| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-ID: <20260122192841.128719-11-npache@redhat.com>
Date: Thu, 22 Jan 2026 12:28:35 -0700
From: Nico Pache <npache@...hat.com>
To: linux-mm@...ck.org,
linux-doc@...r.kernel.org,
linux-kernel@...r.kernel.org,
linux-trace-kernel@...r.kernel.org
Cc: npache@...hat.com,
akpm@...ux-foundation.org,
david@...nel.org,
lorenzo.stoakes@...cle.com,
ziy@...dia.com,
baolin.wang@...ux.alibaba.com,
Liam.Howlett@...cle.com,
ryan.roberts@....com,
dev.jain@....com,
baohua@...nel.org,
lance.yang@...ux.dev,
vbabka@...e.cz,
rppt@...nel.org,
surenb@...gle.com,
mhocko@...e.com,
corbet@....net,
rostedt@...dmis.org,
mhiramat@...nel.org,
mathieu.desnoyers@...icios.com,
matthew.brost@...el.com,
joshua.hahnjy@...il.com,
rakie.kim@...com,
byungchul@...com,
gourry@...rry.net,
ying.huang@...ux.alibaba.com,
apopple@...dia.com,
jannh@...gle.com,
pfalcato@...e.de,
jackmanb@...gle.com,
hannes@...xchg.org,
willy@...radead.org,
peterx@...hat.com,
wangkefeng.wang@...wei.com,
usamaarif642@...il.com,
sunnanyong@...wei.com,
vishal.moola@...il.com,
thomas.hellstrom@...ux.intel.com,
yang@...amperecomputing.com,
kas@...nel.org,
aarcange@...hat.com,
raquini@...hat.com,
anshuman.khandual@....com,
catalin.marinas@....com,
tiwai@...e.de,
will@...nel.org,
dave.hansen@...ux.intel.com,
jack@...e.cz,
cl@...two.org,
jglisse@...gle.com,
zokeefe@...gle.com,
rientjes@...gle.com,
rdunlap@...radead.org,
hughd@...gle.com,
richard.weiyang@...il.com
Subject: [PATCH mm-unstable v14 10/16] khugepaged: add per-order mTHP collapse failure statistics
Add three new mTHP statistics to track collapse failures for different
orders when encountering swap PTEs, excessive none PTEs, and shared PTEs:
- collapse_exceed_swap_pte: Increment when mTHP collapse fails due to swap
PTEs
- collapse_exceed_none_pte: Counts when mTHP collapse fails due to
exceeding the none PTE threshold for the given order
- collapse_exceed_shared_pte: Counts when mTHP collapse fails due to shared
PTEs
These statistics complement the existing THP_SCAN_EXCEED_* events by
providing per-order granularity for mTHP collapse attempts. The stats are
exposed via sysfs under
`/sys/kernel/mm/transparent_hugepage/hugepages-*/stats/` for each
supported hugepage size.
As we currently dont support collapsing mTHPs that contain a swap or
shared entry, those statistics keep track of how often we are
encountering failed mTHP collapses due to these restrictions.
Reviewed-by: Baolin Wang <baolin.wang@...ux.alibaba.com>
Signed-off-by: Nico Pache <npache@...hat.com>
---
Documentation/admin-guide/mm/transhuge.rst | 24 ++++++++++++++++++++++
include/linux/huge_mm.h | 3 +++
mm/huge_memory.c | 7 +++++++
mm/khugepaged.c | 16 ++++++++++++---
4 files changed, 47 insertions(+), 3 deletions(-)
diff --git a/Documentation/admin-guide/mm/transhuge.rst b/Documentation/admin-guide/mm/transhuge.rst
index c51932e6275d..eebb1f6bbc6c 100644
--- a/Documentation/admin-guide/mm/transhuge.rst
+++ b/Documentation/admin-guide/mm/transhuge.rst
@@ -714,6 +714,30 @@ 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_none_pte
+ The number of collapse attempts that failed due to exceeding the
+ max_ptes_none threshold. For mTHP collapse, Currently only max_ptes_none
+ values of 0 and (HPAGE_PMD_NR - 1) are supported. Any other value will
+ emit a warning and no mTHP collapse will be attempted. khugepaged will
+ try to collapse to the largest enabled (m)THP size; if it fails, it will
+ try the next lower enabled mTHP size. This counter records the number of
+ times a collapse attempt was skipped for exceeding the max_ptes_none
+ threshold, and khugepaged will move on to the next available mTHP size.
+
+collapse_exceed_swap_pte
+ The number of anonymous mTHP PTE ranges which were unable to collapse due
+ to containing at least one swap PTE. Currently khugepaged does not
+ support collapsing mTHP regions that contain a swap PTE. This counter can
+ be used to monitor the number of khugepaged mTHP collapses that failed
+ due to the presence of a swap PTE.
+
+collapse_exceed_shared_pte
+ The number of anonymous mTHP PTE ranges which were unable to collapse due
+ to containing at least one shared PTE. Currently khugepaged does not
+ support collapsing mTHP PTE ranges that contain a shared PTE. This
+ counter can be used to monitor the number of khugepaged mTHP collapses
+ that failed due to the presence of 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 9941fc6d7bd8..e8777bb2347d 100644
--- a/include/linux/huge_mm.h
+++ b/include/linux/huge_mm.h
@@ -144,6 +144,9 @@ 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 00fc92062d70..7c0b072fc6b2 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -639,6 +639,10 @@ 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,
@@ -655,6 +659,9 @@ 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 8bb70e1401ad..96f1c28646ba 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -602,7 +602,9 @@ static enum scan_result __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 (is_pmd_order(order))
+ count_vm_event(THP_SCAN_EXCEED_NONE_PTE);
+ count_mthp_stat(order, MTHP_STAT_COLLAPSE_EXCEED_NONE);
goto out;
}
}
@@ -632,10 +634,17 @@ static enum scan_result __collapse_huge_page_isolate(struct vm_area_struct *vma,
* shared may cause a future higher order collapse on a
* rescan of the same range.
*/
- if (!is_pmd_order(order) || (cc->is_khugepaged &&
- shared > khugepaged_max_ptes_shared)) {
+ if (!is_pmd_order(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);
+ count_mthp_stat(order, MTHP_STAT_COLLAPSE_EXCEED_SHARED);
goto out;
}
}
@@ -1082,6 +1091,7 @@ static enum scan_result __collapse_huge_page_swapin(struct mm_struct *mm,
* range.
*/
if (!is_pmd_order(order)) {
+ count_mthp_stat(order, MTHP_STAT_COLLAPSE_EXCEED_SWAP);
pte_unmap(pte);
mmap_read_unlock(mm);
result = SCAN_EXCEED_SWAP_PTE;
--
2.52.0
Powered by blists - more mailing lists