Merge tag 'mm-stable-2023-11-01-14-33' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

Pull MM updates from Andrew Morton:
 "Many singleton patches against the MM code. The patch series which are
  included in this merge do the following:

   - Kemeng Shi has contributed some compation maintenance work in the
     series 'Fixes and cleanups to compaction'

   - Joel Fernandes has a patchset ('Optimize mremap during mutual
     alignment within PMD') which fixes an obscure issue with mremap()'s
     pagetable handling during a subsequent exec(), based upon an
     implementation which Linus suggested

   - More DAMON/DAMOS maintenance and feature work from SeongJae Park i
     the following patch series:

	mm/damon: misc fixups for documents, comments and its tracepoint
	mm/damon: add a tracepoint for damos apply target regions
	mm/damon: provide pseudo-moving sum based access rate
	mm/damon: implement DAMOS apply intervals
	mm/damon/core-test: Fix memory leaks in core-test
	mm/damon/sysfs-schemes: Do DAMOS tried regions update for only one apply interval

   - In the series 'Do not try to access unaccepted memory' Adrian
     Hunter provides some fixups for the recently-added 'unaccepted
     memory' feature. To increase the feature's checking coverage. 'Plug
     a few gaps where RAM is exposed without checking if it is
     unaccepted memory'

   - In the series 'cleanups for lockless slab shrink' Qi Zheng has done
     some maintenance work which is preparation for the lockless slab
     shrinking code

   - Qi Zheng has redone the earlier (and reverted) attempt to make slab
     shrinking lockless in the series 'use refcount+RCU method to
     implement lockless slab shrink'

   - David Hildenbrand contributes some maintenance work for the rmap
     code in the series 'Anon rmap cleanups'

   - Kefeng Wang does more folio conversions and some maintenance work
     in the migration code. Series 'mm: migrate: more folio conversion
     and unification'

   - Matthew Wilcox has fixed an issue in the buffer_head code which was
     causing long stalls under some heavy memory/IO loads. Some cleanups
     were added on the way. Series 'Add and use bdev_getblk()'

   - In the series 'Use nth_page() in place of direct struct page
     manipulation' Zi Yan has fixed a potential issue with the direct
     manipulation of hugetlb page frames

   - In the series 'mm: hugetlb: Skip initialization of gigantic tail
     struct pages if freed by HVO' has improved our handling of gigantic
     pages in the hugetlb vmmemmep optimizaton code. This provides
     significant boot time improvements when significant amounts of
     gigantic pages are in use

   - Matthew Wilcox has sent the series 'Small hugetlb cleanups' - code
     rationalization and folio conversions in the hugetlb code

   - Yin Fengwei has improved mlock()'s handling of large folios in the
     series 'support large folio for mlock'

   - In the series 'Expose swapcache stat for memcg v1' Liu Shixin has
     added statistics for memcg v1 users which are available (and
     useful) under memcg v2

   - Florent Revest has enhanced the MDWE (Memory-Deny-Write-Executable)
     prctl so that userspace may direct the kernel to not automatically
     propagate the denial to child processes. The series is named 'MDWE
     without inheritance'

   - Kefeng Wang has provided the series 'mm: convert numa balancing
     functions to use a folio' which does what it says

   - In the series 'mm/ksm: add fork-exec support for prctl' Stefan
     Roesch makes is possible for a process to propagate KSM treatment
     across exec()

   - Huang Ying has enhanced memory tiering's calculation of memory
     distances. This is used to permit the dax/kmem driver to use 'high
     bandwidth memory' in addition to Optane Data Center Persistent
     Memory Modules (DCPMM). The series is named 'memory tiering:
     calculate abstract distance based on ACPI HMAT'

   - In the series 'Smart scanning mode for KSM' Stefan Roesch has
     optimized KSM by teaching it to retain and use some historical
     information from previous scans

