linux.git/Documentation/admin-guide/mm, branch v6.16

Docs/damon: update titles and brief introductions to explain DAMOS

2025-05-22T21:55:38+00:00

DAMON was initially developed only for data access monitoring, and then
extended for not only access monitoring but also access-aware system
operations (DAMOS).  But the documents have old titles and brief
introductions for only the monitoring part.  Update the titles and the
brief introductions to explain DAMOS part together.

Link: https://lkml.kernel.org/r/20250513002715.40126-7-sj@kernel.org
Signed-off-by: SeongJae Park 
Cc: Brendan Higgins 
Cc: David Gow 
Cc: Jonathan Corbet 
Cc: Shuah Khan 
Signed-off-by: Andrew Morton

Documentation: add documentation for KHO

2025-05-13T06:50:42+00:00

With KHO in place, let's add documentation that describes what it is and
how to use it.

Link: https://lkml.kernel.org/r/20250509074635.3187114-17-changyuanl@google.com
Signed-off-by: Alexander Graf 
Co-developed-by: Mike Rapoport (Microsoft) 
Signed-off-by: Mike Rapoport (Microsoft) 
Co-developed-by: Changyuan Lyu 
Signed-off-by: Changyuan Lyu 
Cc: Andy Lutomirski 
Cc: Anthony Yznaga 
Cc: Arnd Bergmann 
Cc: Ashish Kalra 
Cc: Ben Herrenschmidt 
Cc: Borislav Betkov 
Cc: Catalin Marinas 
Cc: Dave Hansen 
Cc: David Woodhouse 
Cc: Eric Biederman 
Cc: "H. Peter Anvin" 
Cc: Ingo Molnar 
Cc: James Gowans 
Cc: Jason Gunthorpe 
Cc: Jonathan Corbet 
Cc: Krzysztof Kozlowski 
Cc: Marc Rutland 
Cc: Paolo Bonzini 
Cc: Pasha Tatashin 
Cc: Peter Zijlstra 
Cc: Pratyush Yadav 
Cc: Rob Herring 
Cc: Saravana Kannan 
Cc: Stanislav Kinsburskii 
Cc: Steven Rostedt 
Cc: Thomas Gleinxer 
Cc: Thomas Lendacky 
Cc: Will Deacon 
Signed-off-by: Andrew Morton

mm: add max swappiness arg to lru_gen for anonymous memory only

2025-05-13T06:50:36+00:00

The MGLRU already supports reclaiming only from anonymous memory via the
/sys/kernel/debug/lru_gen interface.  Now, memory.reclaim also supports
the swappiness=max parameter to enable reclaiming solely from anonymous
memory.  To unify the semantics of proactive reclaiming from anonymous
folios, the max parameter is introduced.

[hezhongkun.hzk@bytedance.com: use strcmp instead of strncmp, if swappiness is not set, use the default value]
  Link: https://lkml.kernel.org/r/20250507071057.3184240-1-hezhongkun.hzk@bytedance.com
[akpm@linux-foundation.org: tweak coding style]
Link: https://lkml.kernel.org/r/65181f7745d657d664d833c26d8a94cae40538b9.1745225696.git.hezhongkun.hzk@bytedance.com
Signed-off-by: Zhongkun He 
Acked-by: Muchun Song 
Cc: Johannes Weiner 
Cc: Michal Hocko 
Cc: Yosry Ahmed 
Cc: Yu Zhao 
Signed-off-by: Andrew Morton

Docs/admin-guide/mm/damon/usage: document 'nid' file

2025-05-13T06:50:30+00:00

Add description of 'nid' file, which is optionally used for specific DAMOS
quota goal metrics such as node_mem_{used,free}_bp on DAMON usage
document.

Link: https://lkml.kernel.org/r/20250420194030.75838-6-sj@kernel.org
Signed-off-by: SeongJae Park 
Cc: Jonathan Corbet 
Cc: Yunjeong Mun 
Signed-off-by: Andrew Morton

fs/proc: extend the PAGEMAP_SCAN ioctl to report guard regions

2025-05-12T00:48:16+00:00

Patch series "fs/proc: extend the PAGEMAP_SCAN ioctl to report guard
regions", v2.

Introduce the PAGE_IS_GUARD flag in the PAGEMAP_SCAN ioctl to expose
information about guard regions.  This allows userspace tools, such as
CRIU, to detect and handle guard regions.

Currently, CRIU utilizes PAGEMAP_SCAN as a more efficient alternative to
parsing /proc/pid/pagemap.  Without this change, guard regions are
incorrectly reported as swap-anon regions, leading CRIU to attempt dumping
them and subsequently failing.

The series includes updates to the documentation and selftests to reflect
the new functionality.


This patch (of 3):

Introduce the PAGE_IS_GUARD flag in the PAGEMAP_SCAN ioctl to expose
information about guard regions.  This allows userspace tools, such as
CRIU, to detect and handle guard regions.

Link: https://lkml.kernel.org/r/20250324065328.107678-1-avagin@google.com
Link: https://lkml.kernel.org/r/20250324065328.107678-2-avagin@google.com
Signed-off-by: Andrei Vagin 
Acked-by: David Hildenbrand 
Reviewed-by: Lorenzo Stoakes 
Cc: Jonathan Corbet 
Cc: Shuah Khan 
Signed-off-by: Andrew Morton

Docs/admin-guide/mm/damon/usage: update for {core,ops}_filters directories

2025-03-18T05:06:50+00:00

Document {core,ops}_filters directories on usage document.

