* [PATCH v6 00/12] khugepaged: mTHP support
@ 2025-05-15 3:03 Nico Pache
2025-05-15 3:03 ` [PATCH v6 01/12] khugepaged: rename hpage_collapse_* to khugepaged_* Nico Pache
2025-05-15 3:21 ` [PATCH v6 00/12] khugepaged: mTHP support Nico Pache
0 siblings, 2 replies; 16+ messages in thread
From: Nico Pache @ 2025-05-15 3:03 UTC (permalink / raw)
To: linux-mm, linux-doc, linux-kernel, linux-trace-kernel
Cc: david, ziy, baolin.wang, lorenzo.stoakes, Liam.Howlett,
ryan.roberts, dev.jain, corbet, rostedt, mhiramat,
mathieu.desnoyers, akpm, baohua, willy, peterx, wangkefeng.wang,
usamaarif642, sunnanyong, vishal.moola, thomas.hellstrom, yang,
kirill.shutemov, aarcange, raquini, anshuman.khandual,
catalin.marinas, tiwai, will, dave.hansen, jack, cl, jglisse,
surenb, zokeefe, hannes, rientjes, mhocko, rdunlap
The following series provides khugepaged and madvise collapse with the
capability to collapse anonymous memory regions to mTHPs.
To achieve this we generalize the khugepaged functions to no longer depend
on PMD_ORDER. Then during the PMD scan, we keep track of chunks of pages
(defined by KHUGEPAGED_MTHP_MIN_ORDER) that are utilized. This info is
tracked using a bitmap. After the PMD scan is done, we do binary recursion
on the bitmap to find the optimal mTHP sizes for the PMD range. The
restriction on max_ptes_none is removed during the scan, to make sure we
account for the whole PMD range. When no mTHP size is enabled, the legacy
behavior of khugepaged is maintained. max_ptes_none will be scaled by the
attempted collapse order to determine how full a THP must be to be
eligible. If a mTHP collapse is attempted, but contains swapped out, or
shared pages, we dont perform the collapse.
With the default max_ptes_none=511, the code should keep its most of its
original behavior. To exercise mTHP collapse we need to set
max_ptes_none<=255. With max_ptes_none > HPAGE_PMD_NR/2 you will
experience collapse "creep" and constantly promote mTHPs to the next
available size. This is due the fact that it will introduce at least 2x
the number of pages, and on a future scan will satisfy that condition once
again.
Patch 1: Refactor/rename hpage_collapse
Patch 2: Some refactoring to combine madvise_collapse and khugepaged
Patch 3-5: Generalize khugepaged functions for arbitrary orders
Patch 6-9: The mTHP patches
Patch 10-11: Tracing/stats
Patch 12: Documentation
---------
Testing
---------
- Built for x86_64, aarch64, ppc64le, and s390x
- selftests mm
- I created a test script that I used to push khugepaged to its limits
while monitoring a number of stats and tracepoints. The code is
available here[1] (Run in legacy mode for these changes and set mthp
sizes to inherit)
The summary from my testings was that there was no significant
regression noticed through this test. In some cases my changes had
better collapse latencies, and was able to scan more pages in the same
amount of time/work, but for the most part the results were consistent.
- redis testing. I tested these changes along with my defer changes
(see followup post for more details).
- some basic testing on 64k page size.
- lots of general use.
V6 Changes:
- Dont release the anon_vma_lock early (like in the PMD case), as not all
pages are isolated.
- Define the PTE as null to avoid a uninitilized condition
- minor nits and newline cleanup
- make sure to unmap and unlock the pte for the swapin case
- change the revalidation to always check the PMD order (as this will make
sure that no other VMA spans it)
V5 Changes [2]:
- switched the order of patches 1 and 2
- fixed some edge cases on the unified madvise_collapse and khugepaged
- Explained the "creep" some more in the docs
- fix EXCEED_SHARED vs EXCEED_SWAP accounting issue
- fix potential highmem issue caused by a early unmap of the PTE
V4 Changes:
- Rebased onto mm-unstable
- small changes to Documentation
V3 Changes:
- corrected legacy behavior for khugepaged and madvise_collapse
- added proper mTHP stat tracking
- Minor changes to prevent a nested lock on non-split-lock arches
- Took Devs version of alloc_charge_folio as it has the proper stats
- Skip cases were trying to collapse to a lower order would still fail
- Fixed cases were the bitmap was not being updated properly
- Moved Documentation update to this series instead of the defer set
- Minor bugs discovered during testing and review
- Minor "nit" cleanup
V2 Changes:
- Minor bug fixes discovered during review and testing
- removed dynamic allocations for bitmaps, and made them stack based
- Adjusted bitmap offset from u8 to u16 to support 64k pagesize.
- Updated trace events to include collapsing order info.
- Scaled max_ptes_none by order rather than scaling to a 0-100 scale.
- No longer require a chunk to be fully utilized before setting the bit.
Use the same max_ptes_none scaling principle to achieve this.
- Skip mTHP collapse that requires swapin or shared handling. This helps
prevent some of the "creep" that was discovered in v1.
[1] - https://gitlab.com/npache/khugepaged_mthp_test
[2] - https://lore.kernel.org/all/20250428181218.85925-1-npache@redhat.com/
Dev Jain (1):
khugepaged: generalize alloc_charge_folio()
Nico Pache (11):
khugepaged: rename hpage_collapse_* to khugepaged_*
introduce khugepaged_collapse_single_pmd to unify khugepaged and
madvise_collapse
khugepaged: generalize hugepage_vma_revalidate for mTHP support
khugepaged: generalize __collapse_huge_page_* for mTHP support
khugepaged: introduce khugepaged_scan_bitmap for mTHP support
khugepaged: add mTHP support
khugepaged: skip collapsing mTHP to smaller orders
khugepaged: avoid unnecessary mTHP collapse attempts
khugepaged: improve tracepoints for mTHP orders
khugepaged: add per-order mTHP khugepaged stats
Documentation: mm: update the admin guide for mTHP collapse
Documentation/admin-guide/mm/transhuge.rst | 14 +-
include/linux/huge_mm.h | 5 +
include/linux/khugepaged.h | 4 +
include/trace/events/huge_memory.h | 34 +-
mm/huge_memory.c | 11 +
mm/khugepaged.c | 472 ++++++++++++++-------
6 files changed, 382 insertions(+), 158 deletions(-)
--
2.49.0
^ permalink raw reply [flat|nested] 16+ messages in thread
* [PATCH v6 01/12] khugepaged: rename hpage_collapse_* to khugepaged_*
2025-05-15 3:03 [PATCH v6 00/12] khugepaged: mTHP support Nico Pache
@ 2025-05-15 3:03 ` Nico Pache
2025-05-15 3:03 ` [PATCH v6 02/12] introduce khugepaged_collapse_single_pmd to unify khugepaged and madvise_collapse Nico Pache
2025-05-15 3:21 ` [PATCH v6 00/12] khugepaged: mTHP support Nico Pache
1 sibling, 1 reply; 16+ messages in thread
From: Nico Pache @ 2025-05-15 3:03 UTC (permalink / raw)
To: linux-mm, linux-doc, linux-kernel, linux-trace-kernel
Cc: david, ziy, baolin.wang, lorenzo.stoakes, Liam.Howlett,
ryan.roberts, dev.jain, corbet, rostedt, mhiramat,
mathieu.desnoyers, akpm, baohua, willy, peterx, wangkefeng.wang,
usamaarif642, sunnanyong, vishal.moola, thomas.hellstrom, yang,
kirill.shutemov, aarcange, raquini, anshuman.khandual,
catalin.marinas, tiwai, will, dave.hansen, jack, cl, jglisse,
surenb, zokeefe, hannes, rientjes, mhocko, rdunlap
functions in khugepaged.c use a mix of hpage_collapse and khugepaged
as the function prefix.
rename all of them to khugepaged to keep things consistent and slightly
shorten the function names.
Reviewed-by: Zi Yan <ziy@nvidia.com>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Signed-off-by: Nico Pache <npache@redhat.com>
---
mm/khugepaged.c | 42 +++++++++++++++++++++---------------------
1 file changed, 21 insertions(+), 21 deletions(-)
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index cdf5a581368b..806bcd8c5185 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -402,14 +402,14 @@ void __init khugepaged_destroy(void)
kmem_cache_destroy(mm_slot_cache);
}
-static inline int hpage_collapse_test_exit(struct mm_struct *mm)
+static inline int khugepaged_test_exit(struct mm_struct *mm)
{
return atomic_read(&mm->mm_users) == 0;
}
-static inline int hpage_collapse_test_exit_or_disable(struct mm_struct *mm)
+static inline int khugepaged_test_exit_or_disable(struct mm_struct *mm)
{
- return hpage_collapse_test_exit(mm) ||
+ return khugepaged_test_exit(mm) ||
test_bit(MMF_DISABLE_THP, &mm->flags);
}
@@ -444,7 +444,7 @@ void __khugepaged_enter(struct mm_struct *mm)
int wakeup;
/* __khugepaged_exit() must not run from under us */
- VM_BUG_ON_MM(hpage_collapse_test_exit(mm), mm);
+ VM_BUG_ON_MM(khugepaged_test_exit(mm), mm);
if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE, &mm->flags)))
return;
@@ -503,7 +503,7 @@ void __khugepaged_exit(struct mm_struct *mm)
} else if (mm_slot) {
/*
* This is required to serialize against
- * hpage_collapse_test_exit() (which is guaranteed to run
+ * khugepaged_test_exit() (which is guaranteed to run
* under mmap sem read mode). Stop here (after we return all
* pagetables will be destroyed) until khugepaged has finished
* working on the pagetables under the mmap_lock.
@@ -851,7 +851,7 @@ struct collapse_control khugepaged_collapse_control = {
.is_khugepaged = true,
};
-static bool hpage_collapse_scan_abort(int nid, struct collapse_control *cc)
+static bool khugepaged_scan_abort(int nid, struct collapse_control *cc)
{
int i;
@@ -886,7 +886,7 @@ static inline gfp_t alloc_hugepage_khugepaged_gfpmask(void)
}
#ifdef CONFIG_NUMA
-static int hpage_collapse_find_target_node(struct collapse_control *cc)
+static int khugepaged_find_target_node(struct collapse_control *cc)
{
int nid, target_node = 0, max_value = 0;
@@ -905,7 +905,7 @@ static int hpage_collapse_find_target_node(struct collapse_control *cc)
return target_node;
}
#else
-static int hpage_collapse_find_target_node(struct collapse_control *cc)
+static int khugepaged_find_target_node(struct collapse_control *cc)
{
return 0;
}
@@ -925,7 +925,7 @@ static int hugepage_vma_revalidate(struct mm_struct *mm, unsigned long address,
struct vm_area_struct *vma;
unsigned long tva_flags = cc->is_khugepaged ? TVA_ENFORCE_SYSFS : 0;
- if (unlikely(hpage_collapse_test_exit_or_disable(mm)))
+ if (unlikely(khugepaged_test_exit_or_disable(mm)))
return SCAN_ANY_PROCESS;
*vmap = vma = find_vma(mm, address);
@@ -992,7 +992,7 @@ static int check_pmd_still_valid(struct mm_struct *mm,
/*
* Bring missing pages in from swap, to complete THP collapse.
- * Only done if hpage_collapse_scan_pmd believes it is worthwhile.
+ * Only done if khugepaged_scan_pmd believes it is worthwhile.
*
* Called and returns without pte mapped or spinlocks held.
* Returns result: if not SCAN_SUCCEED, mmap_lock has been released.
