[RFC PATCH 1/2] mm/damon/reclaim: add autotune_monitoring_intervals parameter

[SeongJae Park <sj@kernel.org>]

DAMON's monitoring intervals auto-tuning feature has proven to be useful
in multiple environments.  DAMON_RECLAIM is still asking users to do the
manual tuning of the intervals.  Add a module parameter for utilizing
the auto-tuning feature with the suggested default setup.

Signed-off-by: SeongJae Park <sj@kernel.org>
---
 mm/damon/reclaim.c | 33 ++++++++++++++++++++++++++++-----
 1 file changed, 28 insertions(+), 5 deletions(-)

diff --git a/mm/damon/reclaim.c b/mm/damon/reclaim.c
index 4fc4a54b5e546..89998d28628c4 100644
--- a/mm/damon/reclaim.c
+++ b/mm/damon/reclaim.c
@@ -91,6 +91,20 @@ module_param(quota_mem_pressure_us, ulong, 0600);
 static unsigned long quota_autotune_feedback __read_mostly;
 module_param(quota_autotune_feedback, ulong, 0600);
 
+/*
+ * Auto-tune monitoring intervals.
+ *
+ * If this parameter is set as ``Y``, DAMON_RECLAIM 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 intervals 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);
+
 static struct damos_watermarks damon_reclaim_wmarks = {
 	.metric = DAMOS_WMARK_FREE_MEM_RATE,
 	.interval = 5000000,	/* 5 seconds */
@@ -159,7 +173,7 @@ DEFINE_DAMON_MODULES_DAMOS_STATS_PARAMS(damon_reclaim_stat,
 static struct damon_ctx *ctx;
 static struct damon_target *target;
 
-static struct damos *damon_reclaim_new_scheme(void)
+static struct damos *damon_reclaim_new_scheme(unsigned long aggr_interval)
 {
 	struct damos_access_pattern pattern = {
 		/* Find regions having PAGE_SIZE or larger size */
@@ -169,8 +183,7 @@ static struct damos *damon_reclaim_new_scheme(void)
 		.min_nr_accesses = 0,
 		.max_nr_accesses = 0,
 		/* for min_age or more micro-seconds */
-		.min_age_region = min_age /
-			damon_reclaim_mon_attrs.aggr_interval,
+		.min_age_region = min_age / aggr_interval,
 		.max_age_region = UINT_MAX,
 	};
 
@@ -191,6 +204,7 @@ static int damon_reclaim_apply_parameters(void)
 {
 	struct damon_ctx *param_ctx;
 	struct damon_target *param_target;
+	struct damon_attrs attrs;
 	struct damos *scheme;
 	struct damos_quota_goal *goal;
 	struct damos_filter *filter;
@@ -208,12 +222,21 @@ static int damon_reclaim_apply_parameters(void)
 		goto out;
 	}
 
-	err = damon_set_attrs(param_ctx, &damon_reclaim_mon_attrs);
+	attrs = damon_reclaim_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;
-	scheme = damon_reclaim_new_scheme();
+	scheme = damon_reclaim_new_scheme(attrs.aggr_interval);
 	if (!scheme)
 		goto out;
 	damon_set_schemes(param_ctx, &scheme, 1);
-- 
2.47.3