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Message-ID: <20250714003207.113275-14-npache@redhat.com>
Date: Sun, 13 Jul 2025 18:32:06 -0600
From: Nico Pache <npache@...hat.com>
To: linux-mm@...ck.org,
linux-doc@...r.kernel.org,
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Subject: [PATCH v9 13/14] khugepaged: add per-order mTHP khugepaged stats
With mTHP support inplace, let add the per-order mTHP stats for
exceeding NONE, SWAP, and SHARED.
Signed-off-by: Nico Pache <npache@...hat.com>
---
Documentation/admin-guide/mm/transhuge.rst | 17 +++++++++++++++++
include/linux/huge_mm.h | 3 +++
mm/huge_memory.c | 7 +++++++
mm/khugepaged.c | 15 ++++++++++++---
4 files changed, 39 insertions(+), 3 deletions(-)
diff --git a/Documentation/admin-guide/mm/transhuge.rst b/Documentation/admin-guide/mm/transhuge.rst
index 2c523dce6bc7..28c8af61efba 100644
--- a/Documentation/admin-guide/mm/transhuge.rst
+++ b/Documentation/admin-guide/mm/transhuge.rst
@@ -658,6 +658,23 @@ nr_anon_partially_mapped
an anonymous THP as "partially mapped" and count it here, even though it
is not actually partially mapped anymore.
+collapse_exceed_swap_pte
+ The number of anonymous THP which contain at least one swap PTE.
+ Currently khugepaged does not support collapsing mTHP regions that
+ contain a swap PTE.
+
+collapse_exceed_none_pte
+ The number of anonymous THP which have exceeded the none PTE threshold.
+ With mTHP collapse, a bitmap is used to gather the state of a PMD region
+ and is then recursively checked from largest to smallest order against
+ the scaled max_ptes_none count. This counter indicates that the next
+ enabled order will be checked.
+
+collapse_exceed_shared_pte
+ The number of anonymous THP which contain at least one shared PTE.
+ Currently khugepaged does not support collapsing mTHP regions that
+ contain a shared PTE.
+
As the system ages, allocating huge pages may be expensive as the
system uses memory compaction to copy data around memory to free a
huge page for use. There are some counters in ``/proc/vmstat`` to help
diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
index 4042078e8cc9..e0a27f80f390 100644
--- a/include/linux/huge_mm.h
+++ b/include/linux/huge_mm.h
@@ -141,6 +141,9 @@ enum mthp_stat_item {
MTHP_STAT_SPLIT_DEFERRED,
MTHP_STAT_NR_ANON,
MTHP_STAT_NR_ANON_PARTIALLY_MAPPED,
+ MTHP_STAT_COLLAPSE_EXCEED_SWAP,
+ MTHP_STAT_COLLAPSE_EXCEED_NONE,
+ MTHP_STAT_COLLAPSE_EXCEED_SHARED,
__MTHP_STAT_COUNT
};
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index e2ed9493df77..57e5699cf638 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -632,6 +632,10 @@ DEFINE_MTHP_STAT_ATTR(split_failed, MTHP_STAT_SPLIT_FAILED);
DEFINE_MTHP_STAT_ATTR(split_deferred, MTHP_STAT_SPLIT_DEFERRED);
DEFINE_MTHP_STAT_ATTR(nr_anon, MTHP_STAT_NR_ANON);
DEFINE_MTHP_STAT_ATTR(nr_anon_partially_mapped, MTHP_STAT_NR_ANON_PARTIALLY_MAPPED);
+DEFINE_MTHP_STAT_ATTR(collapse_exceed_swap_pte, MTHP_STAT_COLLAPSE_EXCEED_SWAP);
+DEFINE_MTHP_STAT_ATTR(collapse_exceed_none_pte, MTHP_STAT_COLLAPSE_EXCEED_NONE);
+DEFINE_MTHP_STAT_ATTR(collapse_exceed_shared_pte, MTHP_STAT_COLLAPSE_EXCEED_SHARED);
+
static struct attribute *anon_stats_attrs[] = {
&anon_fault_alloc_attr.attr,
@@ -648,6 +652,9 @@ static struct attribute *anon_stats_attrs[] = {
&split_deferred_attr.attr,
&nr_anon_attr.attr,
&nr_anon_partially_mapped_attr.attr,
+ &collapse_exceed_swap_pte_attr.attr,
+ &collapse_exceed_none_pte_attr.attr,
+ &collapse_exceed_shared_pte_attr.attr,
NULL,
};
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index d0c99b86b304..8a5873d0a23a 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -594,7 +594,10 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
continue;
} else {
result = SCAN_EXCEED_NONE_PTE;
- count_vm_event(THP_SCAN_EXCEED_NONE_PTE);
+ if (order == HPAGE_PMD_ORDER)
+ count_vm_event(THP_SCAN_EXCEED_NONE_PTE);
+ else
+ count_mthp_stat(order, MTHP_STAT_COLLAPSE_EXCEED_NONE);
goto out;
}
}
@@ -623,8 +626,14 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
/* See khugepaged_scan_pmd(). */
if (folio_maybe_mapped_shared(folio)) {
++shared;
- if (order != HPAGE_PMD_ORDER || (cc->is_khugepaged &&
- shared > khugepaged_max_ptes_shared)) {
+ if (order != HPAGE_PMD_ORDER) {
+ result = SCAN_EXCEED_SHARED_PTE;
+ count_mthp_stat(order, MTHP_STAT_COLLAPSE_EXCEED_SHARED);
+ goto out;
+ }
+
+ if (cc->is_khugepaged &&
+ shared > khugepaged_max_ptes_shared) {
result = SCAN_EXCEED_SHARED_PTE;
count_vm_event(THP_SCAN_EXCEED_SHARED_PTE);
goto out;
--
2.50.0
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