* + mm-khugepaged-skip-collapsing-mthp-to-smaller-orders.patch added to mm-new branch
@ 2026-04-23 20:30 Andrew Morton
0 siblings, 0 replies; 3+ messages in thread
From: Andrew Morton @ 2026-04-23 20:30 UTC (permalink / raw)
To: mm-commits, npache, akpm
[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #1: Type: text/plain, Size: 5805 bytes --]
The patch titled
Subject: mm/khugepaged: skip collapsing mTHP to smaller orders
has been added to the -mm mm-new branch. Its filename is
mm-khugepaged-skip-collapsing-mthp-to-smaller-orders.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-khugepaged-skip-collapsing-mthp-to-smaller-orders.patch
This patch will later appear in the mm-new branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
Note, mm-new is a provisional staging ground for work-in-progress
patches, and acceptance into mm-new is a notification for others take
notice and to finish up reviews. Please do not hesitate to respond to
review feedback and post updated versions to replace or incrementally
fixup patches in mm-new.
The mm-new branch of mm.git is not included in linux-next
If a few days of testing in mm-new is successful, the patch will me moved
into mm.git's mm-unstable branch, which is included in linux-next
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next via various
branches at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
and is updated there most days
------------------------------------------------------
From: Nico Pache <npache@redhat.com>
Subject: mm/khugepaged: skip collapsing mTHP to smaller orders
Date: Sun, 19 Apr 2026 12:57:43 -0600
khugepaged may try to collapse a mTHP to a smaller mTHP, resulting in some
pages being unmapped. Skip these cases until we have a way to check if
its ok to collapse to a smaller mTHP size (like in the case of a partially
mapped folio). This check is also not done during the scan phase as the
current collapse order is unknown at that time.
This patch is inspired by Dev Jain's work on khugepaged mTHP support [1].
Link: https://lore.kernel.org/20260419185750.260784-7-npache@redhat.com
Link: https://lore.kernel.org/lkml/20241216165105.56185-11-dev.jain@arm.com/ [1]
Co-developed-by: Dev Jain <dev.jain@arm.com>
Signed-off-by: Dev Jain <dev.jain@arm.com>
Signed-off-by: Nico Pache <npache@redhat.com>
Reviewed-by: Lorenzo Stoakes <ljs@kernel.org>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Acked-by: Usama Arif <usama.arif@linux.dev>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Bagas Sanjaya <bagasdotme@gmail.com>
Cc: Barry Song <baohua@kernel.org>
Cc: Brendan Jackman <jackmanb@google.com>
Cc: Byungchul Park <byungchul@sk.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: David Hildenbrand (Arm) <david@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Gregory Price <gourry@gourry.net>
Cc: "Huang, Ying" <ying.huang@linux.alibaba.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Jann Horn <jannh@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Joshua Hahn <joshua.hahnjy@gmail.com>
Cc: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: Lance Yang <lance.yang@linux.dev>
Cc: Liam Howlett <liam@infradead.org>
Cc: "Masami Hiramatsu (Google)" <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Matthew Brost <matthew.brost@intel.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Nanyong Sun <sunnanyong@huawei.com>
Cc: Pedro Falcato <pfalcato@suse.de>
Cc: Peter Xu <peterx@redhat.com>
Cc: Rafael Aquini <raquini@redhat.com>
Cc: Rakie Kim <rakie.kim@sk.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Shivank Garg <shivankg@amd.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Takashi Iwai (SUSE) <tiwai@suse.de>
Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Cc: Vishal Moola (Oracle) <vishal.moola@gmail.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Wei Yang <richard.weiyang@gmail.com>
Cc: Will Deacon <will@kernel.org>
Cc: Yang Shi <yang@os.amperecomputing.com>
Cc: Zach O'Keefe <zokeefe@google.com>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---
mm/khugepaged.c | 8 ++++++++
1 file changed, 8 insertions(+)
--- a/mm/khugepaged.c~mm-khugepaged-skip-collapsing-mthp-to-smaller-orders
+++ a/mm/khugepaged.c
@@ -686,6 +686,14 @@ static enum scan_result __collapse_huge_
goto out;
}
}
+ /*
+ * TODO: In some cases of partially-mapped folios, we'd actually
+ * want to collapse.