   - Yosry Ahmed has fixed some inconsistencies in memcg statistics in
     the series 'mm: memcg: fix tracking of pending stats updates
     values'

   - In the series 'Implement IOCTL to get and optionally clear info
     about PTEs' Peter Xu has added an ioctl to /proc/<pid>/pagemap
     which permits us to atomically read-then-clear page softdirty
     state. This is mainly used by CRIU

   - Hugh Dickins contributed the series 'shmem,tmpfs: general
     maintenance', a bunch of relatively minor maintenance tweaks to
     this code

   - Matthew Wilcox has increased the use of the VMA lock over
     file-backed page faults in the series 'Handle more faults under the
     VMA lock'. Some rationalizations of the fault path became possible
     as a result

   - In the series 'mm/rmap: convert page_move_anon_rmap() to
     folio_move_anon_rmap()' David Hildenbrand has implemented some
     cleanups and folio conversions

   - In the series 'various improvements to the GUP interface' Lorenzo
     Stoakes has simplified and improved the GUP interface with an eye
     to providing groundwork for future improvements

   - Andrey Konovalov has sent along the series 'kasan: assorted fixes
     and improvements' which does those things

   - Some page allocator maintenance work from Kemeng Shi in the series
     'Two minor cleanups to break_down_buddy_pages'

   - In thes series 'New selftest for mm' Breno Leitao has developed
     another MM self test which tickles a race we had between madvise()
     and page faults

   - In the series 'Add folio_end_read' Matthew Wilcox provides cleanups
     and an optimization to the core pagecache code

   - Nhat Pham has added memcg accounting for hugetlb memory in the
     series 'hugetlb memcg accounting'

   - Cleanups and rationalizations to the pagemap code from Lorenzo
     Stoakes, in the series 'Abstract vma_merge() and split_vma()'

   - Audra Mitchell has fixed issues in the procfs page_owner code's new
     timestamping feature which was causing some misbehaviours. In the
     series 'Fix page_owner's use of free timestamps'

   - Lorenzo Stoakes has fixed the handling of new mappings of sealed
     files in the series 'permit write-sealed memfd read-only shared
     mappings'

   - Mike Kravetz has optimized the hugetlb vmemmap optimization in the
     series 'Batch hugetlb vmemmap modification operations'

   - Some buffer_head folio conversions and cleanups from Matthew Wilcox
     in the series 'Finish the create_empty_buffers() transition'

   - As a page allocator performance optimization Huang Ying has added
     automatic tuning to the allocator's per-cpu-pages feature, in the
     series 'mm: PCP high auto-tuning'

   - Roman Gushchin has contributed the patchset 'mm: improve
     performance of accounted kernel memory allocations' which improves
     their performance by ~30% as measured by a micro-benchmark

   - folio conversions from Kefeng Wang in the series 'mm: convert page
     cpupid functions to folios'

   - Some kmemleak fixups in Liu Shixin's series 'Some bugfix about
     kmemleak'

   - Qi Zheng has improved our handling of memoryless nodes by keeping
     them off the allocation fallback list. This is done in the series
     'handle memoryless nodes more appropriately'

   - khugepaged conversions from Vishal Moola in the series 'Some
     khugepaged folio conversions'"

[ bcachefs conflicts with the dynamically allocated shrinkers have been
  resolved as per Stephen Rothwell in

     https://lore.kernel.org/all/20230913093553.4290421e@canb.auug.org.au/

  with help from Qi Zheng.