@@ -1078,7 +1078,7 @@ static int alloc_charge_folio(struct folio **foliop, struct mm_struct *mm,
{
gfp_t gfp = (cc->is_khugepaged ? alloc_hugepage_khugepaged_gfpmask() :
GFP_TRANSHUGE);
- int node = hpage_collapse_find_target_node(cc);
+ int node = khugepaged_find_target_node(cc);
struct folio *folio;
folio = __folio_alloc(gfp, HPAGE_PMD_ORDER, node, &cc->alloc_nmask);
@@ -1264,7 +1264,7 @@ static int collapse_huge_page(struct mm_struct *mm, unsigned long address,
return result;
}
-static int hpage_collapse_scan_pmd(struct mm_struct *mm,
+static int khugepaged_scan_pmd(struct mm_struct *mm,
struct vm_area_struct *vma,
unsigned long address, bool *mmap_locked,
struct collapse_control *cc)
@@ -1378,7 +1378,7 @@ static int hpage_collapse_scan_pmd(struct mm_struct *mm,
* hit record.
*/
node = folio_nid(folio);
- if (hpage_collapse_scan_abort(node, cc)) {
+ if (khugepaged_scan_abort(node, cc)) {
result = SCAN_SCAN_ABORT;
goto out_unmap;
}
@@ -1447,7 +1447,7 @@ static void collect_mm_slot(struct khugepaged_mm_slot *mm_slot)
lockdep_assert_held(&khugepaged_mm_lock);
- if (hpage_collapse_test_exit(mm)) {
+ if (khugepaged_test_exit(mm)) {
/* free mm_slot */
hash_del(&slot->hash);
list_del(&slot->mm_node);
@@ -1740,7 +1740,7 @@ static void retract_page_tables(struct address_space *mapping, pgoff_t pgoff)
if (find_pmd_or_thp_or_none(mm, addr, &pmd) != SCAN_SUCCEED)
continue;
- if (hpage_collapse_test_exit(mm))
+ if (khugepaged_test_exit(mm))
continue;
/*
* When a vma is registered with uffd-wp, we cannot recycle
@@ -2262,7 +2262,7 @@ static int collapse_file(struct mm_struct *mm, unsigned long addr,
return result;
}
-static int hpage_collapse_scan_file(struct mm_struct *mm, unsigned long addr,
+static int khugepaged_scan_file(struct mm_struct *mm, unsigned long addr,
struct file *file, pgoff_t start,
struct collapse_control *cc)
{
@@ -2307,7 +2307,7 @@ static int hpage_collapse_scan_file(struct mm_struct *mm, unsigned long addr,
}
node = folio_nid(folio);
- if (hpage_collapse_scan_abort(node, cc)) {
+ if (khugepaged_scan_abort(node, cc)) {
result = SCAN_SCAN_ABORT;
break;
}
@@ -2391,7 +2391,7 @@ static unsigned int khugepaged_scan_mm_slot(unsigned int pages, int *result,
goto breakouterloop_mmap_lock;
progress++;
- if (unlikely(hpage_collapse_test_exit_or_disable(mm)))
+ if (unlikely(khugepaged_test_exit_or_disable(mm)))
goto breakouterloop;
vma_iter_init(&vmi, mm, khugepaged_scan.address);
@@ -2399,7 +2399,7 @@ static unsigned int khugepaged_scan_mm_slot(unsigned int pages, int *result,
unsigned long hstart, hend;
cond_resched();
- if (unlikely(hpage_collapse_test_exit_or_disable(mm))) {
+ if (unlikely(khugepaged_test_exit_or_disable(mm))) {
progress++;
break;
}
@@ -2421,7 +2421,7 @@ static unsigned int khugepaged_scan_mm_slot(unsigned int pages, int *result,
bool mmap_locked = true;
cond_resched();
- if (unlikely(hpage_collapse_test_exit_or_disable(mm)))
+ if (unlikely(khugepaged_test_exit_or_disable(mm)))
goto breakouterloop;
VM_BUG_ON(khugepaged_scan.address < hstart ||
@@ -2481,7 +2481,7 @@ static unsigned int khugepaged_scan_mm_slot(unsigned int pages, int *result,
* Release the current mm_slot if this mm is about to die, or
* if we scanned all vmas of this mm.
*/
- if (hpage_collapse_test_exit(mm) || !vma) {
+ if (khugepaged_test_exit(mm) || !vma) {
/*
* Make sure that if mm_users is reaching zero while
* khugepaged runs here, khugepaged_exit will find
--
2.49.0
^ permalink raw reply related [flat|nested] 16+ messages in thread
* [PATCH v6 02/12] introduce khugepaged_collapse_single_pmd to unify khugepaged and madvise_collapse
2025-05-15 3:03 ` [PATCH v6 01/12] khugepaged: rename hpage_collapse_* to khugepaged_* Nico Pache
@ 2025-05-15 3:03 ` Nico Pache
2025-05-15 3:03 ` [PATCH v6 03/12] khugepaged: generalize hugepage_vma_revalidate for mTHP support Nico Pache
0 siblings, 1 reply; 16+ messages in thread
From: Nico Pache @ 2025-05-15 3:03 UTC (permalink / raw)
To: linux-mm, linux-doc, linux-kernel, linux-trace-kernel
Cc: david, ziy, baolin.wang, lorenzo.stoakes, Liam.Howlett,
ryan.roberts, dev.jain, corbet, rostedt, mhiramat,
mathieu.desnoyers, akpm, baohua, willy, peterx, wangkefeng.wang,
usamaarif642, sunnanyong, vishal.moola, thomas.hellstrom, yang,
kirill.shutemov, aarcange, raquini, anshuman.khandual,
catalin.marinas, tiwai, will, dave.hansen, jack, cl, jglisse,
surenb, zokeefe, hannes, rientjes, mhocko, rdunlap
The khugepaged daemon and madvise_collapse have two different
implementations that do almost the same thing.
Create khugepaged_collapse_single_pmd to increase code
reuse and create an entry point for future khugepaged changes.
Refactor madvise_collapse and khugepaged_scan_mm_slot to use
the new khugepaged_collapse_single_pmd function.
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Signed-off-by: Nico Pache <npache@redhat.com>
---
mm/khugepaged.c | 96 +++++++++++++++++++++++++------------------------
1 file changed, 49 insertions(+), 47 deletions(-)
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 806bcd8c5185..5457571d505a 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -2353,6 +2353,48 @@ static int khugepaged_scan_file(struct mm_struct *mm, unsigned long addr,
return result;
}
+/*
+ * Try to collapse a single PMD starting at a PMD aligned addr, and return
+ * the results.
+ */
+static int khugepaged_collapse_single_pmd(unsigned long addr,
+ struct vm_area_struct *vma, bool *mmap_locked,
+ struct collapse_control *cc)
+{
+ int result = SCAN_FAIL;
+ struct mm_struct *mm = vma->vm_mm;
+
+ if (IS_ENABLED(CONFIG_SHMEM) && !vma_is_anonymous(vma)) {
+ struct file *file = get_file(vma->vm_file);
+ pgoff_t pgoff = linear_page_index(vma, addr);
+
+ mmap_read_unlock(mm);
+ *mmap_locked = false;
+ result = khugepaged_scan_file(mm, addr, file, pgoff, cc);
+ fput(file);
+ if (result == SCAN_PTE_MAPPED_HUGEPAGE) {
+ mmap_read_lock(mm);
+ *mmap_locked = true;
+ if (khugepaged_test_exit_or_disable(mm)) {
+ result = SCAN_ANY_PROCESS;
+ goto end;
+ }
+ result = collapse_pte_mapped_thp(mm, addr,
+ !cc->is_khugepaged);
+ if (result == SCAN_PMD_MAPPED)
+ result = SCAN_SUCCEED;
+ mmap_read_unlock(mm);
+ *mmap_locked = false;
+ }
+ } else {
+ result = khugepaged_scan_pmd(mm, vma, addr, mmap_locked, cc);
+ }
+ if (cc->is_khugepaged && result == SCAN_SUCCEED)
+ ++khugepaged_pages_collapsed;
+end:
+ return result;
+}
+
static unsigned int khugepaged_scan_mm_slot(unsigned int pages, int *result,
struct collapse_control *cc)
__releases(&khugepaged_mm_lock)
@@ -2427,34 +2469,12 @@ static unsigned int khugepaged_scan_mm_slot(unsigned int pages, int *result,
VM_BUG_ON(khugepaged_scan.address < hstart ||
khugepaged_scan.address + HPAGE_PMD_SIZE >
hend);
- if (!vma_is_anonymous(vma)) {
- struct file *file = get_file(vma->vm_file);
- pgoff_t pgoff = linear_page_index(vma,
- khugepaged_scan.address);
-
- mmap_read_unlock(mm);
- mmap_locked = false;
- *result = hpage_collapse_scan_file(mm,
- khugepaged_scan.address, file, pgoff, cc);
- fput(file);
- if (*result == SCAN_PTE_MAPPED_HUGEPAGE) {
- mmap_read_lock(mm);
- if (hpage_collapse_test_exit_or_disable(mm))
- goto breakouterloop;
- *result = collapse_pte_mapped_thp(mm,
- khugepaged_scan.address, false);
- if (*result == SCAN_PMD_MAPPED)
- *result = SCAN_SUCCEED;
- mmap_read_unlock(mm);
- }
- } else {
- *result = hpage_collapse_scan_pmd(mm, vma,
- khugepaged_scan.address, &mmap_locked, cc);
- }
-
- if (*result == SCAN_SUCCEED)
- ++khugepaged_pages_collapsed;
+ *result = khugepaged_collapse_single_pmd(khugepaged_scan.address,
+ vma, &mmap_locked, cc);
+ /* If we return SCAN_ANY_PROCESS we are holding the mmap_lock */
+ if (*result == SCAN_ANY_PROCESS)
+ goto breakouterloop;
/* move to next address */
khugepaged_scan.address += HPAGE_PMD_SIZE;
progress += HPAGE_PMD_NR;
@@ -2773,36 +2793,18 @@ int madvise_collapse(struct vm_area_struct *vma, struct vm_area_struct **prev,
mmap_assert_locked(mm);
memset(cc->node_load, 0, sizeof(cc->node_load));
nodes_clear(cc->alloc_nmask);
- if (!vma_is_anonymous(vma)) {
- struct file *file = get_file(vma->vm_file);
- pgoff_t pgoff = linear_page_index(vma, addr);
- mmap_read_unlock(mm);
- mmap_locked = false;
- result = hpage_collapse_scan_file(mm, addr, file, pgoff,
- cc);
- fput(file);
- } else {
- result = hpage_collapse_scan_pmd(mm, vma, addr,
- &mmap_locked, cc);
- }
+ result = khugepaged_collapse_single_pmd(addr, vma, &mmap_locked, cc);
+
if (!mmap_locked)
*prev = NULL; /* Tell caller we dropped mmap_lock */
-handle_result:
switch (result) {
case SCAN_SUCCEED:
case SCAN_PMD_MAPPED:
++thps;
break;
case SCAN_PTE_MAPPED_HUGEPAGE:
- BUG_ON(mmap_locked);
- BUG_ON(*prev);
- mmap_read_lock(mm);
- result = collapse_pte_mapped_thp(mm, addr, true);
- mmap_read_unlock(mm);
- goto handle_result;
- /* Whitelisted set of results where continuing OK */
case SCAN_PMD_NULL:
case SCAN_PTE_NON_PRESENT:
case SCAN_PTE_UFFD_WP:
--
2.49.0
^ permalink raw reply related [flat|nested] 16+ messages in thread
* [PATCH v6 03/12] khugepaged: generalize hugepage_vma_revalidate for mTHP support
2025-05-15 3:03 ` [PATCH v6 02/12] introduce khugepaged_collapse_single_pmd to unify khugepaged and madvise_collapse Nico Pache
@ 2025-05-15 3:03 ` Nico Pache
2025-05-15 3:03 ` [PATCH v6 04/12] khugepaged: generalize alloc_charge_folio() Nico Pache
0 siblings, 1 reply; 16+ messages in thread
From: Nico Pache @ 2025-05-15 3:03 UTC (permalink / raw)
To: linux-mm, linux-doc, linux-kernel, linux-trace-kernel
Cc: david, ziy, baolin.wang, lorenzo.stoakes, Liam.Howlett,
ryan.roberts, dev.jain, corbet, rostedt, mhiramat,
mathieu.desnoyers, akpm, baohua, willy, peterx, wangkefeng.wang,
usamaarif642, sunnanyong, vishal.moola, thomas.hellstrom, yang,
kirill.shutemov, aarcange, raquini, anshuman.khandual,
catalin.marinas, tiwai, will, dave.hansen, jack, cl, jglisse,
surenb, zokeefe, hannes, rientjes, mhocko, rdunlap
For khugepaged to support different mTHP orders, we must generalize this
to check if the PMD is not shared by another VMA and the order is
enabled.