+ */
+ if (!is_pmd_order(order) && folio_order(folio) >= order) {
+ result = SCAN_PTE_MAPPED_HUGEPAGE;
+ goto out;
+ }
if (folio_test_large(folio)) {
struct folio *f;
_
Patches currently in -mm which might be from npache@redhat.com are
mm-khugepaged-generalize-hugepage_vma_revalidate-for-mthp-support.patch
mm-khugepaged-rework-max_ptes_-handling-with-helper-functions.patch
mm-khugepaged-generalize-__collapse_huge_page_-for-mthp-support.patch
mm-khugepaged-generalize-collapse_huge_page-for-mthp-collapse.patch
mm-khugepaged-skip-collapsing-mthp-to-smaller-orders.patch
mm-khugepaged-add-per-order-mthp-collapse-failure-statistics.patch
mm-khugepaged-improve-tracepoints-for-mthp-orders.patch
mm-khugepaged-introduce-collapse_allowable_orders-helper-function.patch
mm-khugepaged-introduce-mthp-collapse-support.patch
mm-khugepaged-avoid-unnecessary-mthp-collapse-attempts.patch
documentation-mm-update-the-admin-guide-for-mthp-collapse.patch
^ permalink raw reply [flat|nested] 3+ messages in thread* + mm-khugepaged-skip-collapsing-mthp-to-smaller-orders.patch added to mm-new branch
@ 2026-05-03 13:30 Andrew Morton
0 siblings, 0 replies; 3+ messages in thread
From: Andrew Morton @ 2026-05-03 13:30 UTC (permalink / raw)
To: mm-commits, zokeefe, ziy, ying.huang, yang, willy, will,
wangkefeng.wang, vishal.moola, vbabka, usama.arif, tiwai,
thomas.hellstrom, surenb, sunnanyong, shivankg, ryan.roberts,
rppt, rostedt, rientjes, richard.weiyang, rdunlap, raquini,
rakie.kim, pfalcato, peterx, mhocko, mhiramat, matthew.brost,
mathieu.desnoyers, ljs, liam, lance.yang, joshua.hahnjy, jannh,
jack, jackmanb, hughd, hannes, gourry, dev.jain, david, corbet,
catalin.marinas, byungchul, baolin.wang, baohua, bagasdotme,
apopple, anshuman.khandual, aarcange, npache, akpm
[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
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The patch titled
Subject: mm/khugepaged: skip collapsing mTHP to smaller orders
has been added to the -mm mm-new branch. Its filename is
mm-khugepaged-skip-collapsing-mthp-to-smaller-orders.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-khugepaged-skip-collapsing-mthp-to-smaller-orders.patch
This patch will later appear in the mm-new branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
Note, mm-new is a provisional staging ground for work-in-progress
patches, and acceptance into mm-new is a notification for others take
notice and to finish up reviews. Please do not hesitate to respond to
review feedback and post updated versions to replace or incrementally
fixup patches in mm-new.
The mm-new branch of mm.git is not included in linux-next
If a few days of testing in mm-new is successful, the patch will me moved
into mm.git's mm-unstable branch, which is included in linux-next
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next via various
branches at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
and is updated there most days
------------------------------------------------------
From: Nico Pache <npache@redhat.com>
Subject: mm/khugepaged: skip collapsing mTHP to smaller orders
Date: Sun, 19 Apr 2026 12:57:43 -0600
khugepaged may try to collapse a mTHP to a smaller mTHP, resulting in some
pages being unmapped. Skip these cases until we have a way to check if
its ok to collapse to a smaller mTHP size (like in the case of a partially
mapped folio). This check is also not done during the scan phase as the
current collapse order is unknown at that time.
This patch is inspired by Dev Jain's work on khugepaged mTHP support [1].
