linux-kernel - [PATCH 8/8] Docs/admin-guide/mm/damon/stat: document negative idle time

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Message-ID: <20251026182216.118200-9-sj@kernel.org>
Date: Sun, 26 Oct 2025 11:22:13 -0700
From: SeongJae Park <sj@...nel.org>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: SeongJae Park <sj@...nel.org>,
	"Liam R. Howlett" <Liam.Howlett@...cle.com>,
	David Hildenbrand <david@...hat.com>,
	Jonathan Corbet <corbet@....net>,
	Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
	Michal Hocko <mhocko@...e.com>,
	Mike Rapoport <rppt@...nel.org>,
	Suren Baghdasaryan <surenb@...gle.com>,
	Vlastimil Babka <vbabka@...e.cz>,
	damon@...ts.linux.dev,
	linux-doc@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linux-mm@...ck.org
Subject: [PATCH 8/8] Docs/admin-guide/mm/damon/stat: document negative idle time

Commit a983a26d5298 ("mm/damon/stat: expose negative idle time")
introduced the negative idle time feature for DAMON_STAT.  But it is not
documented.  Document it on the usage document.

Signed-off-by: SeongJae Park <sj@...nel.org>
---
 Documentation/admin-guide/mm/damon/stat.rst | 15 ++++++++-------
 1 file changed, 8 insertions(+), 7 deletions(-)

diff --git a/Documentation/admin-guide/mm/damon/stat.rst b/Documentation/admin-guide/mm/damon/stat.rst
index 754f98d47617..e5a5a2c4f803 100644
--- a/Documentation/admin-guide/mm/damon/stat.rst
+++ b/Documentation/admin-guide/mm/damon/stat.rst
@@ -74,12 +74,13 @@ memory_idle_ms_percentiles
 Per-byte idle time (milliseconds) percentiles of the system.
 
 DAMON_STAT calculates how long each byte of the memory was not accessed until
-now (idle time), based on the current DAMON results snapshot.  If DAMON found a
-region of access frequency (nr_accesses) larger than zero, every byte of the
-region gets zero idle time.  If a region has zero access frequency
-(nr_accesses), how long the region was keeping the zero access frequency (age)
-becomes the idle time of every byte of the region.  Then, DAMON_STAT exposes
-the percentiles of the idle time values via this read-only parameter.  Reading
-the parameter returns 101 idle time values in milliseconds, separated by comma.
+now (idle time), based on the current DAMON results snapshot.  For regions
+having access frequency (nr_accesses) larger than zero, how long the current
+access frequency level was kept multiplied by ``-1`` becomes the idlee time of
+every byte of the region.  If a region has zero access frequency (nr_accesses),
+how long the region was keeping the zero access frequency (age) becomes the
+idle time of every byte of the region.  Then, DAMON_STAT exposes the
+percentiles of the idle time values via this read-only parameter.  Reading the
+parameter returns 101 idle time values in milliseconds, separated by comma.
 Each value represents 0-th, 1st, 2nd, 3rd, ..., 99th and 100th percentile idle
 times.
-- 
2.47.3