* + mm-collapse-work-out-the-orders-a-vma-allows-once-per-vma.patch added to mm-unstable branch
@ 2026-09-28 22:01 Andrew Morton
0 siblings, 0 replies; 2+ messages in thread
From: Andrew Morton @ 2026-09-28 22:01 UTC (permalink / raw)
To: mm-commits, kas, akpm
The patch titled
Subject: mm/collapse: work out the orders a VMA allows once per VMA
has been added to the -mm mm-unstable branch. Its filename is
mm-collapse-work-out-the-orders-a-vma-allows-once-per-vma.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-collapse-work-out-the-orders-a-vma-allows-once-per-vma.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
Before you just go and hit "reply", please:
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*** 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: "Kiryl Shutsemau (Meta)" <kas@kernel.org>
Subject: mm/collapse: work out the orders a VMA allows once per VMA
Date: Mon, 28 Sep 2026 11:06:25 +0100
The scan asked collapse_possible_orders() for every PTE table, for an
answer that is a property of the VMA. Both callers walk a VMA a table at
a time, so let them work it out once and pass the mask in. It is only
good while the lock that produced it is held, so madvise_collapse() takes
it again after every collapse.
The mask is then sampled once per VMA rather than once per table. A thp
enabled knob written during a walk takes effect one VMA later, and cannot
widen a collapse: hugepage_vma_revalidate() tests the order again under
the lock the collapse retakes.
Link: https://lore.kernel.org/20260928100630.21870-12-kirill@shutemov.name
Signed-off-by: Kiryl Shutsemau (Meta) <kas@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Zi Yan <ziy@nvidia.com>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Assisted-by: LLM
Cc: David Hildenbrand <david@kernel.org>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Liam R. Howlett <liam@infradead.org>
Cc: Nico Pache <nico.pache@linux.dev>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Dev Jain <dev.jain@arm.com>
Cc: Barry Song <baohua@kernel.org>
Cc: Lance Yang <lance.yang@linux.dev>
Cc: Usama Arif <usama.arif@linux.dev>
Cc: Vlastimil Babka <vbabka@kernel.org>
Cc: Jann Horn <jannh@google.com>
---
mm/khugepaged.c | 32 ++++++++++++++++++--------------
1 file changed, 18 insertions(+), 14 deletions(-)
--- a/mm/khugepaged.c~mm-collapse-work-out-the-orders-a-vma-allows-once-per-vma
+++ a/mm/khugepaged.c
@@ -1577,12 +1577,12 @@ done:
}
static enum scan_result collapse_scan_anon_pmd(struct vm_area_struct *vma,
- unsigned long start_addr, struct collapse_control *cc)
+ unsigned long start_addr, struct collapse_control *cc,
+ unsigned long enabled_orders)
{
const unsigned int max_ptes_shared = collapse_max_ptes_shared(cc, HPAGE_PMD_ORDER);
const unsigned int max_ptes_swap = collapse_max_ptes_swap(cc, HPAGE_PMD_ORDER);
unsigned int max_ptes_none = collapse_max_ptes_none(cc, vma, HPAGE_PMD_ORDER);
- enum tva_type tva_flags = cc->policy.tva_type;
struct mm_struct *mm = vma->vm_mm;
pmd_t *pmd;
pte_t *pte, *_pte, pteval;
@@ -1593,7 +1593,6 @@ static enum scan_result collapse_scan_an
struct folio *folio = NULL;
unsigned long failed_pfn = -1;
unsigned long addr;
- unsigned long enabled_orders;
spinlock_t *ptl;
int node = NUMA_NO_NODE, unmapped = 0;
@@ -1607,8 +1606,6 @@ static enum scan_result collapse_scan_an
collapse_scan_reset(cc);
- enabled_orders = collapse_possible_orders(vma, vma->vm_flags, tva_flags);
-
/*
* If PMD is the only enabled order, enforce max_ptes_none, otherwise
* scan all pages to populate the bitmap for mTHP collapse. The bitmap
@@ -2772,7 +2769,8 @@ static void collapse_control_init(struct
}
static enum scan_result collapse_scan_pmd(struct vm_area_struct *vma,
- unsigned long addr, struct collapse_control *cc)
+ unsigned long addr, struct collapse_control *cc,
+ unsigned long orders)
{
