+ mm-damon-core-skip-needless-update-of-damon_attrs-in-damon_commit_ctx.patch added to mm-new branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: mm/damon/core: skip needless update of damon_attrs in damon_commit_ctx()
has been added to the -mm mm-new branch.  Its filename is
     mm-damon-core-skip-needless-update-of-damon_attrs-in-damon_commit_ctx.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-damon-core-skip-needless-update-of-damon_attrs-in-damon_commit_ctx.patch

This patch will later appear in the mm-new branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

Note, mm-new is a provisional staging ground for work-in-progress
patches, and acceptance into mm-new is a notification for others take
notice and to finish up reviews.  Please do not hesitate to respond to
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------------------------------------------------------
From: Bijan Tabatabai <bijantabatab@micron.com>
Subject: mm/damon/core: skip needless update of damon_attrs in damon_commit_ctx()
Date: Wed, 6 Aug 2025 18:42:54 -0500

Currently, damon_commit_ctx() always calls damon_set_attrs() even if the
attributes have not been changed.  This can be problematic when the DAMON
state is committed relatively frequently because damon_set_attrs() resets
ctx->next_{aggregation,ops_update}_sis, causing aggregation and ops update
operations to be needlessly delayed.

This patch avoids this by only calling damon_set_attrs() in
damon_commit_ctx when the attributes have been changed.

Link: https://lkml.kernel.org/r/20250806234254.10572-1-bijan311@gmail.com
Signed-off-by: Bijan Tabatabai <bijantabatab@micron.com>
Reviewed-by: SeongJae Park <sj@kernel.org>
Cc: Bijan Tabatabai <bijan311@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/damon/core.c |   26 +++++++++++++++++++++++---
 1 file changed, 23 insertions(+), 3 deletions(-)

--- a/mm/damon/core.c~mm-damon-core-skip-needless-update-of-damon_attrs-in-damon_commit_ctx
+++ a/mm/damon/core.c
@@ -570,6 +570,24 @@ void damon_destroy_ctx(struct damon_ctx
 	kfree(ctx);
 }
 
+static bool damon_attrs_equals(const struct damon_attrs *attrs1,
+		const struct damon_attrs *attrs2)
+{
+	const struct damon_intervals_goal *ig1 = &attrs1->intervals_goal;
+	const struct damon_intervals_goal *ig2 = &attrs2->intervals_goal;
+
+	return attrs1->sample_interval == attrs2->sample_interval &&
+		attrs1->aggr_interval == attrs2->aggr_interval &&
+		attrs1->ops_update_interval == attrs2->ops_update_interval &&
+		attrs1->min_nr_regions == attrs2->min_nr_regions &&
+		attrs1->max_nr_regions == attrs2->max_nr_regions &&
+		ig1->access_bp == ig2->access_bp &&
+		ig1->aggrs == ig2->aggrs &&
+		ig1->min_sample_us == ig2->min_sample_us &&
+		ig1->max_sample_us == ig2->max_sample_us;
+
+}
+
 static unsigned int damon_age_for_new_attrs(unsigned int age,
 		struct damon_attrs *old_attrs, struct damon_attrs *new_attrs)
 {
@@ -1209,9 +1227,11 @@ int damon_commit_ctx(struct damon_ctx *d
 	 * 2. ops update should be done after pid handling is done (target
 	 *    committing require putting pids).
 	 */
-	err = damon_set_attrs(dst, &src->attrs);
-	if (err)
-		return err;
+	if (!damon_attrs_equals(&dst->attrs, &src->attrs)) {
+		err = damon_set_attrs(dst, &src->attrs);
+		if (err)
+			return err;
+	}
 	dst->ops = src->ops;
 
 	return 0;
_

Patches currently in -mm which might be from bijantabatab@micron.com are

mm-damon-core-skip-needless-update-of-damon_attrs-in-damon_commit_ctx.patch