No functional change in this patch.
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
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>
---
mm/khugepaged.c | 10 +++++-----
1 file changed, 5 insertions(+), 5 deletions(-)
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 5457571d505a..0c4d6a02d59c 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -920,7 +920,7 @@ static int khugepaged_find_target_node(struct collapse_control *cc)
static int hugepage_vma_revalidate(struct mm_struct *mm, unsigned long address,
bool expect_anon,
struct vm_area_struct **vmap,
- struct collapse_control *cc)
+ struct collapse_control *cc, int order)
{
struct vm_area_struct *vma;
unsigned long tva_flags = cc->is_khugepaged ? TVA_ENFORCE_SYSFS : 0;
@@ -934,7 +934,7 @@ static int hugepage_vma_revalidate(struct mm_struct *mm, unsigned long address,
if (!thp_vma_suitable_order(vma, address, PMD_ORDER))
return SCAN_ADDRESS_RANGE;
- if (!thp_vma_allowable_order(vma, vma->vm_flags, tva_flags, PMD_ORDER))
+ if (!thp_vma_allowable_order(vma, vma->vm_flags, tva_flags, order))
return SCAN_VMA_CHECK;
/*
* Anon VMA expected, the address may be unmapped then
@@ -1130,7 +1130,7 @@ static int collapse_huge_page(struct mm_struct *mm, unsigned long address,
goto out_nolock;
mmap_read_lock(mm);
- result = hugepage_vma_revalidate(mm, address, true, &vma, cc);
+ result = hugepage_vma_revalidate(mm, address, true, &vma, cc, HPAGE_PMD_ORDER);
if (result != SCAN_SUCCEED) {
mmap_read_unlock(mm);
goto out_nolock;
@@ -1164,7 +1164,7 @@ static int collapse_huge_page(struct mm_struct *mm, unsigned long address,
* mmap_lock.
*/
mmap_write_lock(mm);
- result = hugepage_vma_revalidate(mm, address, true, &vma, cc);
+ result = hugepage_vma_revalidate(mm, address, true, &vma, cc, HPAGE_PMD_ORDER);
if (result != SCAN_SUCCEED)
goto out_up_write;
/* check if the pmd is still valid */
@@ -2782,7 +2782,7 @@ int madvise_collapse(struct vm_area_struct *vma, struct vm_area_struct **prev,
mmap_read_lock(mm);
mmap_locked = true;
result = hugepage_vma_revalidate(mm, addr, false, &vma,
- cc);
+ cc, HPAGE_PMD_ORDER);
if (result != SCAN_SUCCEED) {
last_fail = result;
goto out_nolock;
--
2.49.0
^ permalink raw reply related [flat|nested] 16+ messages in thread
* [PATCH v6 04/12] khugepaged: generalize alloc_charge_folio()
2025-05-15 3:03 ` [PATCH v6 03/12] khugepaged: generalize hugepage_vma_revalidate for mTHP support Nico Pache
@ 2025-05-15 3:03 ` Nico Pache
2025-05-15 3:03 ` [PATCH v6 05/12] khugepaged: generalize __collapse_huge_page_* for mTHP support Nico Pache
0 siblings, 1 reply; 16+ messages in thread
From: Nico Pache @ 2025-05-15 3:03 UTC (permalink / raw)
To: linux-mm, linux-doc, linux-kernel, linux-trace-kernel
Cc: david, ziy, baolin.wang, lorenzo.stoakes, Liam.Howlett,
ryan.roberts, dev.jain, corbet, rostedt, mhiramat,
mathieu.desnoyers, akpm, baohua, willy, peterx, wangkefeng.wang,
usamaarif642, sunnanyong, vishal.moola, thomas.hellstrom, yang,
kirill.shutemov, aarcange, raquini, anshuman.khandual,
catalin.marinas, tiwai, will, dave.hansen, jack, cl, jglisse,
surenb, zokeefe, hannes, rientjes, mhocko, rdunlap
From: Dev Jain <dev.jain@arm.com>
Pass order to alloc_charge_folio() and update mTHP statistics.
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Co-developed-by: Nico Pache <npache@redhat.com>
Signed-off-by: Nico Pache <npache@redhat.com>
Signed-off-by: Dev Jain <dev.jain@arm.com>
---
include/linux/huge_mm.h | 2 ++
mm/huge_memory.c | 4 ++++
mm/khugepaged.c | 17 +++++++++++------
3 files changed, 17 insertions(+), 6 deletions(-)
diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
index 2f190c90192d..0bb65bd4e6dd 100644
--- a/include/linux/huge_mm.h
+++ b/include/linux/huge_mm.h
@@ -123,6 +123,8 @@ enum mthp_stat_item {
MTHP_STAT_ANON_FAULT_ALLOC,
MTHP_STAT_ANON_FAULT_FALLBACK,
MTHP_STAT_ANON_FAULT_FALLBACK_CHARGE,
+ MTHP_STAT_COLLAPSE_ALLOC,
+ MTHP_STAT_COLLAPSE_ALLOC_FAILED,
MTHP_STAT_ZSWPOUT,
MTHP_STAT_SWPIN,
MTHP_STAT_SWPIN_FALLBACK,
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index d3e66136e41a..177f0a78666a 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -615,6 +615,8 @@ static struct kobj_attribute _name##_attr = __ATTR_RO(_name)
DEFINE_MTHP_STAT_ATTR(anon_fault_alloc, MTHP_STAT_ANON_FAULT_ALLOC);
DEFINE_MTHP_STAT_ATTR(anon_fault_fallback, MTHP_STAT_ANON_FAULT_FALLBACK);
DEFINE_MTHP_STAT_ATTR(anon_fault_fallback_charge, MTHP_STAT_ANON_FAULT_FALLBACK_CHARGE);
+DEFINE_MTHP_STAT_ATTR(collapse_alloc, MTHP_STAT_COLLAPSE_ALLOC);
+DEFINE_MTHP_STAT_ATTR(collapse_alloc_failed, MTHP_STAT_COLLAPSE_ALLOC_FAILED);
DEFINE_MTHP_STAT_ATTR(zswpout, MTHP_STAT_ZSWPOUT);
DEFINE_MTHP_STAT_ATTR(swpin, MTHP_STAT_SWPIN);
DEFINE_MTHP_STAT_ATTR(swpin_fallback, MTHP_STAT_SWPIN_FALLBACK);
@@ -680,6 +682,8 @@ static struct attribute *any_stats_attrs[] = {
#endif
&split_attr.attr,
&split_failed_attr.attr,
+ &collapse_alloc_attr.attr,
+ &collapse_alloc_failed_attr.attr,
NULL,
};
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 0c4d6a02d59c..cf94ccdfe751 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -1074,21 +1074,26 @@ static int __collapse_huge_page_swapin(struct mm_struct *mm,
}
static int alloc_charge_folio(struct folio **foliop, struct mm_struct *mm,
- struct collapse_control *cc)
+ struct collapse_control *cc, u8 order)
{
gfp_t gfp = (cc->is_khugepaged ? alloc_hugepage_khugepaged_gfpmask() :
GFP_TRANSHUGE);
int node = khugepaged_find_target_node(cc);
struct folio *folio;
- folio = __folio_alloc(gfp, HPAGE_PMD_ORDER, node, &cc->alloc_nmask);
+ folio = __folio_alloc(gfp, order, node, &cc->alloc_nmask);
if (!folio) {
*foliop = NULL;
- count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
+ if (order == HPAGE_PMD_ORDER)
+ count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
+ count_mthp_stat(order, MTHP_STAT_COLLAPSE_ALLOC_FAILED);
return SCAN_ALLOC_HUGE_PAGE_FAIL;
}
- count_vm_event(THP_COLLAPSE_ALLOC);
+ if (order == HPAGE_PMD_ORDER)
+ count_vm_event(THP_COLLAPSE_ALLOC);
+ count_mthp_stat(order, MTHP_STAT_COLLAPSE_ALLOC);
+
if (unlikely(mem_cgroup_charge(folio, mm, gfp))) {
folio_put(folio);
*foliop = NULL;
@@ -1125,7 +1130,7 @@ static int collapse_huge_page(struct mm_struct *mm, unsigned long address,
*/
mmap_read_unlock(mm);
- result = alloc_charge_folio(&folio, mm, cc);
+ result = alloc_charge_folio(&folio, mm, cc, HPAGE_PMD_ORDER);
if (result != SCAN_SUCCEED)
goto out_nolock;
@@ -1847,7 +1852,7 @@ static int collapse_file(struct mm_struct *mm, unsigned long addr,
VM_BUG_ON(!IS_ENABLED(CONFIG_READ_ONLY_THP_FOR_FS) && !is_shmem);
VM_BUG_ON(start & (HPAGE_PMD_NR - 1));
- result = alloc_charge_folio(&new_folio, mm, cc);
+ result = alloc_charge_folio(&new_folio, mm, cc, HPAGE_PMD_ORDER);
if (result != SCAN_SUCCEED)
goto out;
--
2.49.0
^ permalink raw reply related [flat|nested] 16+ messages in thread
* [PATCH v6 05/12] khugepaged: generalize __collapse_huge_page_* for mTHP support
2025-05-15 3:03 ` [PATCH v6 04/12] khugepaged: generalize alloc_charge_folio() Nico Pache
@ 2025-05-15 3:03 ` Nico Pache
2025-05-15 3:03 ` [PATCH v6 06/12] khugepaged: introduce khugepaged_scan_bitmap " Nico Pache
0 siblings, 1 reply; 16+ messages in thread
From: Nico Pache @ 2025-05-15 3:03 UTC (permalink / raw)
To: linux-mm, linux-doc, linux-kernel, linux-trace-kernel
Cc: david, ziy, baolin.wang, lorenzo.stoakes, Liam.Howlett,
ryan.roberts, dev.jain, corbet, rostedt, mhiramat,
mathieu.desnoyers, akpm, baohua, willy, peterx, wangkefeng.wang,
usamaarif642, sunnanyong, vishal.moola, thomas.hellstrom, yang,
kirill.shutemov, aarcange, raquini, anshuman.khandual,
catalin.marinas, tiwai, will, dave.hansen, jack, cl, jglisse,
surenb, zokeefe, hannes, rientjes, mhocko, rdunlap
generalize the order of the __collapse_huge_page_* functions
to support future mTHP collapse.
mTHP collapse can suffer from incosistant behavior, and memory waste
"creep". disable swapin and shared support for mTHP collapse.
No functional changes in this patch.
