mm/damon/reclaim: add autotune_monitoring_intervals parameter

Patch series "mm/damon/reclaim: support monitoring intervals auto-tuning".

The monitoring intervals auto-tuning feature of DAMON has proven to be
useful in multiple environments.  Add a new DAMON_RECLAIM parameter for
supporting the feature, and update the document for the new parameter.

This patch (of 2):

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.

Note that use of the auto-tuning overrides the manually entered monitoring
intervals.  Also, note that the 'min_age' will dynamically changed
proportional to auto-tuned intervals.  It is recommended to use 'min_age'
short enough and use 'quota_mem_pressure_us' like coldness threshold
auto-tuning features together.

Link: https://lore.kernel.org/20260501011740.81988-1-sj@kernel.org
Link: https://lore.kernel.org/20260501011740.81988-2-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: David Hildenbrand <david@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Liam R. Howlett <liam@infradead.org>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/damon/reclaim.c b/mm/damon/reclaim.c
index a60ee800d63e91a13f350032b3bc44db394a7b61..7126d47fb8b2fa8730678d8b11e273c55501e84e 100644 (file)
--- 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 */
@@ -152,7 +166,7 @@ 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 */
@@ -162,8 +176,7 @@ 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,
        };
 
@@ -184,6 +197,7 @@ 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;
@@ -201,12 +215,21 @@ 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);