Link: https://lore.kernel.org/20260419185750.260784-7-npache@redhat.com
Link: https://lore.kernel.org/lkml/20241216165105.56185-11-dev.jain@arm.com/ [1]
Co-developed-by: Dev Jain <dev.jain@arm.com>
Signed-off-by: Dev Jain <dev.jain@arm.com>
Signed-off-by: Nico Pache <npache@redhat.com>
Reviewed-by: Lorenzo Stoakes <ljs@kernel.org>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Acked-by: Usama Arif <usama.arif@linux.dev>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Bagas Sanjaya <bagasdotme@gmail.com>
Cc: Barry Song <baohua@kernel.org>
Cc: Brendan Jackman <jackmanb@google.com>
Cc: Byungchul Park <byungchul@sk.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: David Hildenbrand (Arm) <david@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Gregory Price <gourry@gourry.net>
Cc: "Huang, Ying" <ying.huang@linux.alibaba.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Jann Horn <jannh@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Joshua Hahn <joshua.hahnjy@gmail.com>
Cc: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: Lance Yang <lance.yang@linux.dev>
Cc: Liam Howlett <liam@infradead.org>
Cc: "Masami Hiramatsu (Google)" <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Matthew Brost <matthew.brost@intel.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Nanyong Sun <sunnanyong@huawei.com>
Cc: Pedro Falcato <pfalcato@suse.de>
Cc: Peter Xu <peterx@redhat.com>
Cc: Rafael Aquini <raquini@redhat.com>
Cc: Rakie Kim <rakie.kim@sk.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Shivank Garg <shivankg@amd.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Takashi Iwai (SUSE) <tiwai@suse.de>
Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Cc: Vishal Moola (Oracle) <vishal.moola@gmail.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Wei Yang <richard.weiyang@gmail.com>
Cc: Will Deacon <will@kernel.org>
Cc: Yang Shi <yang@os.amperecomputing.com>
Cc: Zach O'Keefe <zokeefe@google.com>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---
mm/khugepaged.c | 8 ++++++++
1 file changed, 8 insertions(+)
--- a/mm/khugepaged.c~mm-khugepaged-skip-collapsing-mthp-to-smaller-orders
+++ a/mm/khugepaged.c
@@ -686,6 +686,14 @@ static enum scan_result __collapse_huge_
goto out;
}
}
+ /*
+ * TODO: In some cases of partially-mapped folios, we'd actually
+ * want to collapse.
+ */
+ if (!is_pmd_order(order) && folio_order(folio) >= order) {
+ result = SCAN_PTE_MAPPED_HUGEPAGE;
+ goto out;
+ }
if (folio_test_large(folio)) {
struct folio *f;
_
Patches currently in -mm which might be from npache@redhat.com are
mm-khugepaged-generalize-hugepage_vma_revalidate-for-mthp-support.patch
mm-khugepaged-rework-max_ptes_-handling-with-helper-functions.patch
mm-khugepaged-generalize-__collapse_huge_page_-for-mthp-support.patch
mm-khugepaged-generalize-collapse_huge_page-for-mthp-collapse.patch
mm-khugepaged-skip-collapsing-mthp-to-smaller-orders.patch
mm-khugepaged-add-per-order-mthp-collapse-failure-statistics.patch
mm-khugepaged-improve-tracepoints-for-mthp-orders.patch
mm-khugepaged-introduce-collapse_allowable_orders-helper-function.patch
mm-khugepaged-introduce-mthp-collapse-support.patch
mm-khugepaged-avoid-unnecessary-mthp-collapse-attempts.patch
documentation-mm-update-the-admin-guide-for-mthp-collapse.patch
^ permalink raw reply [flat|nested] 3+ messages in thread* + mm-khugepaged-skip-collapsing-mthp-to-smaller-orders.patch added to mm-new branch
@ 2026-05-11 21:05 Andrew Morton
0 siblings, 0 replies; 3+ messages in thread
From: Andrew Morton @ 2026-05-11 21:05 UTC (permalink / raw)
To: mm-commits, npache, akpm
[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #1: Type: text/plain, Size: 5931 bytes --]
The patch titled
Subject: mm/khugepaged: skip collapsing mTHP to smaller orders
has been added to the -mm mm-new branch. Its filename is
mm-khugepaged-skip-collapsing-mthp-to-smaller-orders.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-khugepaged-skip-collapsing-mthp-to-smaller-orders.patch
This patch will later appear in the mm-new branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
Note, mm-new is a provisional staging ground for work-in-progress
patches, and acceptance into mm-new is a notification for others take
notice and to finish up reviews. Please do not hesitate to respond to
review feedback and post updated versions to replace or incrementally
fixup patches in mm-new.
The mm-new branch of mm.git is not included in linux-next
If a few days of testing in mm-new is successful, the patch will me moved
into mm.git's mm-unstable branch, which is included in linux-next
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next via various
branches at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
and is updated there most days
------------------------------------------------------
From: Nico Pache <npache@redhat.com>
Subject: mm/khugepaged: skip collapsing mTHP to smaller orders
Date: Mon, 11 May 2026 12:58:07 -0600
khugepaged may try to collapse a mTHP to a smaller mTHP, resulting in some
pages being unmapped. Skip these cases until we have a way to check if
its ok to collapse to a smaller mTHP size (like in the case of a partially
mapped folio). This check is also not done during the scan phase as the
current collapse order is unknown at that time.