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
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>
---
mm/khugepaged.c | 48 ++++++++++++++++++++++++++++++------------------
1 file changed, 30 insertions(+), 18 deletions(-)
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index cf94ccdfe751..2af8f50855d4 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -565,15 +565,17 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
unsigned long address,
pte_t *pte,
struct collapse_control *cc,
- struct list_head *compound_pagelist)
+ struct list_head *compound_pagelist,
+ u8 order)
{
struct page *page = NULL;
struct folio *folio = NULL;
pte_t *_pte;
int none_or_zero = 0, shared = 0, result = SCAN_FAIL, referenced = 0;
bool writable = false;
+ int scaled_none = khugepaged_max_ptes_none >> (HPAGE_PMD_ORDER - order);
- for (_pte = pte; _pte < pte + HPAGE_PMD_NR;
+ for (_pte = pte; _pte < pte + (1 << order);
_pte++, address += PAGE_SIZE) {
pte_t pteval = ptep_get(_pte);
if (pte_none(pteval) || (pte_present(pteval) &&
@@ -581,7 +583,7 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
++none_or_zero;
if (!userfaultfd_armed(vma) &&
(!cc->is_khugepaged ||
- none_or_zero <= khugepaged_max_ptes_none)) {
+ none_or_zero <= scaled_none)) {
continue;
} else {
result = SCAN_EXCEED_NONE_PTE;
@@ -609,8 +611,8 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
/* See hpage_collapse_scan_pmd(). */
if (folio_maybe_mapped_shared(folio)) {
++shared;
- if (cc->is_khugepaged &&
- shared > khugepaged_max_ptes_shared) {
+ if (order != HPAGE_PMD_ORDER || (cc->is_khugepaged &&
+ shared > khugepaged_max_ptes_shared)) {
result = SCAN_EXCEED_SHARED_PTE;
count_vm_event(THP_SCAN_EXCEED_SHARED_PTE);
goto out;
@@ -711,13 +713,14 @@ static void __collapse_huge_page_copy_succeeded(pte_t *pte,
struct vm_area_struct *vma,
unsigned long address,
spinlock_t *ptl,
- struct list_head *compound_pagelist)
+ struct list_head *compound_pagelist,
+ u8 order)
{
struct folio *src, *tmp;
pte_t *_pte;
pte_t pteval;
- for (_pte = pte; _pte < pte + HPAGE_PMD_NR;
+ for (_pte = pte; _pte < pte + (1 << order);
_pte++, address += PAGE_SIZE) {
pteval = ptep_get(_pte);
if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) {
@@ -764,7 +767,8 @@ static void __collapse_huge_page_copy_failed(pte_t *pte,
pmd_t *pmd,
pmd_t orig_pmd,
struct vm_area_struct *vma,
- struct list_head *compound_pagelist)
+ struct list_head *compound_pagelist,
+ u8 order)
{
spinlock_t *pmd_ptl;
@@ -781,7 +785,7 @@ static void __collapse_huge_page_copy_failed(pte_t *pte,
* Release both raw and compound pages isolated
* in __collapse_huge_page_isolate.
*/
- release_pte_pages(pte, pte + HPAGE_PMD_NR, compound_pagelist);
+ release_pte_pages(pte, pte + (1 << order), compound_pagelist);
}
/*
@@ -802,7 +806,7 @@ static void __collapse_huge_page_copy_failed(pte_t *pte,
static int __collapse_huge_page_copy(pte_t *pte, struct folio *folio,
pmd_t *pmd, pmd_t orig_pmd, struct vm_area_struct *vma,
unsigned long address, spinlock_t *ptl,
- struct list_head *compound_pagelist)
+ struct list_head *compound_pagelist, u8 order)
{
unsigned int i;
int result = SCAN_SUCCEED;
@@ -810,7 +814,7 @@ static int __collapse_huge_page_copy(pte_t *pte, struct folio *folio,
/*
* Copying pages' contents is subject to memory poison at any iteration.
*/
- for (i = 0; i < HPAGE_PMD_NR; i++) {
+ for (i = 0; i < (1 << order); i++) {
pte_t pteval = ptep_get(pte + i);
struct page *page = folio_page(folio, i);
unsigned long src_addr = address + i * PAGE_SIZE;
@@ -829,10 +833,10 @@ static int __collapse_huge_page_copy(pte_t *pte, struct folio *folio,
if (likely(result == SCAN_SUCCEED))
__collapse_huge_page_copy_succeeded(pte, vma, address, ptl,
- compound_pagelist);
+ compound_pagelist, order);
else
__collapse_huge_page_copy_failed(pte, pmd, orig_pmd, vma,
- compound_pagelist);
+ compound_pagelist, order);
return result;
}
@@ -1000,11 +1004,11 @@ static int check_pmd_still_valid(struct mm_struct *mm,
static int __collapse_huge_page_swapin(struct mm_struct *mm,
struct vm_area_struct *vma,
unsigned long haddr, pmd_t *pmd,
- int referenced)
+ int referenced, u8 order)
{
int swapped_in = 0;
vm_fault_t ret = 0;
- unsigned long address, end = haddr + (HPAGE_PMD_NR * PAGE_SIZE);
+ unsigned long address, end = haddr + (PAGE_SIZE << order);
int result;
pte_t *pte = NULL;
spinlock_t *ptl;
@@ -1035,6 +1039,14 @@ static int __collapse_huge_page_swapin(struct mm_struct *mm,
if (!is_swap_pte(vmf.orig_pte))
continue;
+ /* Dont swapin for mTHP collapse */
+ if (order != HPAGE_PMD_ORDER) {
+ pte_unmap(pte);
+ mmap_read_unlock(mm);
+ result = SCAN_EXCEED_SWAP_PTE;
+ goto out;
+ }
+
vmf.pte = pte;
vmf.ptl = ptl;
ret = do_swap_page(&vmf);
@@ -1154,7 +1166,7 @@ static int collapse_huge_page(struct mm_struct *mm, unsigned long address,
* that case. Continuing to collapse causes inconsistency.
*/
result = __collapse_huge_page_swapin(mm, vma, address, pmd,
- referenced);
+ referenced, HPAGE_PMD_ORDER);
if (result != SCAN_SUCCEED)
goto out_nolock;
}
@@ -1201,7 +1213,7 @@ static int collapse_huge_page(struct mm_struct *mm, unsigned long address,
pte = pte_offset_map_lock(mm, &_pmd, address, &pte_ptl);
if (pte) {
result = __collapse_huge_page_isolate(vma, address, pte, cc,
- &compound_pagelist);
+ &compound_pagelist, HPAGE_PMD_ORDER);
spin_unlock(pte_ptl);
} else {
result = SCAN_PMD_NULL;
@@ -1231,7 +1243,7 @@ static int collapse_huge_page(struct mm_struct *mm, unsigned long address,
result = __collapse_huge_page_copy(pte, folio, pmd, _pmd,
vma, address, pte_ptl,
- &compound_pagelist);
+ &compound_pagelist, HPAGE_PMD_ORDER);
pte_unmap(pte);
if (unlikely(result != SCAN_SUCCEED))
goto out_up_write;
--
2.49.0
^ permalink raw reply related [flat|nested] 16+ messages in thread
* [PATCH v6 06/12] khugepaged: introduce khugepaged_scan_bitmap for mTHP support
2025-05-15 3:03 ` [PATCH v6 05/12] khugepaged: generalize __collapse_huge_page_* for mTHP support Nico Pache
@ 2025-05-15 3:03 ` Nico Pache
2025-05-15 3:03 ` [PATCH v6 07/12] khugepaged: add " Nico Pache
0 siblings, 1 reply; 16+ messages in thread
From: Nico Pache @ 2025-05-15 3:03 UTC (permalink / raw)
To: linux-mm, linux-doc, linux-kernel, linux-trace-kernel
Cc: david, ziy, baolin.wang, lorenzo.stoakes, Liam.Howlett,
ryan.roberts, dev.jain, corbet, rostedt, mhiramat,
mathieu.desnoyers, akpm, baohua, willy, peterx, wangkefeng.wang,
usamaarif642, sunnanyong, vishal.moola, thomas.hellstrom, yang,
kirill.shutemov, aarcange, raquini, anshuman.khandual,
catalin.marinas, tiwai, will, dave.hansen, jack, cl, jglisse,
surenb, zokeefe, hannes, rientjes, mhocko, rdunlap
khugepaged scans anons PMD ranges for potential collapse to a hugepage.
To add mTHP support we use this scan to instead record chunks of utilized
sections of the PMD.
khugepaged_scan_bitmap uses a stack struct to recursively scan a bitmap
that represents chunks of utilized regions. We can then determine what
mTHP size fits best and in the following patch, we set this bitmap while
scanning the anon PMD. A minimum collapse order of 2 is used as this is
the lowest order supported by anon memory.
max_ptes_none is used as a scale to determine how "full" an order must
be before being considered for collapse.
When attempting to collapse an order that has its order set to "always"
lets always collapse to that order in a greedy manner without
considering the number of bits set.
Signed-off-by: Nico Pache <npache@redhat.com>
---
include/linux/khugepaged.h | 4 ++
mm/khugepaged.c | 94 ++++++++++++++++++++++++++++++++++----
2 files changed, 89 insertions(+), 9 deletions(-)
diff --git a/include/linux/khugepaged.h b/include/linux/khugepaged.h
index b8d69cfbb58b..b6e5ba1fae58 100644
--- a/include/linux/khugepaged.h
+++ b/include/linux/khugepaged.h
@@ -1,6 +1,10 @@
/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _LINUX_KHUGEPAGED_H
#define _LINUX_KHUGEPAGED_H
+#define KHUGEPAGED_MIN_MTHP_ORDER 2
+#define KHUGEPAGED_MIN_MTHP_NR (1<<KHUGEPAGED_MIN_MTHP_ORDER)
+#define MAX_MTHP_BITMAP_SIZE (1 << (ilog2(MAX_PTRS_PER_PTE) - KHUGEPAGED_MIN_MTHP_ORDER))
+#define MTHP_BITMAP_SIZE (1 << (HPAGE_PMD_ORDER - KHUGEPAGED_MIN_MTHP_ORDER))
extern unsigned int khugepaged_max_ptes_none __read_mostly;
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 2af8f50855d4..044fec869b50 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -94,6 +94,11 @@ static DEFINE_READ_MOSTLY_HASHTABLE(mm_slots_hash, MM_SLOTS_HASH_BITS);
static struct kmem_cache *mm_slot_cache __ro_after_init;
+struct scan_bit_state {
+ u8 order;
+ u16 offset;
+};
+
struct collapse_control {
bool is_khugepaged;
@@ -102,6 +107,18 @@ struct collapse_control {
/* nodemask for allocation fallback */
nodemask_t alloc_nmask;
+
+ /*
+ * bitmap used to collapse mTHP sizes.
+ * 1bit = order KHUGEPAGED_MIN_MTHP_ORDER mTHP
+ */
+ DECLARE_BITMAP(mthp_bitmap, MAX_MTHP_BITMAP_SIZE);
+ DECLARE_BITMAP(mthp_bitmap_temp, MAX_MTHP_BITMAP_SIZE);
+ struct scan_bit_state mthp_bitmap_stack[MAX_MTHP_BITMAP_SIZE];
+};
+
+struct collapse_control khugepaged_collapse_control = {
+ .is_khugepaged = true,
};
/**
@@ -851,10 +868,6 @@ static void khugepaged_alloc_sleep(void)
remove_wait_queue(&khugepaged_wait, &wait);
}
-struct collapse_control khugepaged_collapse_control = {
- .is_khugepaged = true,
-};
-
static bool khugepaged_scan_abort(int nid, struct collapse_control *cc)
{
int i;
@@ -1120,7 +1133,8 @@ static int alloc_charge_folio(struct folio **foliop, struct mm_struct *mm,
static int collapse_huge_page(struct mm_struct *mm, unsigned long address,
int referenced, int unmapped,
- struct collapse_control *cc)
+ struct collapse_control *cc, bool *mmap_locked,
+ u8 order, u16 offset)
{
LIST_HEAD(compound_pagelist);
pmd_t *pmd, _pmd;
@@ -1139,8 +1153,12 @@ static int collapse_huge_page(struct mm_struct *mm, unsigned long address,
* The allocation can take potentially a long time if it involves
* sync compaction, and we do not need to hold the mmap_lock during
* that. We will recheck the vma after taking it again in write mode.
