mm/damon/lru_sort: add monitoring intervals auto-tuning parameter

DAMON monitoring intervals tuning was crucial for every DAMON use case. 
Now there are a tuning guideline and an automated intervals tuning
feature.  DAMON_LRU_SORT is still using manual control of intervals.  Add
a module parameter for utilizing the auto-tuning feature with a suggested
auto-tuning parameters.

Link: https://lkml.kernel.org/r/20260113152717.70459-11-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Acked-by: wang lian <lianux.mm@gmail.com>
Cc: David Hildenbrand <david@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

1 files changed, 27 insertions, 3 deletions

diff --git a/mm/damon/lru_sort.c b/mm/damon/lru_sort.c
index 8af97642912a..8296f984b428 100644
--- a/mm/damon/lru_sort.c
+++ b/mm/damon/lru_sort.c
@@ -56,6 +56,20 @@ static unsigned long active_mem_bp __read_mostly;
 module_param(active_mem_bp, ulong, 0600);
 
 /*
+ * Auto-tune monitoring intervals.
+ *
+ * If this parameter is set as ``Y``, DAMON_LRU_SORT automatically tunes
+ * DAMON's sampling and aggregation intervals.  The auto-tuning aims to capture
+ * meaningful amount of access events in each DAMON-snapshot, while keeping the
+ * sampling interval 5 milliseconds in minimum, and 10 seconds in maximum.
+ * Setting this as ``N`` disables the auto-tuning.
+ *
+ * Disabled by default.
+ */
+static bool autotune_monitoring_intervals __read_mostly;
+module_param(autotune_monitoring_intervals, bool, 0600);
+
+/*
  * Filter [non-]young pages accordingly for LRU [de]prioritizations.
  *
  * If this is set, check page level access (youngness) once again before each
@@ -268,6 +282,7 @@ static int damon_lru_sort_apply_parameters(void)
 {
 	struct damon_ctx *param_ctx;
 	struct damon_target *param_target;
+	struct damon_attrs attrs;
 	struct damos *hot_scheme, *cold_scheme;
 	unsigned int hot_thres, cold_thres;
 	int err;
@@ -290,18 +305,27 @@ static int damon_lru_sort_apply_parameters(void)
 		goto out;
 	}
 
-	err = damon_set_attrs(param_ctx, &damon_lru_sort_mon_attrs);
+	attrs = damon_lru_sort_mon_attrs;
+	if (autotune_monitoring_intervals) {
+		attrs.sample_interval = 5000;
+		attrs.aggr_interval = 100000;
+		attrs.intervals_goal.access_bp = 40;
+		attrs.intervals_goal.aggrs = 3;
+		attrs.intervals_goal.min_sample_us = 5000;
+		attrs.intervals_goal.max_sample_us = 10 * 1000 * 1000;
+	}
+	err = damon_set_attrs(param_ctx, &attrs);
 	if (err)
 		goto out;
 
 	err = -ENOMEM;
-	hot_thres = damon_max_nr_accesses(&damon_lru_sort_mon_attrs) *
+	hot_thres = damon_max_nr_accesses(&attrs) *
 		hot_thres_access_freq / 1000;
 	hot_scheme = damon_lru_sort_new_hot_scheme(hot_thres);
 	if (!hot_scheme)
 		goto out;
 
-	cold_thres = cold_min_age / damon_lru_sort_mon_attrs.aggr_interval;
+	cold_thres = cold_min_age / attrs.aggr_interval;
 	cold_scheme = damon_lru_sort_new_cold_scheme(cold_thres);
 	if (!cold_scheme) {
 		damon_destroy_scheme(hot_scheme);