+ mm-damon-stat-expose-the-current-tuned-aggregation-interval.patch added to mm-new branch

+ mm-damon-stat-expose-the-current-tuned-aggregation-interval.patch added to mm-new branch

[Andrew Morton]

The patch titled
     Subject: mm/damon/stat: expose the current tuned aggregation interval
has been added to the -mm mm-new branch.  Its filename is
     mm-damon-stat-expose-the-current-tuned-aggregation-interval.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-damon-stat-expose-the-current-tuned-aggregation-interval.patch

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

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patches, and acceptance into mm-new is a notification for others take
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------------------------------------------------------
From: SeongJae Park <sj@kernel.org>
Subject: mm/damon/stat: expose the current tuned aggregation interval
Date: Tue, 16 Sep 2025 11:31:26 -0700

Patch series "mm/damon/stat: expose auto-tuned intervals and non-idle
ages".

DAMON_STAT is intentionally providing limited information for easy
consumption of the information.  From production fleet level usages, below
limitations are found, though.

The aggregation interval of DAMON_STAT represents the granularity of the
memory_idle_ms_percentiles.  But the interval is auto-tuned and not
exposed to users, so users cannot know the granularity.

All memory regions of non-zero (positive) nr_accesses are treated as
having zero idle time.  A significant portion of production systems have
such zero idle time.  Hence breakdown of warm and hot data is nearly
impossible.

Make following changes to overcome the limitations.  Expose the auto-tuned
aggregation interval with a new parameter named aggr_interval_us.  Expose
the age of non-zero nr_accesses (how long >0 access frequency the region
retained) regions as a negative idle time.


This patch (of 2):

DAMON_STAT calculates the idle time for a region as the region's age
multiplied by the aggregation interval.  That is, the aggregation interval
is the granularity of the idle time.  Since the aggregation interval is
auto-tuned and not exposed to users, however, users cannot easily know in
what granularity the stat is made.  Expose the tuned aggregation interval
in microseconds via a new parameter, aggr_interval_us.

Link: https://lkml.kernel.org/r/20250916183127.65708-1-sj@kernel.org
Link: https://lkml.kernel.org/r/20250916183127.65708-2-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/damon/stat.c |    6 ++++++
 1 file changed, 6 insertions(+)

--- a/mm/damon/stat.c~mm-damon-stat-expose-the-current-tuned-aggregation-interval
+++ a/mm/damon/stat.c
@@ -39,6 +39,11 @@ module_param_array(memory_idle_ms_percen
 MODULE_PARM_DESC(memory_idle_ms_percentiles,
 		"Memory idle time percentiles in milliseconds");
 
+static unsigned long aggr_interval_us;
+module_param(aggr_interval_us, ulong, 0400);
+MODULE_PARM_DESC(aggr_interval_us,
+		"Current tuned aggregation interval in microseconds");
+
 static struct damon_ctx *damon_stat_context;
 
 static void damon_stat_set_estimated_memory_bandwidth(struct damon_ctx *c)
@@ -133,6 +138,7 @@ static int damon_stat_damon_call_fn(void
 		return 0;
 	last_refresh_jiffies = jiffies;
 
+	aggr_interval_us = c->attrs.aggr_interval;
 	damon_stat_set_estimated_memory_bandwidth(c);
 	damon_stat_set_idletime_percentiles(c);
 	return 0;
_

Patches currently in -mm which might be from sj@kernel.org are

mm-damon-lru_sort-use-param_ctx-for-damon_attrs-staging.patch
mm-damon-core-reset-age-if-nr_accesses-changes-between-non-zero-and-zero.patch
mm-damon-core-set-effective-quota-on-first-charge-window.patch
docs-mm-damon-maintainer-profile-update-community-meetup-for-reservation-requirements.patch
docs-admin-guide-mm-damon-start-add-target_pid-to-damos-example-command.patch
maintainers-rename-damon-section.patch
mm-damon-core-implement-damon_initialized-function.patch
mm-damon-stat-use-damon_initialized.patch
mm-damon-reclaim-use-damon_initialized.patch
mm-damon-lru_sort-use-damon_initialized.patch
samples-damon-wsse-use-damon_initialized.patch
samples-damon-prcl-use-damon_initialized.patch
samples-damon-mtier-use-damon_initialized.patch
mm-damon-stat-expose-the-current-tuned-aggregation-interval.patch
mm-damon-stat-expose-negative-idle-time.patch