This patch is inspired by Dev Jain's work on khugepaged mTHP support [1].
Link: https://lore.kernel.org/20260511185817.686831-8-npache@redhat.com
Link: https://lore.kernel.org/lkml/20241216165105.56185-11-dev.jain@arm.com/ [1]
Co-developed-by: Dev Jain <dev.jain@arm.com>
Signed-off-by: Dev Jain <dev.jain@arm.com>
Signed-off-by: Nico Pache <npache@redhat.com>
Reviewed-by: Lorenzo Stoakes <ljs@kernel.org>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Acked-by: Usama Arif <usama.arif@linux.dev>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Bagas Sanjaya <bagasdotme@gmail.com>
Cc: Barry Song <baohua@kernel.org>
Cc: Brendan Jackman <jackmanb@google.com>
Cc: Byungchul Park <byungchul@sk.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: David Hildenbrand (Arm) <david@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Gregory Price <gourry@gourry.net>
Cc: "Huang, Ying" <ying.huang@linux.alibaba.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Jann Horn <jannh@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Joshua Hahn <joshua.hahnjy@gmail.com>
Cc: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: Lance Yang <lance.yang@linux.dev>
Cc: Liam R. Howlett <liam@infradead.org>
Cc: "Masami Hiramatsu (Google)" <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Matthew Brost <matthew.brost@intel.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Nanyong Sun <sunnanyong@huawei.com>
Cc: Pedro Falcato <pfalcato@suse.de>
Cc: Peter Xu <peterx@redhat.com>
Cc: Rafael Aquini <raquini@redhat.com>
Cc: Rakie Kim <rakie.kim@sk.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Shivank Garg <shivankg@amd.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Takashi Iwai (SUSE) <tiwai@suse.de>
Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Cc: Usama Arif <usamaarif642@gmail.com>
Cc: Vishal Moola (Oracle) <vishal.moola@gmail.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Wei Yang <richard.weiyang@gmail.com>
Cc: Will Deacon <will@kernel.org>
Cc: Yang Shi <yang@os.amperecomputing.com>
Cc: Zach O'Keefe <zokeefe@google.com>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---
mm/khugepaged.c | 8 ++++++++
1 file changed, 8 insertions(+)
--- a/mm/khugepaged.c~mm-khugepaged-skip-collapsing-mthp-to-smaller-orders
+++ a/mm/khugepaged.c
@@ -685,6 +685,14 @@ static enum scan_result __collapse_huge_
goto out;
}
}
+ /*
+ * TODO: In some cases of partially-mapped folios, we'd actually
+ * want to collapse.
+ */
+ if (!is_pmd_order(order) && folio_order(folio) >= order) {
+ result = SCAN_PTE_MAPPED_HUGEPAGE;
+ goto out;
+ }
if (folio_test_large(folio)) {
struct folio *f;
_
Patches currently in -mm which might be from npache@redhat.com are
mm-khugepaged-generalize-hugepage_vma_revalidate-for-mthp-support.patch
mm-khugepaged-rework-max_ptes_-handling-with-helper-functions.patch
mm-khugepaged-generalize-__collapse_huge_page_-for-mthp-support.patch
mm-khugepaged-require-collapse_huge_page-to-enter-exit-with-the-lock-dropped.patch
mm-khugepaged-generalize-collapse_huge_page-for-mthp-collapse.patch
mm-khugepaged-skip-collapsing-mthp-to-smaller-orders.patch
mm-khugepaged-add-per-order-mthp-collapse-failure-statistics.patch
mm-khugepaged-improve-tracepoints-for-mthp-orders.patch
mm-khugepaged-introduce-collapse_allowable_orders-helper-function.patch
mm-khugepaged-introduce-mthp-collapse-support.patch
mm-khugepaged-avoid-unnecessary-mthp-collapse-attempts.patch
documentation-mm-update-the-admin-guide-for-mthp-collapse.patch
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2026-05-11 21:05 UTC | newest]
Thread overview: 3+ messages (download: mbox.gz follow: Atom feed
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2026-04-23 20:30 + mm-khugepaged-skip-collapsing-mthp-to-smaller-orders.patch added to mm-new branch Andrew Morton
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2026-05-03 13:30 Andrew Morton
2026-05-11 21:05 Andrew Morton
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