enum scan_result result;
pgoff_t pgoff;
@@ -2785,7 +2783,7 @@ static enum scan_result collapse_scan_pm
}
if (vma_is_anonymous(vma))
- return collapse_scan_anon_pmd(vma, addr, cc);
+ return collapse_scan_anon_pmd(vma, addr, cc, orders);
pgoff = linear_page_index(vma, addr);
result = collapse_scan_file(vma->vm_mm, addr, vma->vm_file, pgoff, cc);
@@ -2895,15 +2893,17 @@ static void collapse_scan_mm_slot(unsign
vma_iter_init(&vmi, mm, khugepaged_scan.address);
for_each_vma(vmi, vma) {
- unsigned long hstart, hend;
+ unsigned long hstart, hend, orders;
cond_resched();
if (unlikely(collapse_test_exit_or_disable(mm))) {
cc->progress++;
break;
}
- if (!collapse_possible_orders(vma, vma->vm_flags,
- TVA_KHUGEPAGED)) {
+ /* One mask for the whole VMA */
+ orders = collapse_possible_orders(vma, vma->vm_flags,
+ TVA_KHUGEPAGED);
+ if (!orders) {
cc->progress++;
continue;
}
@@ -2932,7 +2932,7 @@ static void collapse_scan_mm_slot(unsign
/* move to next address */
khugepaged_scan.address += HPAGE_PMD_SIZE;
- *result = collapse_scan_pmd(vma, addr, cc);
+ *result = collapse_scan_pmd(vma, addr, cc, orders);
/* Nothing to do here, and the lock is still ours */
if (*result != SCAN_SUCCEED &&
*result != SCAN_PTE_MAPPED_HUGEPAGE) {
@@ -3214,14 +3214,16 @@ int madvise_collapse(struct vm_area_stru
{
struct collapse_control *cc;
struct mm_struct *mm = vma->vm_mm;
- unsigned long hstart, hend, addr;
+ unsigned long hstart, hend, addr, orders;
enum scan_result last_fail = SCAN_FAIL;
int thps = 0;
BUG_ON(vma->vm_start > start);
BUG_ON(vma->vm_end < end);
- if (!collapse_possible_orders(vma, vma->vm_flags, TVA_FORCED_COLLAPSE))
+ orders = collapse_possible_orders(vma, vma->vm_flags,
+ TVA_FORCED_COLLAPSE);
+ if (!orders)
return -EINVAL;
hstart = ALIGN(start, HPAGE_PMD_SIZE);
@@ -3259,9 +3261,11 @@ int madvise_collapse(struct vm_area_stru
}
vma = found;
hend = min(hend, vma->vm_end & HPAGE_PMD_MASK);
+ orders = collapse_possible_orders(vma, vma->vm_flags,
+ TVA_FORCED_COLLAPSE);
}
- result = collapse_scan_pmd(vma, addr, cc);
+ result = collapse_scan_pmd(vma, addr, cc, orders);
/* Nothing to do here, and the lock is still ours */
if (result != SCAN_SUCCEED && result != SCAN_PTE_MAPPED_HUGEPAGE)
goto tally;
_
Patches currently in -mm which might be from kas@kernel.org are
mm-huge_memory-do-not-touch-frozen-folios-in-deferred_split_isolate.patch
mm-huge_memory-dequeue-the-deferred-split-after-the-split-freeze.patch
mm-huge_memory-add-folio_reset_partially_mapped.patch
mm-khugepaged-drop-redundant-mm_struct-pin-in-madvise_collapse.patch
mm-khugepaged-count-collapses-where-khugepaged-makes-them.patch
mm-khugepaged-rename-mthp_present_ptes-bitmap-to-eligible_ptes.patch
mm-collapse-add-collapseh-for-the-collapse-interface.patch
mm-collapse-state-what-a-collapse-may-do-in-the-policy.patch
mm-collapse-drop-the-collapse_possible-wrapper.patch
mm-collapse-name-the-per-table-scan-reset-for-what-it-resets.patch
mm-collapse-call-collapse_file-from-collapse_single_pmd.patch
mm-collapse-separate-scanning-a-pte-table-from-collapsing-it.patch
mm-collapse-open-code-collapse_single_pmd-in-its-two-callers.patch
mm-collapse-work-out-the-orders-a-vma-allows-once-per-vma.patch
mm-collapse-declare-the-collapse-interface-in-collapseh.patch
mm-collapse-implement-madv_collapse-in-madvisec.patch
selftests-mm-raise-the-khugepaged-test-case-cap.patch
selftests-mm-skip-collapse_compound_extreme-where-the-pmd-is-too-large.patch
selftests-mm-scale-khugepageds-collapse-wait-with-the-pmd-size.patch
selftests-mm-skip-khugepaged-page-cache-cases-without-a-pmd-folio.patch
selftests-mm-make-the-swap-cases-swapout-reliable.patch
selftests-mm-stop-khugepaged-during-the-madv_collapse-cases.patch
selftests-mm-move-is_backed_by_folio-into-vm_util.patch
selftests-mm-add-folio-order-check-for-address-ranges.patch
selftests-mm-add-folio-order-detection-self-check.patch
