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mm/ksm: fix advisor_min_pages_to_scan description

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Both Documentation/admin-guide/mm/ksm.rst and the comment next to the
variable definition in mm/ksm.c describe advisor_min_pages_to_scan as a
lower limit of the pages_to_scan parameter, but that is not how the
scan-time advisor actually uses it.  commit 4e5fa4f5ef ("mm/ksm: add ksm
advisor") only uses it to initialize ksm_thread_pages_to_scan when the
scan-time advisor is enabled.

ksm_thread_pages_to_scan is adjusted by scan_time_advisor() after a full
scan finishes.  ksm_thread_pages_to_scan could be increased or decreased
depend on the real scan time is longer or shorter than the target scan
time.  The min value of ksm_thread_pages_to_scan is only limited by
KSM_ADVISOR_MIN_CPU, so ksm_thread_pages_to_scan could be smaller than
ksm_advisor_min_pages_to_scan.

The semantics of advisor_min_pages_to_scan was updated in the v2 patchset
[1], but the documentation wasn't updated.

Update the documentation and comment to match the semantics of
advisor_min_pages_to_scan.

Link: https://lore.kernel.org/linux-mm/20231028000945.2428830-2-shr@devkernel.io/ [1]
Link: https://lore.kernel.org/20260824061010.3343959-3-tujinjiang@huawei.com
Signed-off-by: Jinjiang Tu <tujinjiang@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: David Hildenbrand (Arm) <david@kernel.org>
Reviewed-by: Lorenzo Stoakes (ARM) <ljs@kernel.org>
Cc: Chengming Zhou <chengming.zhou@linux.dev>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: Liam R. Howlett <liam@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Nanyong Sun <sunnanyong@huawei.com>
Cc: Stefan Roesch <shr@devkernel.io>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Cc: xu xin <xu.xin16@zte.com.cn>
Cc: Randy Dunlap <rdunlap@infradead.org>
This commit is contained in:
Jinjiang Tu 2026-08-24 14:10:10 +08:00 committed by Andrew Morton
parent 172c05ebab
commit 585bb36e6a
2 changed files with 3 additions and 3 deletions
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4
Documentation/admin-guide/mm/ksm.rst
View File

@ -183,8 +183,8 @@ advisor_target_scan_time
pages. The default value is 200 seconds.
advisor_min_pages_to_scan
specifies the lower limit of the ``pages_to_scan`` parameter of the
scan time advisor. The default is 500.
specifies the initial value of the ``pages_to_scan`` parameter of
the scan time advisor. The default is 500.
advisor_max_pages_to_scan
specifies the upper limit of the ``pages_to_scan`` parameter of the

2
mm/ksm.c
View File

@ -348,7 +348,7 @@ static enum ksm_advisor_type ksm_advisor;
* Only called through the sysfs control interface:
*/
/* At least scan this many pages per batch. */
/* Initial number of pages to scan per batch. */
static unsigned long ksm_advisor_min_pages_to_scan = 500;
static void set_advisor_defaults(void)