  The clone3 test filtering conflict was half-arsed by yours truly ]

* tag 'mm-stable-2023-11-01-14-33' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (406 commits)
  mm/damon/sysfs: update monitoring target regions for online input commit
  mm/damon/sysfs: remove requested targets when online-commit inputs
  selftests: add a sanity check for zswap
  Documentation: maple_tree: fix word spelling error
  mm/vmalloc: fix the unchecked dereference warning in vread_iter()
  zswap: export compression failure stats
  Documentation: ubsan: drop "the" from article title
  mempolicy: migration attempt to match interleave nodes
  mempolicy: mmap_lock is not needed while migrating folios
  mempolicy: alloc_pages_mpol() for NUMA policy without vma
  mm: add page_rmappable_folio() wrapper
  mempolicy: remove confusing MPOL_MF_LAZY dead code
  mempolicy: mpol_shared_policy_init() without pseudo-vma
  mempolicy trivia: use pgoff_t in shared mempolicy tree
  mempolicy trivia: slightly more consistent naming
  mempolicy trivia: delete those ancient pr_debug()s
  mempolicy: fix migrate_pages(2) syscall return nr_failed
  kernfs: drop shared NUMA mempolicy hooks
  hugetlbfs: drop shared NUMA mempolicy pretence
  mm/damon/sysfs-test: add a unit test for damon_sysfs_set_targets()
  ...

1 files changed, 226 insertions, 69 deletions

diff --git a/mm/damon/core.c b/mm/damon/core.c
index bcd2bd9d6c10..aa2dc7087cd9 100644
--- a/mm/damon/core.c
+++ b/mm/damon/core.c
@@ -128,6 +128,7 @@ struct damon_region *damon_new_region(unsigned long start, unsigned long end)
 	region->ar.start = start;
 	region->ar.end = end;
 	region->nr_accesses = 0;
+	region->nr_accesses_bp = 0;
 	INIT_LIST_HEAD(&region->list);
 
 	region->age = 0;
@@ -312,7 +313,9 @@ static struct damos_quota *damos_quota_init_priv(struct damos_quota *quota)
 }
 
 struct damos *damon_new_scheme(struct damos_access_pattern *pattern,
-			enum damos_action action, struct damos_quota *quota,
+			enum damos_action action,
+			unsigned long apply_interval_us,
+			struct damos_quota *quota,
 			struct damos_watermarks *wmarks)
 {
 	struct damos *scheme;
@@ -322,6 +325,13 @@ struct damos *damon_new_scheme(struct damos_access_pattern *pattern,
 		return NULL;
 	scheme->pattern = *pattern;
 	scheme->action = action;
+	scheme->apply_interval_us = apply_interval_us;
+	/*
+	 * next_apply_sis will be set when kdamond starts.  While kdamond is
+	 * running, it will also updated when it is added to the DAMON context,
+	 * or damon_attrs are updated.
+	 */
+	scheme->next_apply_sis = 0;
 	INIT_LIST_HEAD(&scheme->filters);
 	scheme->stat = (struct damos_stat){};
 	INIT_LIST_HEAD(&scheme->list);
@@ -334,9 +344,21 @@ struct damos *damon_new_scheme(struct damos_access_pattern *pattern,
 	return scheme;
 }
 
+static void damos_set_next_apply_sis(struct damos *s, struct damon_ctx *ctx)
+{
+	unsigned long sample_interval = ctx->attrs.sample_interval ?
+		ctx->attrs.sample_interval : 1;
+	unsigned long apply_interval = s->apply_interval_us ?
+		s->apply_interval_us : ctx->attrs.aggr_interval;
+
+	s->next_apply_sis = ctx->passed_sample_intervals +
+		apply_interval / sample_interval;
+}
+
 void damon_add_scheme(struct damon_ctx *ctx, struct damos *s)
 {
 	list_add_tail(&s->list, &ctx->schemes);
+	damos_set_next_apply_sis(s, ctx);
 }
 
 static void damon_del_scheme(struct damos *s)
@@ -427,8 +449,10 @@ struct damon_ctx *damon_new_ctx(void)
 	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;
+	ctx->passed_sample_intervals = 0;
+	/* These will be set from kdamond_init_intervals_sis() */
+	ctx->next_aggregation_sis = 0;
+	ctx->next_ops_update_sis = 0;
 
 	mutex_init(&ctx->kdamond_lock);
 
