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.

Link: https://lkml.kernel.org/r/20251026182216.118200-9-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/Documentation/admin-guide/mm/damon/stat.rst b/Documentation/admin-guide/mm/damon/stat.rst
index 754f98d47617a462f54744311200611666d625b0..e5a5a2c4f803a0de1164ede260095b783136b909 100644 (file)
--- 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.