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

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

[Andrew Morton]

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
review feedback and post updated versions to replace or incrementally
fixup patches in mm-new.

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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