+ mm-damon-lru_sort-fix-quota-status-loss-due-to-online-tunings.patch added to mm-hotfixes-unstable branch

+ mm-damon-lru_sort-fix-quota-status-loss-due-to-online-tunings.patch added to mm-hotfixes-unstable branch

[Andrew Morton]

The patch titled
     Subject: mm/damon/lru_sort: fix quota status loss due to online tunings
has been added to the -mm mm-hotfixes-unstable branch.  Its filename is
     mm-damon-lru_sort-fix-quota-status-loss-due-to-online-tunings.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-damon-lru_sort-fix-quota-status-loss-due-to-online-tunings.patch

This patch will later appear in the mm-hotfixes-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: SeongJae Park <sj@kernel.org>
Subject: mm/damon/lru_sort: fix quota status loss due to online tunings
Date: Fri, 16 Feb 2024 11:40:25 -0800

For online parameters change, DAMON_LRU_SORT creates new schemes based on
latest values of the parameters and replaces the old schemes with the new
one.  When creating it, the internal status of the quotas of the old
schemes is not preserved.  As a result, charging of the quota starts from
zero after the online tuning.  The data that collected to estimate the
throughput of the scheme's action is also reset, and therefore the
estimation should start from the scratch again.  Because the throughput
estimation is being used to convert the time quota to the effective size
quota, this could result in temporal time quota inaccuracy.  It would be
recovered over time, though.  In short, the quota accuracy could be
temporarily degraded after online parameters update.

Fix the problem by checking the case and copying the internal fields for
the status.

Link: https://lkml.kernel.org/r/20240216194025.9207-3-sj@kernel.org
Fixes: 40e983cca927 ("mm/damon: introduce DAMON-based LRU-lists Sorting")
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: <stable@vger.kernel.org>	[6.0+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/damon/lru_sort.c |   43 +++++++++++++++++++++++++++++++++++-------
 1 file changed, 36 insertions(+), 7 deletions(-)

--- a/mm/damon/lru_sort.c~mm-damon-lru_sort-fix-quota-status-loss-due-to-online-tunings
+++ a/mm/damon/lru_sort.c
@@ -185,9 +185,21 @@ static struct damos *damon_lru_sort_new_
 	return damon_lru_sort_new_scheme(&pattern, DAMOS_LRU_DEPRIO);
 }
 
+static void damon_lru_sort_copy_quota_status(struct damos_quota *dst,
+		struct damos_quota *src)
+{
+	dst->total_charged_sz = src->total_charged_sz;
+	dst->total_charged_ns = src->total_charged_ns;
+	dst->charged_sz = src->charged_sz;
+	dst->charged_from = src->charged_from;
+	dst->charge_target_from = src->charge_target_from;
+	dst->charge_addr_from = src->charge_addr_from;
+}
+
 static int damon_lru_sort_apply_parameters(void)
 {
-	struct damos *scheme;
+	struct damos *scheme, *hot_scheme, *cold_scheme;
+	struct damos *old_hot_scheme = NULL, *old_cold_scheme = NULL;
 	unsigned int hot_thres, cold_thres;
 	int err = 0;
 
@@ -195,18 +207,35 @@ static int damon_lru_sort_apply_paramete
 	if (err)
 		return err;
 
+	damon_for_each_scheme(scheme, ctx) {
+		if (!old_hot_scheme) {
+			old_hot_scheme = scheme;
+			continue;
+		}
+		old_cold_scheme = scheme;
+	}
+
 	hot_thres = damon_max_nr_accesses(&damon_lru_sort_mon_attrs) *
 		hot_thres_access_freq / 1000;
-	scheme = damon_lru_sort_new_hot_scheme(hot_thres);
-	if (!scheme)
+	hot_scheme = damon_lru_sort_new_hot_scheme(hot_thres);
+	if (!hot_scheme)
 		return -ENOMEM;
-	damon_set_schemes(ctx, &scheme, 1);
+	if (old_hot_scheme)
+		damon_lru_sort_copy_quota_status(&hot_scheme->quota,
+				&old_hot_scheme->quota);
 
 	cold_thres = cold_min_age / damon_lru_sort_mon_attrs.aggr_interval;
-	scheme = damon_lru_sort_new_cold_scheme(cold_thres);
-	if (!scheme)
+	cold_scheme = damon_lru_sort_new_cold_scheme(cold_thres);
+	if (!cold_scheme) {
+		damon_destroy_scheme(hot_scheme);
 		return -ENOMEM;
-	damon_add_scheme(ctx, scheme);
+	}
+	if (old_cold_scheme)
+		damon_lru_sort_copy_quota_status(&cold_scheme->quota,
+				&old_cold_scheme->quota);
+
+	damon_set_schemes(ctx, &hot_scheme, 1);
+	damon_add_scheme(ctx, cold_scheme);
 
 	return damon_set_region_biggest_system_ram_default(target,
 					&monitor_region_start,
_

