mm/damon/reclaim: support online inputs update

DAMON_RECLAIM reads the user input parameters only when it starts.  To
allow more efficient online tuning, this commit implements a new input
parameter called 'commit_inputs'.  Writing true to the parameter makes
DAMON_RECLAIM reads the input parameters again.

Link: https://lkml.kernel.org/r/20220429160606.127307-14-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/damon/reclaim.c b/mm/damon/reclaim.c
index 75cfd96..f37c5d4 100644 (file)
--- a/mm/damon/reclaim.c
+++ b/mm/damon/reclaim.c
@@ -30,6 +30,18 @@
 static bool enabled __read_mostly;
 
 /*
+ * Make DAMON_RECLAIM reads the input parameters again, except ``enabled``.
+ *
+ * Input parameters that updated while DAMON_RECLAIM is running are not applied
+ * by default.  Once this parameter is set as ``Y``, DAMON_RECLAIM reads values
+ * of parametrs except ``enabled`` again.  Once the re-reading is done, this
+ * parameter is set as ``N``.  If invalid parameters are found while the
+ * re-reading, DAMON_RECLAIM will be disabled.
+ */
+static bool commit_inputs __read_mostly;
+module_param(commit_inputs, bool, 0600);
+
+/*
  * Time threshold for cold memory regions identification in microseconds.
  *
  * If a memory region is not accessed for this or longer time, DAMON_RECLAIM
@@ -289,57 +301,56 @@ static struct damos *damon_reclaim_new_scheme(void)
        return scheme;
 }
 
-static int damon_reclaim_turn(bool on)
+static int damon_reclaim_apply_parameters(void)
 {
-       struct damon_region *region;
        struct damos *scheme;
-       int err;
-
-       if (!on) {
-               err = damon_stop(&ctx, 1);
-               if (!err)
-                       kdamond_pid = -1;
-               return err;
-       }
+       struct damon_addr_range addr_range;
+       int err = 0;
 
        err = damon_set_attrs(ctx, sample_interval, aggr_interval, 0,
                        min_nr_regions, max_nr_regions);
        if (err)
                return err;
 
+       /* Will be freed by next 'damon_set_schemes()' below */
+       scheme = damon_reclaim_new_scheme();
+       if (!scheme)
+               return -ENOMEM;
+       err = damon_set_schemes(ctx, &scheme, 1);
+       if (err)
+               return err;
+
        if (monitor_region_start > monitor_region_end)
                return -EINVAL;
        if (!monitor_region_start && !monitor_region_end &&
                        !get_monitoring_region(&monitor_region_start,
                                &monitor_region_end))
                return -EINVAL;
-       /* DAMON will free this on its own when finish monitoring */
-       region = damon_new_region(monitor_region_start, monitor_region_end);
-       if (!region)
-               return -ENOMEM;
-       damon_add_region(region, target);
+       addr_range.start = monitor_region_start;
+       addr_range.end = monitor_region_end;
+       return damon_set_regions(target, &addr_range, 1);
+}
 
-       /* Will be freed by 'damon_set_schemes()' below */
-       scheme = damon_reclaim_new_scheme();
-       if (!scheme) {
-               err = -ENOMEM;
-               goto free_region_out;
+static int damon_reclaim_turn(bool on)
+{
+       int err;
+
+       if (!on) {
+               err = damon_stop(&ctx, 1);
+               if (!err)
+                       kdamond_pid = -1;
+               return err;
        }
-       err = damon_set_schemes(ctx, &scheme, 1);
+
+       err = damon_reclaim_apply_parameters();
        if (err)
-               goto free_scheme_out;
+               return err;
 
        err = damon_start(&ctx, 1, true);
-       if (!err) {
-               kdamond_pid = ctx->kdamond->pid;
-               return 0;
-       }
-
-free_scheme_out:
-       damon_destroy_scheme(scheme);
-free_region_out:
-       damon_destroy_region(region, target);
-       return err;
+       if (err)
+               return err;
+       kdamond_pid = ctx->kdamond->pid;
+       return 0;
 }
 
 #define ENABLE_CHECK_INTERVAL_MS       1000
@@ -389,6 +400,7 @@ MODULE_PARM_DESC(enabled,
 static int damon_reclaim_after_aggregation(struct damon_ctx *c)
 {
        struct damos *s;
+       int err = 0;
 
        /* update the stats parameter */
        damon_for_each_scheme(s, c) {
@@ -398,7 +410,23 @@ static int damon_reclaim_after_aggregation(struct damon_ctx *c)
                bytes_reclaimed_regions = s->stat.sz_applied;
                nr_quota_exceeds = s->stat.qt_exceeds;
        }
-       return 0;
+
+       if (commit_inputs) {
+               err = damon_reclaim_apply_parameters();
+               commit_inputs = false;
+       }
+       return err;
+}
+
+static int damon_reclaim_after_wmarks_check(struct damon_ctx *c)
+{
+       int err = 0;
+
+       if (commit_inputs) {
+               err = damon_reclaim_apply_parameters();
+               commit_inputs = false;
+       }
+       return err;
 }
 
 static int __init damon_reclaim_init(void)
@@ -410,6 +438,7 @@ static int __init damon_reclaim_init(void)
        if (damon_select_ops(ctx, DAMON_OPS_PADDR))
                return -EINVAL;
 
+       ctx->callback.after_wmarks_check = damon_reclaim_after_wmarks_check;
        ctx->callback.after_aggregation = damon_reclaim_after_aggregation;
 
        target = damon_new_target();