+ * If collapsing mTHPs we may have already released the read_lock.
*/
- mmap_read_unlock(mm);
+ if (*mmap_locked) {
+ mmap_read_unlock(mm);
+ *mmap_locked = false;
+ }
result = alloc_charge_folio(&folio, mm, cc, HPAGE_PMD_ORDER);
if (result != SCAN_SUCCEED)
@@ -1275,12 +1293,72 @@ static int collapse_huge_page(struct mm_struct *mm, unsigned long address,
out_up_write:
mmap_write_unlock(mm);
out_nolock:
+ *mmap_locked = false;
if (folio)
folio_put(folio);
trace_mm_collapse_huge_page(mm, result == SCAN_SUCCEED, result);
return result;
}
+/* Recursive function to consume the bitmap */
+static int khugepaged_scan_bitmap(struct mm_struct *mm, unsigned long address,
+ int referenced, int unmapped, struct collapse_control *cc,
+ bool *mmap_locked, unsigned long enabled_orders)
+{
+ u8 order, next_order;
+ u16 offset, mid_offset;
+ int num_chunks;
+ int bits_set, threshold_bits;
+ int top = -1;
+ int collapsed = 0;
+ int ret;
+ struct scan_bit_state state;
+ bool is_pmd_only = (enabled_orders == (1 << HPAGE_PMD_ORDER));
+
+ cc->mthp_bitmap_stack[++top] = (struct scan_bit_state)
+ { HPAGE_PMD_ORDER - KHUGEPAGED_MIN_MTHP_ORDER, 0 };
+
+ while (top >= 0) {
+ state = cc->mthp_bitmap_stack[top--];
+ order = state.order + KHUGEPAGED_MIN_MTHP_ORDER;
+ offset = state.offset;
+ num_chunks = 1 << (state.order);
+ // Skip mTHP orders that are not enabled
+ if (!test_bit(order, &enabled_orders))
+ goto next;
+
+ // copy the relavant section to a new bitmap
+ bitmap_shift_right(cc->mthp_bitmap_temp, cc->mthp_bitmap, offset,
+ MTHP_BITMAP_SIZE);
+
+ bits_set = bitmap_weight(cc->mthp_bitmap_temp, num_chunks);
+ threshold_bits = (HPAGE_PMD_NR - khugepaged_max_ptes_none - 1)
+ >> (HPAGE_PMD_ORDER - state.order);
+
+ //Check if the region is "almost full" based on the threshold
+ if (bits_set > threshold_bits || is_pmd_only
+ || test_bit(order, &huge_anon_orders_always)) {
+ ret = collapse_huge_page(mm, address, referenced, unmapped, cc,
+ mmap_locked, order, offset * KHUGEPAGED_MIN_MTHP_NR);
+ if (ret == SCAN_SUCCEED) {
+ collapsed += (1 << order);
+ continue;
+ }
+ }
+
+next:
+ if (state.order > 0) {
+ next_order = state.order - 1;
+ mid_offset = offset + (num_chunks / 2);
+ cc->mthp_bitmap_stack[++top] = (struct scan_bit_state)
+ { next_order, mid_offset };
+ cc->mthp_bitmap_stack[++top] = (struct scan_bit_state)
+ { next_order, offset };
+ }
+ }
+ return collapsed;
+}
+
static int khugepaged_scan_pmd(struct mm_struct *mm,
struct vm_area_struct *vma,
unsigned long address, bool *mmap_locked,
@@ -1447,9 +1525,7 @@ static int khugepaged_scan_pmd(struct mm_struct *mm,
pte_unmap_unlock(pte, ptl);
if (result == SCAN_SUCCEED) {
result = collapse_huge_page(mm, address, referenced,
- unmapped, cc);
- /* collapse_huge_page will return with the mmap_lock released */
- *mmap_locked = false;
+ unmapped, cc, mmap_locked, HPAGE_PMD_ORDER, 0);
}
out:
trace_mm_khugepaged_scan_pmd(mm, folio, writable, referenced,
--
2.49.0
^ permalink raw reply related [flat|nested] 16+ messages in thread
* [PATCH v6 07/12] khugepaged: add mTHP support
2025-05-15 3:03 ` [PATCH v6 06/12] khugepaged: introduce khugepaged_scan_bitmap " Nico Pache
@ 2025-05-15 3:03 ` Nico Pache
2025-05-15 3:03 ` [PATCH v6 08/12] khugepaged: skip collapsing mTHP to smaller orders Nico Pache
0 siblings, 1 reply; 16+ messages in thread
From: Nico Pache @ 2025-05-15 3:03 UTC (permalink / raw)
To: linux-mm, linux-doc, linux-kernel, linux-trace-kernel
Cc: david, ziy, baolin.wang, lorenzo.stoakes, Liam.Howlett,
ryan.roberts, dev.jain, corbet, rostedt, mhiramat,
mathieu.desnoyers, akpm, baohua, willy, peterx, wangkefeng.wang,
usamaarif642, sunnanyong, vishal.moola, thomas.hellstrom, yang,
kirill.shutemov, aarcange, raquini, anshuman.khandual,
catalin.marinas, tiwai, will, dave.hansen, jack, cl, jglisse,
surenb, zokeefe, hannes, rientjes, mhocko, rdunlap
Introduce the ability for khugepaged to collapse to different mTHP sizes.
While scanning PMD ranges for potential collapse candidates, keep track
of pages in KHUGEPAGED_MIN_MTHP_ORDER chunks via a bitmap. Each bit
represents a utilized region of order KHUGEPAGED_MIN_MTHP_ORDER ptes. If
mTHPs are enabled we remove the restriction of max_ptes_none during the
scan phase so we dont bailout early and miss potential mTHP candidates.
After the scan is complete we will perform binary recursion on the
bitmap to determine which mTHP size would be most efficient to collapse
to. max_ptes_none will be scaled by the attempted collapse order to
determine how full a THP must be to be eligible.
If a mTHP collapse is attempted, but contains swapped out, or shared
pages, we dont perform the collapse.
For non PMD collapse we much leave the anon VMA write locked until after
we collapse the mTHP
Signed-off-by: Nico Pache <npache@redhat.com>
---
mm/khugepaged.c | 136 +++++++++++++++++++++++++++++++++---------------
1 file changed, 95 insertions(+), 41 deletions(-)
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 044fec869b50..afad75fc01b7 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -1138,13 +1138,14 @@ static int collapse_huge_page(struct mm_struct *mm, unsigned long address,
{
LIST_HEAD(compound_pagelist);
pmd_t *pmd, _pmd;
- pte_t *pte;
+ pte_t *pte = NULL, mthp_pte;
pgtable_t pgtable;
struct folio *folio;
spinlock_t *pmd_ptl, *pte_ptl;
int result = SCAN_FAIL;
struct vm_area_struct *vma;
struct mmu_notifier_range range;
+ unsigned long _address = address + offset * PAGE_SIZE;
VM_BUG_ON(address & ~HPAGE_PMD_MASK);
@@ -1160,12 +1161,13 @@ static int collapse_huge_page(struct mm_struct *mm, unsigned long address,
*mmap_locked = false;
}
- result = alloc_charge_folio(&folio, mm, cc, HPAGE_PMD_ORDER);
+ result = alloc_charge_folio(&folio, mm, cc, order);
if (result != SCAN_SUCCEED)
goto out_nolock;
mmap_read_lock(mm);
- result = hugepage_vma_revalidate(mm, address, true, &vma, cc, HPAGE_PMD_ORDER);
+ *mmap_locked = true;
+ result = hugepage_vma_revalidate(mm, address, true, &vma, cc, order);
if (result != SCAN_SUCCEED) {
mmap_read_unlock(mm);
goto out_nolock;
@@ -1183,13 +1185,14 @@ static int collapse_huge_page(struct mm_struct *mm, unsigned long address,
* released when it fails. So we jump out_nolock directly in
* that case. Continuing to collapse causes inconsistency.
*/
- result = __collapse_huge_page_swapin(mm, vma, address, pmd,
- referenced, HPAGE_PMD_ORDER);
+ result = __collapse_huge_page_swapin(mm, vma, _address, pmd,
+ referenced, order);
if (result != SCAN_SUCCEED)
goto out_nolock;
}
mmap_read_unlock(mm);
+ *mmap_locked = false;
/*
* Prevent all access to pagetables with the exception of
* gup_fast later handled by the ptep_clear_flush and the VM
@@ -1199,7 +1202,7 @@ static int collapse_huge_page(struct mm_struct *mm, unsigned long address,
* mmap_lock.
*/
mmap_write_lock(mm);
- result = hugepage_vma_revalidate(mm, address, true, &vma, cc, HPAGE_PMD_ORDER);
+ result = hugepage_vma_revalidate(mm, address, true, &vma, cc, order);
if (result != SCAN_SUCCEED)
goto out_up_write;
/* check if the pmd is still valid */
@@ -1210,11 +1213,12 @@ static int collapse_huge_page(struct mm_struct *mm, unsigned long address,
vma_start_write(vma);
anon_vma_lock_write(vma->anon_vma);
- mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, mm, address,
- address + HPAGE_PMD_SIZE);
+ mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, mm, _address,
+ _address + (PAGE_SIZE << order));
mmu_notifier_invalidate_range_start(&range);
pmd_ptl = pmd_lock(mm, pmd); /* probably unnecessary */
+
/*
* This removes any huge TLB entry from the CPU so we won't allow
* huge and small TLB entries for the same virtual address to
@@ -1228,18 +1232,16 @@ static int collapse_huge_page(struct mm_struct *mm, unsigned long address,
mmu_notifier_invalidate_range_end(&range);
tlb_remove_table_sync_one();
- pte = pte_offset_map_lock(mm, &_pmd, address, &pte_ptl);
+ pte = pte_offset_map_lock(mm, &_pmd, _address, &pte_ptl);
if (pte) {
- result = __collapse_huge_page_isolate(vma, address, pte, cc,
- &compound_pagelist, HPAGE_PMD_ORDER);
+ result = __collapse_huge_page_isolate(vma, _address, pte, cc,
+ &compound_pagelist, order);
spin_unlock(pte_ptl);
} else {
result = SCAN_PMD_NULL;
}
if (unlikely(result != SCAN_SUCCEED)) {
- if (pte)
- pte_unmap(pte);
spin_lock(pmd_ptl);
BUG_ON(!pmd_none(*pmd));
/*
@@ -1254,17 +1256,17 @@ static int collapse_huge_page(struct mm_struct *mm, unsigned long address,
}
/*
- * All pages are isolated and locked so anon_vma rmap
- * can't run anymore.
+ * For PMD collapse all pages are isolated and locked so anon_vma
+ * rmap can't run anymore
*/
- anon_vma_unlock_write(vma->anon_vma);
+ if (order == HPAGE_PMD_ORDER)
+ anon_vma_unlock_write(vma->anon_vma);
result = __collapse_huge_page_copy(pte, folio, pmd, _pmd,
- vma, address, pte_ptl,
- &compound_pagelist, HPAGE_PMD_ORDER);
- pte_unmap(pte);
+ vma, _address, pte_ptl,
+ &compound_pagelist, order);
if (unlikely(result != SCAN_SUCCEED))
- goto out_up_write;
+ goto out_unlock_anon_vma;
/*
* The smp_wmb() inside __folio_mark_uptodate() ensures the
@@ -1272,25 +1274,45 @@ static int collapse_huge_page(struct mm_struct *mm, unsigned long address,
* write.