selftests-mm-add-khugepaged-completion-barrier-helper.patch
selftests-mm-add-order-parameterized-khugepaged-collapse-cases.patch
selftests-mm-parameterize-the-mixed-source-collapse-case-by-source-order.patch
selftests-mm-cover-a-shared-source-collapse-write-race.patch
selftests-mm-run-every-supported-collapse-order-by-default.patch
selftests-mm-check-that-one-khugepaged-pass-collapses-one-window.patch
selftests-mm-add-khugepaged-race-harness.patch
selftests-mm-race-the-collapse-of-windows-with-holes.patch
selftests-mm-add-memory-pressure-threads-to-the-khugepaged-race-harness.patch
selftests-mm-zap-whole-pte-tables-in-the-khugepaged-race-harness.patch
^ permalink raw reply [flat|nested] 2+ messages in thread* + mm-collapse-work-out-the-orders-a-vma-allows-once-per-vma.patch added to mm-unstable branch
@ 2026-09-16 22:49 Andrew Morton
0 siblings, 0 replies; 2+ messages in thread
From: Andrew Morton @ 2026-09-16 22:49 UTC (permalink / raw)
To: mm-commits, kas, akpm
The patch titled
Subject: mm/collapse: work out the orders a VMA allows once per VMA
has been added to the -mm mm-unstable branch. Its filename is
mm-collapse-work-out-the-orders-a-vma-allows-once-per-vma.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-collapse-work-out-the-orders-a-vma-allows-once-per-vma.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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: "Kiryl Shutsemau (Meta)" <kas@kernel.org>
Subject: mm/collapse: work out the orders a VMA allows once per VMA
Date: Wed, 16 Sep 2026 10:31:37 +0100
The scan asked collapse_possible_orders() for every PTE table, for an
answer that is a property of the VMA. Both callers walk a VMA a table at
a time, so let them work it out once and pass the mask in. It is only
good while the lock that produced it is held, so madvise_collapse() takes
it again after every collapse.
The mask is then sampled once per VMA rather than once per table. A thp
enabled knob written during a walk takes effect one VMA later, and cannot
widen a collapse: hugepage_vma_revalidate() tests the order again under
the lock the collapse retakes.
Assisted-by: LLM
Link: https://lore.kernel.org/20260916093145.4022188-11-kirill@shutemov.name
Signed-off-by: Kiryl Shutsemau (Meta) <kas@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Zi Yan <ziy@nvidia.com>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Barry Song <baohua@kernel.org>
Cc: David Hildenbrand <david@kernel.org>
Cc: Dev Jain <dev.jain@arm.com>
Cc: Jann Horn <jannh@google.com>
Cc: Lance Yang <lance.yang@linux.dev>
Cc: Liam R. Howlett <liam@infradead.org>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
---
mm/khugepaged.c | 32 ++++++++++++++++++--------------
1 file changed, 18 insertions(+), 14 deletions(-)
--- a/mm/khugepaged.c~mm-collapse-work-out-the-orders-a-vma-allows-once-per-vma
+++ a/mm/khugepaged.c
@@ -1549,12 +1549,12 @@ done:
}
static enum scan_result collapse_scan_anon_pmd(struct vm_area_struct *vma,
- unsigned long start_addr, struct collapse_control *cc)
+ unsigned long start_addr, struct collapse_control *cc,
+ unsigned long enabled_orders)
{
const unsigned int max_ptes_shared = collapse_max_ptes_shared(cc, HPAGE_PMD_ORDER);
const unsigned int max_ptes_swap = collapse_max_ptes_swap(cc, HPAGE_PMD_ORDER);
unsigned int max_ptes_none = collapse_max_ptes_none(cc, vma, HPAGE_PMD_ORDER);
- enum tva_type tva_flags = cc->policy.tva_type;
struct mm_struct *mm = vma->vm_mm;
pmd_t *pmd;
pte_t *pte, *_pte, pteval;
@@ -1565,7 +1565,6 @@ static enum scan_result collapse_scan_an
struct folio *folio = NULL;
unsigned long failed_pfn = -1;
unsigned long addr;
- unsigned long enabled_orders;
spinlock_t *ptl;
int node = NUMA_NO_NODE, unmapped = 0;
@@ -1579,8 +1578,6 @@ static enum scan_result collapse_scan_an
collapse_scan_reset(cc);