Link: https://lkml.kernel.org/r/20250305222733.59089-9-sj@kernel.org
Signed-off-by: SeongJae Park 
Cc: Jonathan Corbet 
Signed-off-by: Andrew Morton

fs/proc/task_mmu: remove per-page mapcount dependency for PM_MMAP_EXCLUSIVE (CONFIG_NO_PAGE_MAPCOUNT)

2025-03-18T05:06:47+00:00

Let's implement an alternative when per-page mapcounts in large folios are
no longer maintained -- soon with CONFIG_NO_PAGE_MAPCOUNT.

PM_MMAP_EXCLUSIVE will now be set if folio_likely_mapped_shared() is true
-- when the folio is considered "mapped shared", including when it once
was "mapped shared" but no longer is, as documented.

This might result in and under-indication of "exclusively mapped", which
is considered better than over-indicating it: under-estimating the USS
(Unique Set Size) is better than over-estimating it.

As an alternative, we could simply remove that flag with
CONFIG_NO_PAGE_MAPCOUNT completely, but there might be value to it.  So,
let's keep it like that and document the behavior.

Link: https://lkml.kernel.org/r/20250303163014.1128035-18-david@redhat.com
Signed-off-by: David Hildenbrand 
Cc: Andy Lutomirks^H^Hski 
Cc: Borislav Betkov 
Cc: Dave Hansen 
Cc: Ingo Molnar 
Cc: Jann Horn 
Cc: Johannes Weiner 
Cc: Jonathan Corbet 
Cc: Kirill A. Shutemov 
Cc: Lance Yang 
Cc: Liam Howlett 
Cc: Lorenzo Stoakes 
Cc: Matthew Wilcow (Oracle) 
Cc: Michal Koutn 
Cc: Muchun Song 
Cc: tejun heo 
Cc: Thomas Gleixner 
Cc: Vlastimil Babka 
Cc: Zefan Li 
Signed-off-by: Andrew Morton

fs/proc/page: remove per-page mapcount dependency for /proc/kpagecount (CONFIG_NO_PAGE_MAPCOUNT)

2025-03-18T05:06:47+00:00

Let's implement an alternative when per-page mapcounts in large folios are
no longer maintained -- soon with CONFIG_NO_PAGE_MAPCOUNT.

For large folios, we'll return the per-page average mapcount within the
folio, whereby we round to the closest integer when calculating the
average: however, we'll always return at least 1 if the folio is mapped.

So assuming a folio with 512 pages, the average would be:
* 0 if not pages are mapped
* 1 if there are 1 .. 767 per-page mappings
* 2 if there are 767 .. 1279 per-page mappings
...

For hugetlb folios and for large folios that are fully mapped into all
address spaces, there is no change.

We'll make use of this helper in other context next.

As an alternative, we could simply return 0 for non-hugetlb large folios,
or disable this legacy interface with CONFIG_NO_PAGE_MAPCOUNT.

But the information exposed by this interface can still be valuable, and
frequently we deal with fully-mapped large folios where the average
corresponds to the actual page mapcount.  So we'll leave it like this for
now and document the new behavior.

Note: this interface is likely not very relevant for performance.  If ever
required, we could try doing a rather expensive rmap walk to collect
precisely how often this folio page is mapped.

Link: https://lkml.kernel.org/r/20250303163014.1128035-17-david@redhat.com
Signed-off-by: David Hildenbrand 
Cc: Andy Lutomirks^H^Hski 
Cc: Borislav Betkov 
Cc: Dave Hansen 
Cc: Ingo Molnar 
Cc: Jann Horn 
Cc: Johannes Weiner 
Cc: Jonathan Corbet 
Cc: Kirill A. Shutemov 
Cc: Lance Yang 
Cc: Liam Howlett 
Cc: Lorenzo Stoakes 
Cc: Matthew Wilcow (Oracle) 
Cc: Michal Koutn 
Cc: Muchun Song 
Cc: tejun heo 
Cc: Thomas Gleixner 
Cc: Vlastimil Babka 
Cc: Zefan Li 
Signed-off-by: Andrew Morton

mm: hugetlb: add hugetlb_alloc_threads cmdline option

2025-03-17T07:05:36+00:00

Add a command line option that enables control of how many threads should
be used to allocate huge pages.

[akpm@linux-foundation.org: tidy up a comment]
Link: https://lkml.kernel.org/r/20250227-hugepage-parameter-v2-2-7db8c6dc0453@cyberus-technology.de
Signed-off-by: Thomas Prescher 
Cc: Jonathan Corbet 
Cc: Muchun Song 
Signed-off-by: Andrew Morton

Docs/admin-guide/mm/damon/usage: add intervals_goal directory on the hierarchy

2025-03-17T07:05:34+00:00

Document DAMON sysfs interface usage for DAMON sampling and aggregation
intervals auto-tuning.

Link: https://lkml.kernel.org/r/20250303221726.484227-9-sj@kernel.org
Signed-off-by: SeongJae Park 
Cc: Jonathan Corbet 
Signed-off-by: Andrew Morton