (!nr_running_ctxs && running_exclusive_ctxs)
+		running_exclusive_ctxs = false;
+	mutex_unlock(&damon_lock);
+
+	return 0;
+}
+
+/*
+ * struct damon_system_ram_region - System RAM resource address region of
+ *				    [@start, @end).
+ * @start:	Start address of the region (inclusive).
+ * @end:	End address of the region (exclusive).
+ */
+struct damon_system_ram_region {
+	unsigned long start;
+	unsigned long end;
+};
+
+static int walk_system_ram(struct resource *res, void *arg)
+{
+	struct damon_system_ram_region *a = arg;
+
+	if (a->end - a->start < resource_size(res)) {
+		a->start = res->start;
+		a->end = res->end;
+	}
+	return 0;
+}
+
+/*
+ * Find biggest 'System RAM' resource and store its start and end address in
+ * @start and @end, respectively.  If no System RAM is found, returns false.
+ */
+static bool damon_find_biggest_system_ram(unsigned long *start,
+						unsigned long *end)
+
+{
+	struct damon_system_ram_region arg = {};
+
+	walk_system_ram_res(0, ULONG_MAX, &arg, walk_system_ram);
+	if (arg.end <= arg.start)
+		return false;
+
+	*start = arg.start;
+	*end = arg.end;
+	return true;
+}
+
+/**
+ * damon_set_region_biggest_system_ram_default() - Set the region of the given
+ * monitoring target as requested, or biggest 'System RAM'.
+ * @t:		The monitoring target to set the region.
+ * @start:	The pointer to the start address of the region.
+ * @end:	The pointer to the end address of the region.
+ *
+ * This function sets the region of @t as requested by @start and @end.  If the
+ * values of @start and @end are zero, however, this function finds the biggest
+ * 'System RAM' resource and sets the region to cover the resource.  In the
+ * latter case, this function saves the start and end addresses of the resource
+ * in @start and @end, respectively.
+ *
+ * Return: 0 on success, negative error code otherwise.
+ */
+int damon_set_region_biggest_system_ram_default(struct damon_target *t,
+			unsigned long *start, unsigned long *end)
+{
+	struct damon_addr_range addr_range;
+
+	if (*start > *end)
+		return -EINVAL;
+
+	if (!*start && !*end &&
+		!damon_find_biggest_system_ram(start, end))
+		return -EINVAL;
+
+	addr_range.start = *start;
+	addr_range.end = *end;
+	return damon_set_regions(t, &addr_range, 1);
+}
+
+static int __init damon_init(void)
+{
+	damon_region_cache = KMEM_CACHE(damon_region, 0);
+	if (unlikely(!damon_region_cache)) {
+		pr_err("creating damon_region_cache fails\n");
+		return -ENOMEM;
+	}
+
+	return 0;
+}
+
+subsys_initcall(damon_init);
+
+#include "core-test.h"