- enabled_orders = collapse_possible_orders(vma, vma->vm_flags, tva_flags);
-
/*
* If PMD is the only enabled order, enforce max_ptes_none, otherwise
* scan all pages to populate the bitmap for mTHP collapse. The bitmap
@@ -2758,7 +2755,8 @@ static void collapse_control_release(str
}
static enum scan_result collapse_scan_pmd(struct vm_area_struct *vma,
- unsigned long addr, struct collapse_control *cc)
+ unsigned long addr, struct collapse_control *cc,
+ unsigned long orders)
{
enum scan_result result;
pgoff_t pgoff;
@@ -2768,7 +2766,7 @@ static enum scan_result collapse_scan_pm
collapse_put_scan_file(cc);
if (vma_is_anonymous(vma))
- return collapse_scan_anon_pmd(vma, addr, cc);
+ return collapse_scan_anon_pmd(vma, addr, cc, orders);
pgoff = linear_page_index(vma, addr);
result = collapse_scan_file(vma->vm_mm, addr, vma->vm_file, pgoff, cc);
@@ -2878,15 +2876,17 @@ static void collapse_scan_mm_slot(unsign
vma_iter_init(&vmi, mm, khugepaged_scan.address);
for_each_vma(vmi, vma) {
- unsigned long hstart, hend;
+ unsigned long hstart, hend, orders;
cond_resched();
if (unlikely(collapse_test_exit_or_disable(mm))) {
cc->progress++;
break;
}
- if (!collapse_possible_orders(vma, vma->vm_flags,
- TVA_KHUGEPAGED)) {
+ /* One mask for the whole VMA */
+ orders = collapse_possible_orders(vma, vma->vm_flags,
+ cc->policy.tva_type);
+ if (!orders) {
cc->progress++;
continue;
}
@@ -2915,7 +2915,7 @@ static void collapse_scan_mm_slot(unsign
/* move to next address */
khugepaged_scan.address += HPAGE_PMD_SIZE;
- *result = collapse_scan_pmd(vma, addr, cc);
+ *result = collapse_scan_pmd(vma, addr, cc, orders);
/* Nothing to do here, and the lock is still ours */
if (*result != SCAN_SUCCEED &&
*result != SCAN_PTE_MAPPED_HUGEPAGE) {
@@ -3200,14 +3200,16 @@ int madvise_collapse(struct vm_area_stru
{
struct collapse_control *cc;
struct mm_struct *mm = vma->vm_mm;
- unsigned long hstart, hend, addr;
+ unsigned long hstart, hend, addr, orders;
enum scan_result last_fail = SCAN_FAIL;
int thps = 0;
BUG_ON(vma->vm_start > start);
BUG_ON(vma->vm_end < end);
- if (!collapse_possible_orders(vma, vma->vm_flags, TVA_FORCED_COLLAPSE))
+ orders = collapse_possible_orders(vma, vma->vm_flags,
+ TVA_FORCED_COLLAPSE);
+ if (!orders)
return -EINVAL;
hstart = ALIGN(start, HPAGE_PMD_SIZE);
@@ -3245,9 +3247,11 @@ int madvise_collapse(struct vm_area_stru
}
vma = found;
hend = min(hend, vma->vm_end & HPAGE_PMD_MASK);
+ orders = collapse_possible_orders(vma, vma->vm_flags,
+ cc->policy.tva_type);
}
- result = collapse_scan_pmd(vma, addr, cc);
+ result = collapse_scan_pmd(vma, addr, cc, orders);
/* Nothing to do here, and the lock is still ours */
if (result != SCAN_SUCCEED && result != SCAN_PTE_MAPPED_HUGEPAGE)
goto tally;
_
Patches currently in -mm which might be from kas@kernel.org are
mm-huge_memory-do-not-touch-frozen-folios-in-deferred_split_isolate.patch
mm-huge_memory-dequeue-the-deferred-split-after-the-split-freeze.patch
mm-huge_memory-add-folio_reset_partially_mapped.patch
mm-khugepaged-drop-redundant-mm_struct-pin-in-madvise_collapse.patch
mm-khugepaged-count-collapses-where-khugepaged-makes-them.patch
mm-khugepaged-rename-mthp_present_ptes-bitmap-to-eligible_ptes.patch
mm-collapse-add-collapseh-for-the-collapse-interface.patch
mm-collapse-state-what-a-collapse-may-do-in-the-policy.patch
mm-collapse-drop-the-collapse_possible-wrapper.patch
mm-collapse-name-the-per-table-scan-reset-for-what-it-resets.patch
mm-collapse-separate-scanning-a-pte-table-from-collapsing-it.patch
mm-collapse-open-code-collapse_single_pmd-in-its-two-callers.patch
mm-collapse-work-out-the-orders-a-vma-allows-once-per-vma.patch
mm-collapse-declare-the-collapse-interface-in-collapseh.patch
mm-collapse-implement-madv_collapse-in-madvisec.patch
^ permalink raw reply [flat|nested] 2+ messages in thread
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