*/
__folio_mark_uptodate(folio);
- pgtable = pmd_pgtable(_pmd);
-
- _pmd = folio_mk_pmd(folio, vma->vm_page_prot);
- _pmd = maybe_pmd_mkwrite(pmd_mkdirty(_pmd), vma);
-
- spin_lock(pmd_ptl);
- BUG_ON(!pmd_none(*pmd));
- folio_add_new_anon_rmap(folio, vma, address, RMAP_EXCLUSIVE);
- folio_add_lru_vma(folio, vma);
- pgtable_trans_huge_deposit(mm, pmd, pgtable);
- set_pmd_at(mm, address, pmd, _pmd);
- update_mmu_cache_pmd(vma, address, pmd);
- deferred_split_folio(folio, false);
- spin_unlock(pmd_ptl);
+ if (order == HPAGE_PMD_ORDER) {
+ pgtable = pmd_pgtable(_pmd);
+ _pmd = folio_mk_pmd(folio, vma->vm_page_prot);
+ _pmd = maybe_pmd_mkwrite(pmd_mkdirty(_pmd), vma);
+
+ spin_lock(pmd_ptl);
+ BUG_ON(!pmd_none(*pmd));
+ folio_add_new_anon_rmap(folio, vma, _address, RMAP_EXCLUSIVE);
+ folio_add_lru_vma(folio, vma);
+ pgtable_trans_huge_deposit(mm, pmd, pgtable);
+ set_pmd_at(mm, address, pmd, _pmd);
+ update_mmu_cache_pmd(vma, address, pmd);
+ deferred_split_folio(folio, false);
+ spin_unlock(pmd_ptl);
+ } else { /* mTHP collapse */
+ mthp_pte = mk_pte(&folio->page, vma->vm_page_prot);
+ mthp_pte = maybe_mkwrite(pte_mkdirty(mthp_pte), vma);
+
+ spin_lock(pmd_ptl);
+ folio_ref_add(folio, (1 << order) - 1);
+ folio_add_new_anon_rmap(folio, vma, _address, RMAP_EXCLUSIVE);
+ folio_add_lru_vma(folio, vma);
+ set_ptes(vma->vm_mm, _address, pte, mthp_pte, (1 << order));
+ update_mmu_cache_range(NULL, vma, _address, pte, (1 << order));
+
+ smp_wmb(); /* make pte visible before pmd */
+ pmd_populate(mm, pmd, pmd_pgtable(_pmd));
+ spin_unlock(pmd_ptl);
+ }
folio = NULL;
result = SCAN_SUCCEED;
+out_unlock_anon_vma:
+ if (order != HPAGE_PMD_ORDER)
+ anon_vma_unlock_write(vma->anon_vma);
out_up_write:
+ if (pte)
+ pte_unmap(pte);
mmap_write_unlock(mm);
out_nolock:
*mmap_locked = false;
@@ -1366,31 +1388,57 @@ static int khugepaged_scan_pmd(struct mm_struct *mm,
{
pmd_t *pmd;
pte_t *pte, *_pte;
+ int i;
int result = SCAN_FAIL, referenced = 0;
int none_or_zero = 0, shared = 0;
struct page *page = NULL;
struct folio *folio = NULL;
unsigned long _address;
+ unsigned long enabled_orders;
spinlock_t *ptl;
int node = NUMA_NO_NODE, unmapped = 0;
+ bool is_pmd_only;
bool writable = false;
-
+ int chunk_none_count = 0;
+ int scaled_none = khugepaged_max_ptes_none >> (HPAGE_PMD_ORDER - KHUGEPAGED_MIN_MTHP_ORDER);
+ unsigned long tva_flags = cc->is_khugepaged ? TVA_ENFORCE_SYSFS : 0;
VM_BUG_ON(address & ~HPAGE_PMD_MASK);
result = find_pmd_or_thp_or_none(mm, address, &pmd);
if (result != SCAN_SUCCEED)
goto out;
+ bitmap_zero(cc->mthp_bitmap, MAX_MTHP_BITMAP_SIZE);
+ bitmap_zero(cc->mthp_bitmap_temp, MAX_MTHP_BITMAP_SIZE);
memset(cc->node_load, 0, sizeof(cc->node_load));
nodes_clear(cc->alloc_nmask);
+
+ enabled_orders = thp_vma_allowable_orders(vma, vma->vm_flags,
+ tva_flags, THP_ORDERS_ALL_ANON);
+
+ is_pmd_only = (enabled_orders == (1 << HPAGE_PMD_ORDER));
+
pte = pte_offset_map_lock(mm, pmd, address, &ptl);
if (!pte) {
result = SCAN_PMD_NULL;
goto out;
}
- for (_address = address, _pte = pte; _pte < pte + HPAGE_PMD_NR;
- _pte++, _address += PAGE_SIZE) {
+ for (i = 0; i < HPAGE_PMD_NR; i++) {
+ /*
+ * we are reading in KHUGEPAGED_MIN_MTHP_NR page chunks. if
+ * there are pages in this chunk keep track of it in the bitmap
+ * for mTHP collapsing.
+ */
+ if (i % KHUGEPAGED_MIN_MTHP_NR == 0) {
+ if (chunk_none_count <= scaled_none)
+ bitmap_set(cc->mthp_bitmap,
+ i / KHUGEPAGED_MIN_MTHP_NR, 1);
+ chunk_none_count = 0;
+ }
+
+ _pte = pte + i;
+ _address = address + i * PAGE_SIZE;
pte_t pteval = ptep_get(_pte);
if (is_swap_pte(pteval)) {
++unmapped;
@@ -1413,10 +1461,11 @@ static int khugepaged_scan_pmd(struct mm_struct *mm,
}
}
if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) {
+ ++chunk_none_count;
++none_or_zero;
if (!userfaultfd_armed(vma) &&
- (!cc->is_khugepaged ||
- none_or_zero <= khugepaged_max_ptes_none)) {
+ (!cc->is_khugepaged || !is_pmd_only ||
+ none_or_zero <= khugepaged_max_ptes_none)) {
continue;
} else {
result = SCAN_EXCEED_NONE_PTE;
@@ -1512,6 +1561,7 @@ static int khugepaged_scan_pmd(struct mm_struct *mm,
address)))
referenced++;
}
+
if (!writable) {
result = SCAN_PAGE_RO;
} else if (cc->is_khugepaged &&
@@ -1524,8 +1574,12 @@ static int khugepaged_scan_pmd(struct mm_struct *mm,
out_unmap:
pte_unmap_unlock(pte, ptl);
if (result == SCAN_SUCCEED) {
- result = collapse_huge_page(mm, address, referenced,
- unmapped, cc, mmap_locked, HPAGE_PMD_ORDER, 0);
+ result = khugepaged_scan_bitmap(mm, address, referenced, unmapped, cc,
+ mmap_locked, enabled_orders);
+ if (result > 0)
+ result = SCAN_SUCCEED;
+ else
+ result = SCAN_FAIL;
}
out:
trace_mm_khugepaged_scan_pmd(mm, folio, writable, referenced,
--
2.49.0
^ permalink raw reply related [flat|nested] 16+ messages in thread
* [PATCH v6 08/12] khugepaged: skip collapsing mTHP to smaller orders
2025-05-15 3:03 ` [PATCH v6 07/12] khugepaged: add " Nico Pache
@ 2025-05-15 3:03 ` Nico Pache
2025-05-15 3:03 ` [PATCH v6 09/12] khugepaged: avoid unnecessary mTHP collapse attempts Nico Pache
0 siblings, 1 reply; 16+ messages in thread
From: Nico Pache @ 2025-05-15 3:03 UTC (permalink / raw)
To: linux-mm, linux-doc, linux-kernel, linux-trace-kernel
Cc: david, ziy, baolin.wang, lorenzo.stoakes, Liam.Howlett,
ryan.roberts, dev.jain, corbet, rostedt, mhiramat,
mathieu.desnoyers, akpm, baohua, willy, peterx, wangkefeng.wang,
usamaarif642, sunnanyong, vishal.moola, thomas.hellstrom, yang,
kirill.shutemov, aarcange, raquini, anshuman.khandual,
catalin.marinas, tiwai, will, dave.hansen, jack, cl, jglisse,
surenb, zokeefe, hannes, rientjes, mhocko, rdunlap
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 patch is inspired by Dev Jain's work on khugepaged mTHP support [1].
[1] https://lore.kernel.org/lkml/20241216165105.56185-11-dev.jain@arm.com/
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
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>
---
mm/khugepaged.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index afad75fc01b7..5920d4715a11 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -625,7 +625,12 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
folio = page_folio(page);
VM_BUG_ON_FOLIO(!folio_test_anon(folio), folio);
- /* See hpage_collapse_scan_pmd(). */
+ if (order != HPAGE_PMD_ORDER && folio_order(folio) >= order) {
+ result = SCAN_PTE_MAPPED_HUGEPAGE;
+ goto out;
+ }
+
+ /* See khugepaged_scan_pmd(). */
if (folio_maybe_mapped_shared(folio)) {
++shared;
if (order != HPAGE_PMD_ORDER || (cc->is_khugepaged &&
--
2.49.0
^ permalink raw reply related [flat|nested] 16+ messages in thread
* [PATCH v6 09/12] khugepaged: avoid unnecessary mTHP collapse attempts
2025-05-15 3:03 ` [PATCH v6 08/12] khugepaged: skip collapsing mTHP to smaller orders Nico Pache
@ 2025-05-15 3:03 ` Nico Pache
2025-05-15 3:03 ` [PATCH v6 10/12] khugepaged: improve tracepoints for mTHP orders Nico Pache
0 siblings, 1 reply; 16+ messages in thread
From: Nico Pache @ 2025-05-15 3:03 UTC (permalink / raw)
To: linux-mm, linux-doc, linux-kernel, linux-trace-kernel
Cc: david, ziy, baolin.wang, lorenzo.stoakes, Liam.Howlett,
ryan.roberts, dev.jain, corbet, rostedt, mhiramat,
mathieu.desnoyers, akpm, baohua, willy, peterx, wangkefeng.wang,
usamaarif642, sunnanyong, vishal.moola, thomas.hellstrom, yang,
kirill.shutemov, aarcange, raquini, anshuman.khandual,
catalin.marinas, tiwai, will, dave.hansen, jack, cl, jglisse,
surenb, zokeefe, hannes, rientjes, mhocko, rdunlap
There are cases where, if an attempted collapse fails, all subsequent
orders are guaranteed to also fail. Avoid these collapse attempts by
bailing out early.