Patches currently in -mm which might be from sj@kernel.org are

mm-damon-core-check-apply-interval-in-damon_do_apply_schemes.patch
mm-damon-sysfs-schemes-handle-schemes-sysfs-dir-removal-before-commit_schemes_quota_goals.patch
mm-damon-reclaim-fix-quota-stauts-loss-due-to-online-tunings.patch
mm-damon-lru_sort-fix-quota-status-loss-due-to-online-tunings.patch
docs-admin-guide-mm-damon-usage-use-sysfs-interface-for-tracepoints-example.patch
mm-damon-rename-config_damon_dbgfs-to-damon_dbgfs_deprecated.patch
mm-damon-dbgfs-implement-deprecation-notice-file.patch
mm-damon-dbgfs-make-debugfs-interface-deprecation-message-a-macro.patch
docs-admin-guide-mm-damon-usage-document-deprecated-file-of-damon-debugfs-interface.patch
selftets-damon-prepare-for-monitor_on-file-renaming.patch
mm-damon-dbgfs-rename-monitor_on-file-to-monitor_on_deprecated.patch
docs-admin-guide-mm-damon-usage-update-for-monitor_on-renaming.patch
docs-translations-damon-usage-update-for-monitor_on-renaming.patch
mm-damon-sysfs-handle-state-file-inputs-for-every-sampling-interval-if-possible.patch
selftests-damon-_damon_sysfs-support-damos-quota.patch
selftests-damon-_damon_sysfs-support-damos-stats.patch
selftests-damon-_damon_sysfs-support-damos-apply-interval.patch
selftests-damon-add-a-test-for-damos-quota.patch
selftests-damon-add-a-test-for-damos-apply-intervals.patch
selftests-damon-add-a-test-for-a-race-between-target_ids_read-and-dbgfs_before_terminate.patch
selftests-damon-add-a-test-for-the-pid-leak-of-dbgfs_target_ids_write.patch
selftests-damon-_chk_dependency-get-debugfs-mount-point-from-proc-mounts.patch
docs-mm-damon-maintainer-profile-fix-reference-links-for-mm-stable-tree.patch
docs-mm-damon-move-the-list-of-damos-actions-to-design-doc.patch
docs-mm-damon-move-damon-operation-sets-list-from-the-usage-to-the-design-document.patch
docs-mm-damon-move-monitoring-target-regions-setup-detail-from-the-usage-to-the-design-document.patch
docs-admin-guide-mm-damon-usage-fix-wrong-quotas-diabling-condition.patch
mm-damon-core-set-damos_quota-esz-as-public-field-and-document.patch
mm-damon-sysfs-schemes-implement-quota-effective_bytes-file.patch
mm-damon-sysfs-implement-a-kdamond-command-for-updating-schemes-effective-quotas.patch
docs-abi-damon-document-effective_bytes-sysfs-file.patch
docs-admin-guide-mm-damon-usage-document-effective_bytes-file.patch
mm-damon-move-comments-and-fields-for-damos-quota-prioritization-to-the-end.patch
mm-damon-core-split-out-quota-goal-related-fields-to-a-struct.patch
mm-damon-core-add-multiple-goals-per-damos_quota-and-helpers-for-those.patch
mm-damon-sysfs-use-only-quota-goals.patch
mm-damon-core-remove-goal-field-of-damos_quota.patch
mm-damon-core-let-goal-specified-with-only-target-and-current-values.patch
mm-damon-core-support-multiple-metrics-for-quota-goal.patch
mm-damon-core-implement-psi-metric-damos-quota-goal.patch
mm-damon-sysfs-schemes-support-psi-based-quota-auto-tune.patch
docs-mm-damon-design-document-quota-goal-self-tuning.patch
docs-abi-damon-document-quota-goal-metric-file.patch
docs-admin-guide-mm-damon-usage-document-quota-goal-metric-file.patch
mm-damon-reclaim-implement-user-feedback-driven-quota-auto-tuning.patch
mm-damon-reclaim-implement-memory-psi-driven-quota-self-tuning.patch
docs-admin-guide-mm-damon-reclaim-document-auto-tuning-parameters.patch