@@ -476,20 +500,14 @@ static unsigned int damon_age_for_new_attrs(unsigned int age,
 static unsigned int damon_accesses_bp_to_nr_accesses(
 		unsigned int accesses_bp, struct damon_attrs *attrs)
 {
-	unsigned int max_nr_accesses =
-		attrs->aggr_interval / attrs->sample_interval;
-
-	return accesses_bp * max_nr_accesses / 10000;
+	return accesses_bp * damon_max_nr_accesses(attrs) / 10000;
 }
 
 /* convert nr_accesses to access ratio in bp (per 10,000) */
 static unsigned int damon_nr_accesses_to_accesses_bp(
 		unsigned int nr_accesses, struct damon_attrs *attrs)
 {
-	unsigned int max_nr_accesses =
-		attrs->aggr_interval / attrs->sample_interval;
-
-	return nr_accesses * 10000 / max_nr_accesses;
+	return nr_accesses * 10000 / damon_max_nr_accesses(attrs);
 }
 
 static unsigned int damon_nr_accesses_for_new_attrs(unsigned int nr_accesses,
@@ -506,6 +524,7 @@ static void damon_update_monitoring_result(struct damon_region *r,
 {
 	r->nr_accesses = damon_nr_accesses_for_new_attrs(r->nr_accesses,
 			old_attrs, new_attrs);
+	r->nr_accesses_bp = r->nr_accesses * 10000;
 	r->age = damon_age_for_new_attrs(r->age, old_attrs, new_attrs);
 }
 
@@ -541,13 +560,21 @@ static void damon_update_monitoring_results(struct damon_ctx *ctx,
  * @ctx:		monitoring context
  * @attrs:		monitoring attributes
  *
- * This function should not be called while the kdamond is running.
+ * This function should be called while the kdamond is not running, or an
+ * access check results aggregation is not ongoing (e.g., from
+ * &struct damon_callback->after_aggregation or
+ * &struct damon_callback->after_wmarks_check callbacks).
+ *
  * 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)
 {
+	unsigned long sample_interval = attrs->sample_interval ?
+		attrs->sample_interval : 1;
+	struct damos *s;
+
 	if (attrs->min_nr_regions < 3)
 		return -EINVAL;
 	if (attrs->min_nr_regions > attrs->max_nr_regions)
@@ -555,8 +582,17 @@ int damon_set_attrs(struct damon_ctx *ctx, struct damon_attrs *attrs)
 	if (attrs->sample_interval > attrs->aggr_interval)
 		return -EINVAL;
 
+	ctx->next_aggregation_sis = ctx->passed_sample_intervals +
+		attrs->aggr_interval / sample_interval;
+	ctx->next_ops_update_sis = ctx->passed_sample_intervals +
+		attrs->ops_update_interval / sample_interval;
+
 	damon_update_monitoring_results(ctx, attrs);
 	ctx->attrs = *attrs;
+
+	damon_for_each_scheme(s, ctx)
+		damos_set_next_apply_sis(s, ctx);
+
 	return 0;
 }
 
@@ -729,38 +765,6 @@ int damon_stop(struct damon_ctx **ctxs, int nr_ctxs)
 }
 
 /*
- * 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)
@@ -772,7 +776,7 @@ static void kdamond_reset_aggregated(struct damon_ctx *c)
 		struct damon_region *r;
 
 		damon_for_each_region(r, t) {
-			trace_damon_aggregated(t, ti, r, damon_nr_regions(t));
+			trace_damon_aggregated(ti, r, damon_nr_regions(t));
 			r->last_nr_accesses = r->nr_accesses;
 			r->nr_accesses = 0;
 		}
@@ -786,12 +790,13 @@ static void damon_split_region_at(struct damon_target *t,
 static bool __damos_valid_target(struct damon_region *r, struct damos *s)
 {
 	unsigned long sz;
+	unsigned int nr_accesses = r->nr_accesses_bp / 10000;
 
