[RFC PATCH 5/8] mm/damon/sysfs: implement a command to update auto-tuned monitoring intervals

[SeongJae Park <sj@kernel.org>]

DAMON kernel API callers can show auto-tuned sampling and aggregation
intervals from the monmitoring attributes data structure.  That can be
useful for debugging or tuning of the feature.  DAMON user-space ABI
users has no way to see that, though.  Implement a new DAMON sysfs
interface kdamond state command, namely 'update_tuned_intervals', for
the purpose.  Once the command is written to the kdamond state file, the
tuned sampling and aggregation intervals will be updated to the
corresponding sysfs interface.

Signed-off-by: SeongJae Park <sj@kernel.org>
---
 mm/damon/sysfs.c | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/mm/damon/sysfs.c b/mm/damon/sysfs.c
index f9bfe9ea0ae6..b1829ee67762 100644
--- a/mm/damon/sysfs.c
+++ b/mm/damon/sysfs.c
@@ -1213,6 +1213,11 @@ enum damon_sysfs_cmd {
 	 * effective size quota of the scheme in bytes.
 	 */
 	DAMON_SYSFS_CMD_UPDATE_SCHEMES_EFFECTIVE_QUOTAS,
+	/*
+	 * @DAMON_SYSFS_CMD_UPDATE_TUNED_INTERVALS: Update the tuned monitoring
+	 * intevals.
+	 */
+	DAMON_SYSFS_CMD_UPDATE_TUNED_INTERVALS,
 	/*
 	 * @NR_DAMON_SYSFS_CMDS: Total number of DAMON sysfs commands.
 	 */
@@ -1230,6 +1235,7 @@ static const char * const damon_sysfs_cmd_strs[] = {
 	"update_schemes_tried_regions",
 	"clear_schemes_tried_regions",
 	"update_schemes_effective_quotas",
+	"update_tuned_intervals",
 };
 
 /*
@@ -1502,6 +1508,17 @@ static int damon_sysfs_upd_schemes_effective_quotas(void *data)
 	return 0;
 }
 
+static int damon_sysfs_upd_tuned_intervals(void *data)
+{
+	struct damon_sysfs_kdamond *kdamond = data;
+	struct damon_ctx *ctx = kdamond->damon_ctx;
+
+	kdamond->contexts->contexts_arr[0]->attrs->intervals->sample_us =
+		ctx->attrs.sample_interval;
+	kdamond->contexts->contexts_arr[0]->attrs->intervals->aggr_us =
+		ctx->attrs.aggr_interval;
+	return 0;
+}
 
 /*
  * damon_sysfs_cmd_request_callback() - DAMON callback for handling requests.
@@ -1723,6 +1740,9 @@ static int damon_sysfs_handle_cmd(enum damon_sysfs_cmd cmd,
 		return damon_sysfs_damon_call(
 				damon_sysfs_upd_schemes_effective_quotas,
 				kdamond);
+	case DAMON_SYSFS_CMD_UPDATE_TUNED_INTERVALS:
+		return damon_sysfs_damon_call(
+				damon_sysfs_upd_tuned_intervals, kdamond);
 	default:
 		break;
 	}
-- 
2.39.5