Signed-off-by: Nico Pache <npache@redhat.com>
---
mm/khugepaged.c | 17 +++++++++++++++++
1 file changed, 17 insertions(+)
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 5920d4715a11..517cf2b271d7 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -1371,6 +1371,23 @@ static int khugepaged_scan_bitmap(struct mm_struct *mm, unsigned long address,
collapsed += (1 << order);
continue;
}
+ /*
+ * Some ret values indicate all lower order will also
+ * fail, dont trying to collapse smaller orders
+ */
+ if (ret == SCAN_EXCEED_NONE_PTE ||
+ ret == SCAN_EXCEED_SWAP_PTE ||
+ ret == SCAN_EXCEED_SHARED_PTE ||
+ ret == SCAN_PTE_NON_PRESENT ||
+ ret == SCAN_PTE_UFFD_WP ||
+ ret == SCAN_ALLOC_HUGE_PAGE_FAIL ||
+ ret == SCAN_CGROUP_CHARGE_FAIL ||
+ ret == SCAN_COPY_MC ||
+ ret == SCAN_PAGE_LOCK ||
+ ret == SCAN_PAGE_COUNT)
+ goto next;
+ else
+ break;
}
next:
--
2.49.0
^ permalink raw reply related [flat|nested] 16+ messages in thread
* [PATCH v6 10/12] khugepaged: improve tracepoints for mTHP orders
2025-05-15 3:03 ` [PATCH v6 09/12] khugepaged: avoid unnecessary mTHP collapse attempts Nico Pache
@ 2025-05-15 3:03 ` Nico Pache
2025-05-15 3:03 ` [PATCH v6 11/12] khugepaged: add per-order mTHP khugepaged stats Nico Pache
0 siblings, 1 reply; 16+ messages in thread
From: Nico Pache @ 2025-05-15 3:03 UTC (permalink / raw)
To: linux-mm, linux-doc, linux-kernel, linux-trace-kernel
Cc: david, ziy, baolin.wang, lorenzo.stoakes, Liam.Howlett,
ryan.roberts, dev.jain, corbet, rostedt, mhiramat,
mathieu.desnoyers, akpm, baohua, willy, peterx, wangkefeng.wang,
usamaarif642, sunnanyong, vishal.moola, thomas.hellstrom, yang,
kirill.shutemov, aarcange, raquini, anshuman.khandual,
catalin.marinas, tiwai, will, dave.hansen, jack, cl, jglisse,
surenb, zokeefe, hannes, rientjes, mhocko, rdunlap
Add the order to the tracepoints to give better insight into what order
is being operated at for khugepaged.
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Signed-off-by: Nico Pache <npache@redhat.com>
---
include/trace/events/huge_memory.h | 34 +++++++++++++++++++-----------
mm/khugepaged.c | 10 +++++----
2 files changed, 28 insertions(+), 16 deletions(-)
diff --git a/include/trace/events/huge_memory.h b/include/trace/events/huge_memory.h
index 2305df6cb485..70661bbf676f 100644
--- a/include/trace/events/huge_memory.h
+++ b/include/trace/events/huge_memory.h
@@ -92,34 +92,37 @@ TRACE_EVENT(mm_khugepaged_scan_pmd,
TRACE_EVENT(mm_collapse_huge_page,
- TP_PROTO(struct mm_struct *mm, int isolated, int status),
+ TP_PROTO(struct mm_struct *mm, int isolated, int status, int order),
- TP_ARGS(mm, isolated, status),
+ TP_ARGS(mm, isolated, status, order),
TP_STRUCT__entry(
__field(struct mm_struct *, mm)
__field(int, isolated)
__field(int, status)
+ __field(int, order)
),
TP_fast_assign(
__entry->mm = mm;
__entry->isolated = isolated;
__entry->status = status;
+ __entry->order = order;
),
- TP_printk("mm=%p, isolated=%d, status=%s",
+ TP_printk("mm=%p, isolated=%d, status=%s order=%d",
__entry->mm,
__entry->isolated,
- __print_symbolic(__entry->status, SCAN_STATUS))
+ __print_symbolic(__entry->status, SCAN_STATUS),
+ __entry->order)
);
TRACE_EVENT(mm_collapse_huge_page_isolate,
TP_PROTO(struct folio *folio, int none_or_zero,
- int referenced, bool writable, int status),
+ int referenced, bool writable, int status, int order),
- TP_ARGS(folio, none_or_zero, referenced, writable, status),
+ TP_ARGS(folio, none_or_zero, referenced, writable, status, order),
TP_STRUCT__entry(
__field(unsigned long, pfn)
@@ -127,6 +130,7 @@ TRACE_EVENT(mm_collapse_huge_page_isolate,
__field(int, referenced)
__field(bool, writable)
__field(int, status)
+ __field(int, order)
),
TP_fast_assign(
@@ -135,27 +139,31 @@ TRACE_EVENT(mm_collapse_huge_page_isolate,
__entry->referenced = referenced;
__entry->writable = writable;
__entry->status = status;
+ __entry->order = order;
),
- TP_printk("scan_pfn=0x%lx, none_or_zero=%d, referenced=%d, writable=%d, status=%s",
+ TP_printk("scan_pfn=0x%lx, none_or_zero=%d, referenced=%d, writable=%d, status=%s order=%d",
__entry->pfn,
__entry->none_or_zero,
__entry->referenced,
__entry->writable,
- __print_symbolic(__entry->status, SCAN_STATUS))
+ __print_symbolic(__entry->status, SCAN_STATUS),
+ __entry->order)
);
TRACE_EVENT(mm_collapse_huge_page_swapin,
- TP_PROTO(struct mm_struct *mm, int swapped_in, int referenced, int ret),
+ TP_PROTO(struct mm_struct *mm, int swapped_in, int referenced, int ret,
+ int order),
- TP_ARGS(mm, swapped_in, referenced, ret),
+ TP_ARGS(mm, swapped_in, referenced, ret, order),
TP_STRUCT__entry(
__field(struct mm_struct *, mm)
__field(int, swapped_in)
__field(int, referenced)
__field(int, ret)
+ __field(int, order)
),
TP_fast_assign(
@@ -163,13 +171,15 @@ TRACE_EVENT(mm_collapse_huge_page_swapin,
__entry->swapped_in = swapped_in;
__entry->referenced = referenced;
__entry->ret = ret;
+ __entry->order = order;
),
- TP_printk("mm=%p, swapped_in=%d, referenced=%d, ret=%d",
+ TP_printk("mm=%p, swapped_in=%d, referenced=%d, ret=%d, order=%d",
__entry->mm,
__entry->swapped_in,
__entry->referenced,
- __entry->ret)
+ __entry->ret,
+ __entry->order)
);
TRACE_EVENT(mm_khugepaged_scan_file,
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 517cf2b271d7..951c44778f56 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -721,13 +721,14 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
} else {
result = SCAN_SUCCEED;
trace_mm_collapse_huge_page_isolate(folio, none_or_zero,
- referenced, writable, result);
+ referenced, writable, result,
+ order);
return result;
}
out:
release_pte_pages(pte, _pte, compound_pagelist);
trace_mm_collapse_huge_page_isolate(folio, none_or_zero,
- referenced, writable, result);
+ referenced, writable, result, order);
return result;
}
@@ -1099,7 +1100,8 @@ static int __collapse_huge_page_swapin(struct mm_struct *mm,
result = SCAN_SUCCEED;
out:
- trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, result);
+ trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, result,
+ order);
return result;
}
@@ -1323,7 +1325,7 @@ static int collapse_huge_page(struct mm_struct *mm, unsigned long address,
*mmap_locked = false;
if (folio)
folio_put(folio);
- trace_mm_collapse_huge_page(mm, result == SCAN_SUCCEED, result);
+ trace_mm_collapse_huge_page(mm, result == SCAN_SUCCEED, result, order);
return result;
}
--
2.49.0
^ permalink raw reply related [flat|nested] 16+ messages in thread
* [PATCH v6 11/12] khugepaged: add per-order mTHP khugepaged stats
2025-05-15 3:03 ` [PATCH v6 10/12] khugepaged: improve tracepoints for mTHP orders Nico Pache
@ 2025-05-15 3:03 ` Nico Pache
2025-05-15 3:03 ` [PATCH v6 12/12] Documentation: mm: update the admin guide for mTHP collapse Nico Pache
0 siblings, 1 reply; 16+ messages in thread
From: Nico Pache @ 2025-05-15 3:03 UTC (permalink / raw)
To: linux-mm, linux-doc, linux-kernel, linux-trace-kernel
Cc: david, ziy, baolin.wang, lorenzo.stoakes, Liam.Howlett,
ryan.roberts, dev.jain, corbet, rostedt, mhiramat,
mathieu.desnoyers, akpm, baohua, willy, peterx, wangkefeng.wang,
usamaarif642, sunnanyong, vishal.moola, thomas.hellstrom, yang,
kirill.shutemov, aarcange, raquini, anshuman.khandual,
catalin.marinas, tiwai, will, dave.hansen, jack, cl, jglisse,
surenb, zokeefe, hannes, rientjes, mhocko, rdunlap
With mTHP support inplace, let add the per-order mTHP stats for
exceeding NONE, SWAP, and SHARED.
Signed-off-by: Nico Pache <npache@redhat.com>
---
include/linux/huge_mm.h | 3 +++
mm/huge_memory.c | 7 +++++++
mm/khugepaged.c | 15 ++++++++++++---
3 files changed, 22 insertions(+), 3 deletions(-)
diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
index 0bb65bd4e6dd..e3d15c737008 100644
--- a/include/linux/huge_mm.h
+++ b/include/linux/huge_mm.h
@@ -139,6 +139,9 @@ 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 177f0a78666a..700988a0d5cf 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -633,6 +633,10 @@ 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,
@@ -649,6 +653,9 @@ 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 951c44778f56..0723b184c7a4 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -604,7 +604,10 @@ 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;
}
}
@@ -633,8 +636,14 @@ 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;
--
2.49.0
^ permalink raw reply related [flat|nested] 16+ messages in thread
* [PATCH v6 12/12] Documentation: mm: update the admin guide for mTHP collapse
2025-05-15 3:03 ` [PATCH v6 11/12] khugepaged: add per-order mTHP khugepaged stats Nico Pache
@ 2025-05-15 3:03 ` Nico Pache
0 siblings, 0 replies; 16+ messages in thread
From: Nico Pache @ 2025-05-15 3:03 UTC (permalink / raw)
To: linux-mm, linux-doc, linux-kernel, linux-trace-kernel
Cc: david, ziy, baolin.wang, lorenzo.stoakes, Liam.Howlett,
ryan.roberts, dev.jain, corbet, rostedt, mhiramat,
mathieu.desnoyers, akpm, baohua, willy, peterx, wangkefeng.wang,
usamaarif642, sunnanyong, vishal.moola, thomas.hellstrom, yang,
kirill.shutemov, aarcange, raquini, anshuman.khandual,
catalin.marinas, tiwai, will, dave.hansen, jack, cl, jglisse,
surenb, zokeefe, hannes, rientjes, mhocko, rdunlap, Bagas Sanjaya
Now that we can collapse to mTHPs lets update the admin guide to
reflect these changes and provide proper guidence on how to utilize it.
Reviewed-by: Bagas Sanjaya <bagasdotme@gmail.com>
Signed-off-by: Nico Pache <npache@redhat.com>
---
Documentation/admin-guide/mm/transhuge.rst | 14 +++++++++++++-
1 file changed, 13 insertions(+), 1 deletion(-)
diff --git a/Documentation/admin-guide/mm/transhuge.rst b/Documentation/admin-guide/mm/transhuge.rst
index dff8d5985f0f..5c63fe51b3ad 100644
--- a/Documentation/admin-guide/mm/transhuge.rst
+++ b/Documentation/admin-guide/mm/transhuge.rst
@@ -63,7 +63,7 @@ often.
THP can be enabled system wide or restricted to certain tasks or even
memory ranges inside task's address space. Unless THP is completely
disabled, there is ``khugepaged`` daemon that scans memory and
-collapses sequences of basic pages into PMD-sized huge pages.
+collapses sequences of basic pages into huge pages.
The THP behaviour is controlled via :ref:`sysfs <thp_sysfs>`
interface and using madvise(2) and prctl(2) system calls.
@@ -144,6 +144,18 @@ hugepage sizes have enabled="never". If enabling multiple hugepage
sizes, the kernel will select the most appropriate enabled size for a
given allocation.