 	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_nr_accesses <= nr_accesses &&
+		nr_accesses <= s->pattern.max_nr_accesses &&
 		s->pattern.min_age_region <= r->age &&
 		r->age <= s->pattern.max_age_region;
 }
@@ -946,6 +951,33 @@ static void damos_apply_scheme(struct damon_ctx *c, struct damon_target *t,
 	struct timespec64 begin, end;
 	unsigned long sz_applied = 0;
 	int err = 0;
+	/*
+	 * We plan to support multiple context per kdamond, as DAMON sysfs
+	 * implies with 'nr_contexts' file.  Nevertheless, only single context
+	 * per kdamond is supported for now.  So, we can simply use '0' context
+	 * index here.
+	 */
+	unsigned int cidx = 0;
+	struct damos *siter;		/* schemes iterator */
+	unsigned int sidx = 0;
+	struct damon_target *titer;	/* targets iterator */
+	unsigned int tidx = 0;
+	bool do_trace = false;
+
+	/* get indices for trace_damos_before_apply() */
+	if (trace_damos_before_apply_enabled()) {
+		damon_for_each_scheme(siter, c) {
+			if (siter == s)
+				break;
+			sidx++;
+		}
+		damon_for_each_target(titer, c) {
+			if (titer == t)
+				break;
+			tidx++;
+		}
+		do_trace = true;
+	}
 
 	if (c->ops.apply_scheme) {
 		if (quota->esz && quota->charged_sz + sz > quota->esz) {
@@ -960,8 +992,11 @@ static void damos_apply_scheme(struct damon_ctx *c, struct damon_target *t,
 		ktime_get_coarse_ts64(&begin);
 		if (c->callback.before_damos_apply)
 			err = c->callback.before_damos_apply(c, t, r, s);
-		if (!err)
+		if (!err) {
+			trace_damos_before_apply(cidx, sidx, tidx, r,
+					damon_nr_regions(t), do_trace);
 			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);
@@ -1079,14 +1114,29 @@ static void kdamond_apply_schemes(struct damon_ctx *c)
 	struct damon_target *t;
 	struct damon_region *r, *next_r;
 	struct damos *s;
+	unsigned long sample_interval = c->attrs.sample_interval ?
+		c->attrs.sample_interval : 1;
+	bool has_schemes_to_apply = false;
 
 	damon_for_each_scheme(s, c) {
+		if (c->passed_sample_intervals != s->next_apply_sis)
+			continue;
+
+		s->next_apply_sis +=
+			(s->apply_interval_us ? s->apply_interval_us :
+			 c->attrs.aggr_interval) / sample_interval;
+
 		if (!s->wmarks.activated)
 			continue;
 
+		has_schemes_to_apply = true;
+
 		damos_adjust_quota(c, s);
 	}
 
+	if (!has_schemes_to_apply)
+		return;
+
 	damon_for_each_target(t, c) {
 		damon_for_each_region_safe(r, next_r, t)
 			damon_do_apply_schemes(c, t, r);
@@ -1103,6 +1153,7 @@ static void damon_merge_two_regions(struct damon_target *t,
 
 	l->nr_accesses = (l->nr_accesses * sz_l + r->nr_accesses * sz_r) /
 			(sz_l + sz_r);
+	l->nr_accesses_bp = l->nr_accesses * 10000;
 	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);
@@ -1174,6 +1225,7 @@ static void damon_split_region_at(struct damon_target *t,
 
 	new->age = r->age;
 	new->last_nr_accesses = r->last_nr_accesses;
+	new->nr_accesses_bp = r->nr_accesses_bp;
 
 	damon_insert_region(new, r, damon_next_region(r), t);
 }
@@ -1241,18 +1293,6 @@ static void kdamond_split_regions(struct damon_ctx *ctx)
 }
 
 /*
- * 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
@@ -1280,12 +1320,10 @@ static bool kdamond_need_stop(struct damon_ctx *ctx)
 
