[PATCH 10/11] mm/damon/lru_sort: add monitoring intervals auto-tuning parameter

[SeongJae Park <sj@kernel.org>]

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.

Signed-off-by: SeongJae Park <sj@kernel.org>
---
 mm/damon/lru_sort.c | 30 +++++++++++++++++++++++++++---
 1 file changed, 27 insertions(+), 3 deletions(-)

diff --git a/mm/damon/lru_sort.c b/mm/damon/lru_sort.c
index f3a9dfc246b6..717cc585d207 100644
--- a/mm/damon/lru_sort.c
+++ b/mm/damon/lru_sort.c
@@ -55,6 +55,20 @@ module_param(commit_inputs, bool, 0600);
 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.
  *
@@ -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);
-- 
2.47.3