 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;
+		return global_zone_page_state(NR_FREE_PAGES) * 1000 /
+		       totalram_pages();
 	default:
 		break;
 	}
@@ -1363,6 +1401,25 @@ static int kdamond_wait_activation(struct damon_ctx *ctx)
 	return -EBUSY;
 }
 
+static void kdamond_init_intervals_sis(struct damon_ctx *ctx)
+{
+	unsigned long sample_interval = ctx->attrs.sample_interval ?
+		ctx->attrs.sample_interval : 1;
+	unsigned long apply_interval;
+	struct damos *scheme;
+
+	ctx->passed_sample_intervals = 0;
+	ctx->next_aggregation_sis = ctx->attrs.aggr_interval / sample_interval;
+	ctx->next_ops_update_sis = ctx->attrs.ops_update_interval /
+		sample_interval;
+
+	damon_for_each_scheme(scheme, ctx) {
+		apply_interval = scheme->apply_interval_us ?
+			scheme->apply_interval_us : ctx->attrs.aggr_interval;
+		scheme->next_apply_sis = apply_interval / sample_interval;
+	}
+}
+
 /*
  * The monitoring daemon that runs as a kernel thread
  */
@@ -1376,6 +1433,8 @@ static int kdamond_fn(void *data)
 
 	pr_debug("kdamond (%d) starts\n", current->pid);
 
+	kdamond_init_intervals_sis(ctx);
+
 	if (ctx->ops.init)
 		ctx->ops.init(ctx);
 	if (ctx->callback.before_start && ctx->callback.before_start(ctx))
@@ -1384,6 +1443,17 @@ static int kdamond_fn(void *data)
 	sz_limit = damon_region_sz_limit(ctx);
 
 	while (!kdamond_need_stop(ctx)) {
+		/*
+		 * ctx->attrs and ctx->next_{aggregation,ops_update}_sis could
+		 * be changed from after_wmarks_check() or after_aggregation()
+		 * callbacks.  Read the values here, and use those for this
+		 * iteration.  That is, damon_set_attrs() updated new values
+		 * are respected from next iteration.
+		 */
+		unsigned long next_aggregation_sis = ctx->next_aggregation_sis;
+		unsigned long next_ops_update_sis = ctx->next_ops_update_sis;
+		unsigned long sample_interval = ctx->attrs.sample_interval;
+
 		if (kdamond_wait_activation(ctx))
 			break;
 
@@ -1393,27 +1463,44 @@ static int kdamond_fn(void *data)
 				ctx->callback.after_sampling(ctx))
 			break;
 
-		kdamond_usleep(ctx->attrs.sample_interval);
+		kdamond_usleep(sample_interval);
+		ctx->passed_sample_intervals++;
 
 		if (ctx->ops.check_accesses)
 			max_nr_accesses = ctx->ops.check_accesses(ctx);
 
-		if (kdamond_aggregate_interval_passed(ctx)) {
+		if (ctx->passed_sample_intervals == next_aggregation_sis) {
 			kdamond_merge_regions(ctx,
 					max_nr_accesses / 10,
 					sz_limit);
 			if (ctx->callback.after_aggregation &&
 					ctx->callback.after_aggregation(ctx))
 				break;
-			if (!list_empty(&ctx->schemes))
-				kdamond_apply_schemes(ctx);
+		}
+
+		/*
+		 * do kdamond_apply_schemes() after kdamond_merge_regions() if
+		 * possible, to reduce overhead
+		 */
+		if (!list_empty(&ctx->schemes))
+			kdamond_apply_schemes(ctx);
+
+		sample_interval = ctx->attrs.sample_interval ?
+			ctx->attrs.sample_interval : 1;
+		if (ctx->passed_sample_intervals == next_aggregation_sis) {
+			ctx->next_aggregation_sis = next_aggregation_sis +
+				ctx->attrs.aggr_interval / sample_interval;
+
 			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->passed_sample_intervals == next_ops_update_sis) {
+			ctx->next_ops_update_sis = next_ops_update_sis +
+				ctx->attrs.ops_update_interval /
+				sample_interval;
 			if (ctx->ops.update)
 				ctx->ops.update(ctx);
 			sz_limit = damon_region_sz_limit(ctx);
@@ -1517,6 +1604,76 @@ int damon_set_region_biggest_system_ram_default(struct damon_target *t,
 	return damon_set_regions(t, &addr_range, 1);
 }
 
+/*
+ * damon_moving_sum() - Calculate an inferred moving sum value.
+ * @mvsum:	Inferred sum of the last @len_window values.
+ * @nomvsum:	Non-moving sum of the last discrete @len_window window values.
+ * @len_window:	The number of last values to take care of.
+ * @new_value:	New value that will be added to the pseudo moving sum.
+ *
+ * Moving sum (moving average * window size) is good for handling noise, but
+ * the cost of keeping past values can be high for arbitrary window size.  This
+ * function implements a lightweight pseudo moving sum function that doesn't
+ * keep the past window values.
+ *
+ * It simply assumes there was no noise in the past, and get the no-noise
+ * assumed past value to drop from @nomvsum and @len_window.  @nomvsum is a
+ * non-moving sum of the last window.  For example, if @len_window is 10 and we
+ * have 25 values, @nomvsum is the sum of the 11th to 20th values of the 25
+ * values.  Hence, this function simply drops @nomvsum / @len_window from
+ * given @mvsum and add @new_value.
+ *
+ * For example, if @len_window is 10 and @nomvsum is 50, the last 10 values for
+ * the last window could be vary, e.g., 0, 10, 0, 10, 0, 10, 0, 0, 0, 20.  For
+ * calculating next moving sum with a new value, we should drop 0 from 50 and
+ * add the new value.  However, this function assumes it got value 5 for each
+ * of the last ten times.  Based on the assumption, when the next value is
+ * measured, it drops the assumed past value, 5 from the current sum, and add
+ * the new value to get the updated pseduo-moving average.
+ *
+ * This means the value could have errors, but the errors will be disappeared
+ * for every @len_window aligned calls.  For example, if @len_window is 10, the
+ * pseudo moving sum with 11th value to 19th value would have an error.  But
+ * the sum with 20th value will not have the error.
+ *
+ * Return: Pseudo-moving average after getting the @new_value.
+ */
+static unsigned int damon_moving_sum(unsigned int mvsum, unsigned int nomvsum,
+		unsigned int len_window, unsigned int new_value)
+{
+	return mvsum - nomvsum / len_window + new_value;
+}
+
+/**
+ * damon_update_region_access_rate() - Update the access rate of a region.
+ * @r:		The DAMON region to update for its access check result.
+ * @accessed:	Whether the region has accessed during last sampling interval.
+ * @attrs:	The damon_attrs of the DAMON context.
+ *
+ * Update the access rate of a region with the region's last sampling interval
+ * access check result.
+ *
+ * Usually this will be called by &damon_operations->check_accesses callback.
+ */
+void damon_update_region_access_rate(struct damon_region *r, bool accessed,
+		struct damon_attrs *attrs)
+{
+	unsigned int len_window = 1;
+
+	/*
+	 * sample_interval can be zero, but cannot be larger than
+	 * aggr_interval, owing to validation of damon_set_attrs().
+	 */
+	if (attrs->sample_interval)
+		len_window = damon_max_nr_accesses(attrs);
+	r->nr_accesses_bp = damon_moving_sum(r->nr_accesses_bp,
+			r->last_nr_accesses * 10000, len_window,
+			accessed ? 10000 : 0);
+
+	if (accessed)
+		r->nr_accesses++;
+}
+
 static int __init damon_init(void)
 {
 	damon_region_cache = KMEM_CACHE(damon_region, 0);