+khugepaged uses max_ptes_none scaled to the order of the enabled mTHP size
+to determine collapses. When using mTHPs it's recommended to set
+max_ptes_none low-- ideally less than HPAGE_PMD_NR / 2 (255 on 4k page
+size). This will prevent undesired "creep" behavior that leads to
+continuously collapsing to a larger mTHP size; When we collapse, we are
+bringing in new non-zero pages that will, on a subsequent scan, cause the
+max_ptes_none check of the +1 order to always be satisfied. By limiting
+this to less than half the current order, we make sure we don't cause this
+feedback loop. max_ptes_shared and max_ptes_swap have no effect when
+collapsing to a mTHP, and mTHP collapse will fail on shared or swapped out
+pages.
+
It's also possible to limit defrag efforts in the VM to generate
anonymous hugepages in case they're not immediately free to madvise
regions or to never try to defrag memory and simply fallback to regular
--
2.49.0
^ permalink raw reply related [flat|nested] 16+ messages in thread
* Re: [PATCH v6 00/12] khugepaged: mTHP support
2025-05-15 3:03 [PATCH v6 00/12] khugepaged: mTHP support Nico Pache
2025-05-15 3:03 ` [PATCH v6 01/12] khugepaged: rename hpage_collapse_* to khugepaged_* Nico Pache
@ 2025-05-15 3:21 ` Nico Pache
2025-05-15 6:45 ` Dev Jain
1 sibling, 1 reply; 16+ messages in thread
From: Nico Pache @ 2025-05-15 3:21 UTC (permalink / raw)
To: linux-mm, linux-doc, linux-kernel, linux-trace-kernel
Cc: david, ziy, baolin.wang, lorenzo.stoakes, Liam.Howlett,
ryan.roberts, dev.jain, corbet, rostedt, mhiramat,
mathieu.desnoyers, akpm, baohua, willy, peterx, wangkefeng.wang,
usamaarif642, sunnanyong, vishal.moola, thomas.hellstrom, yang,
kirill.shutemov, aarcange, raquini, anshuman.khandual,
catalin.marinas, tiwai, will, dave.hansen, jack, cl, jglisse,
surenb, zokeefe, hannes, rientjes, mhocko, rdunlap
Ugh... So sorry, I forgot to turn off the chain-reply-to.
resending V7 *facepalm*
On Wed, May 14, 2025 at 9:03 PM Nico Pache <npache@redhat.com> wrote:
>
> The following series provides khugepaged and madvise collapse with the
> capability to collapse anonymous memory regions to mTHPs.
>
> To achieve this we generalize the khugepaged functions to no longer depend
> on PMD_ORDER. Then during the PMD scan, we keep track of chunks of pages
> (defined by KHUGEPAGED_MTHP_MIN_ORDER) that are utilized. This info is
> tracked using a bitmap. After the PMD scan is done, we do binary recursion
> on the bitmap to find the optimal mTHP sizes for the PMD range. The
> restriction on max_ptes_none is removed during the scan, to make sure we
> account for the whole PMD range. When no mTHP size is enabled, the legacy
> behavior of khugepaged is maintained. max_ptes_none will be scaled by the
> attempted collapse order to determine how full a THP must be to be
> eligible. If a mTHP collapse is attempted, but contains swapped out, or
> shared pages, we dont perform the collapse.
>
> With the default max_ptes_none=511, the code should keep its most of its
> original behavior. To exercise mTHP collapse we need to set
> max_ptes_none<=255. With max_ptes_none > HPAGE_PMD_NR/2 you will
> experience collapse "creep" and constantly promote mTHPs to the next
> available size. This is due the fact that it will introduce at least 2x
> the number of pages, and on a future scan will satisfy that condition once
> again.
>
> Patch 1: Refactor/rename hpage_collapse
> Patch 2: Some refactoring to combine madvise_collapse and khugepaged
> Patch 3-5: Generalize khugepaged functions for arbitrary orders
> Patch 6-9: The mTHP patches
> Patch 10-11: Tracing/stats
> Patch 12: Documentation
>
> ---------
> Testing
> ---------
> - Built for x86_64, aarch64, ppc64le, and s390x
> - selftests mm
> - I created a test script that I used to push khugepaged to its limits
> while monitoring a number of stats and tracepoints. The code is
> available here[1] (Run in legacy mode for these changes and set mthp
> sizes to inherit)
> The summary from my testings was that there was no significant
> regression noticed through this test. In some cases my changes had
> better collapse latencies, and was able to scan more pages in the same
> amount of time/work, but for the most part the results were consistent.
> - redis testing. I tested these changes along with my defer changes
> (see followup post for more details).
> - some basic testing on 64k page size.
> - lots of general use.
>
> V6 Changes:
> - Dont release the anon_vma_lock early (like in the PMD case), as not all
> pages are isolated.
> - Define the PTE as null to avoid a uninitilized condition
> - minor nits and newline cleanup
> - make sure to unmap and unlock the pte for the swapin case
> - change the revalidation to always check the PMD order (as this will make
> sure that no other VMA spans it)
>
> V5 Changes [2]:
> - switched the order of patches 1 and 2
> - fixed some edge cases on the unified madvise_collapse and khugepaged
> - Explained the "creep" some more in the docs
> - fix EXCEED_SHARED vs EXCEED_SWAP accounting issue
> - fix potential highmem issue caused by a early unmap of the PTE
>
> V4 Changes:
> - Rebased onto mm-unstable
> - small changes to Documentation
>
> V3 Changes:
> - corrected legacy behavior for khugepaged and madvise_collapse
> - added proper mTHP stat tracking
> - Minor changes to prevent a nested lock on non-split-lock arches
> - Took Devs version of alloc_charge_folio as it has the proper stats
> - Skip cases were trying to collapse to a lower order would still fail
> - Fixed cases were the bitmap was not being updated properly
> - Moved Documentation update to this series instead of the defer set
> - Minor bugs discovered during testing and review
> - Minor "nit" cleanup
>
> V2 Changes:
> - Minor bug fixes discovered during review and testing
> - removed dynamic allocations for bitmaps, and made them stack based
> - Adjusted bitmap offset from u8 to u16 to support 64k pagesize.
> - Updated trace events to include collapsing order info.
> - Scaled max_ptes_none by order rather than scaling to a 0-100 scale.
> - No longer require a chunk to be fully utilized before setting the bit.
> Use the same max_ptes_none scaling principle to achieve this.
> - Skip mTHP collapse that requires swapin or shared handling. This helps
> prevent some of the "creep" that was discovered in v1.
>
> [1] - https://gitlab.com/npache/khugepaged_mthp_test
> [2] - https://lore.kernel.org/all/20250428181218.85925-1-npache@redhat.com/
>
> Dev Jain (1):
> khugepaged: generalize alloc_charge_folio()
>
> Nico Pache (11):
> khugepaged: rename hpage_collapse_* to khugepaged_*
> introduce khugepaged_collapse_single_pmd to unify khugepaged and
> madvise_collapse
> khugepaged: generalize hugepage_vma_revalidate for mTHP support
> khugepaged: generalize __collapse_huge_page_* for mTHP support
> khugepaged: introduce khugepaged_scan_bitmap for mTHP support
> khugepaged: add mTHP support
> khugepaged: skip collapsing mTHP to smaller orders
> khugepaged: avoid unnecessary mTHP collapse attempts
> khugepaged: improve tracepoints for mTHP orders
> khugepaged: add per-order mTHP khugepaged stats
> Documentation: mm: update the admin guide for mTHP collapse
>
> Documentation/admin-guide/mm/transhuge.rst | 14 +-
> include/linux/huge_mm.h | 5 +
> include/linux/khugepaged.h | 4 +
> include/trace/events/huge_memory.h | 34 +-
> mm/huge_memory.c | 11 +
> mm/khugepaged.c | 472 ++++++++++++++-------
> 6 files changed, 382 insertions(+), 158 deletions(-)
>
> --
> 2.49.0
>
^ permalink raw reply [flat|nested] 16+ messages in thread
* Re: [PATCH v6 00/12] khugepaged: mTHP support
2025-05-15 3:21 ` [PATCH v6 00/12] khugepaged: mTHP support Nico Pache
@ 2025-05-15 6:45 ` Dev Jain
2025-05-16 11:54 ` Nico Pache
0 siblings, 1 reply; 16+ messages in thread
From: Dev Jain @ 2025-05-15 6:45 UTC (permalink / raw)
To: Nico Pache, linux-mm, linux-doc, linux-kernel, linux-trace-kernel
Cc: david, ziy, baolin.wang, lorenzo.stoakes, Liam.Howlett,
ryan.roberts, corbet, rostedt, mhiramat, mathieu.desnoyers, akpm,
baohua, willy, peterx, wangkefeng.wang, usamaarif642, sunnanyong,
vishal.moola, thomas.hellstrom, yang, kirill.shutemov, aarcange,
raquini, anshuman.khandual, catalin.marinas, tiwai, will,
dave.hansen, jack, cl, jglisse, surenb, zokeefe, hannes, rientjes,
mhocko, rdunlap
On 15/05/25 8:51 am, Nico Pache wrote:
> Ugh... So sorry, I forgot to turn off the chain-reply-to.
>
> resending V7 *facepalm*
In the future you can just send the same version again with [RESEND]
prefixed in the subject, that prevents confusion.
>
> On Wed, May 14, 2025 at 9:03 PM Nico Pache <npache@redhat.com> wrote:
>>
>> The following series provides khugepaged and madvise collapse with the
>> capability to collapse anonymous memory regions to mTHPs.
>>
>> To achieve this we generalize the khugepaged functions to no longer depend
>> on PMD_ORDER. Then during the PMD scan, we keep track of chunks of pages
>> (defined by KHUGEPAGED_MTHP_MIN_ORDER) that are utilized. This info is
>> tracked using a bitmap. After the PMD scan is done, we do binary recursion
>> on the bitmap to find the optimal mTHP sizes for the PMD range. The
>> restriction on max_ptes_none is removed during the scan, to make sure we
>> account for the whole PMD range. When no mTHP size is enabled, the legacy
>> behavior of khugepaged is maintained. max_ptes_none will be scaled by the
>> attempted collapse order to determine how full a THP must be to be
>> eligible. If a mTHP collapse is attempted, but contains swapped out, or
>> shared pages, we dont perform the collapse.
>>
>> With the default max_ptes_none=511, the code should keep its most of its
>> original behavior. To exercise mTHP collapse we need to set
>> max_ptes_none<=255. With max_ptes_none > HPAGE_PMD_NR/2 you will
>> experience collapse "creep" and constantly promote mTHPs to the next
>> available size. This is due the fact that it will introduce at least 2x
>> the number of pages, and on a future scan will satisfy that condition once
>> again.
>>
>> Patch 1: Refactor/rename hpage_collapse
>> Patch 2: Some refactoring to combine madvise_collapse and khugepaged
>> Patch 3-5: Generalize khugepaged functions for arbitrary orders
>> Patch 6-9: The mTHP patches
>> Patch 10-11: Tracing/stats
>> Patch 12: Documentation
>>
>> ---------
>> Testing
>> ---------
>> - Built for x86_64, aarch64, ppc64le, and s390x
>> - selftests mm
>> - I created a test script that I used to push khugepaged to its limits
>> while monitoring a number of stats and tracepoints. The code is
>> available here[1] (Run in legacy mode for these changes and set mthp
>> sizes to inherit)
>> The summary from my testings was that there was no significant
>> regression noticed through this test. In some cases my changes had
>> better collapse latencies, and was able to scan more pages in the same
>> amount of time/work, but for the most part the results were consistent.
>> - redis testing. I tested these changes along with my defer changes
>> (see followup post for more details).
>> - some basic testing on 64k page size.
>> - lots of general use.
>>
>> V6 Changes:
>> - Dont release the anon_vma_lock early (like in the PMD case), as not all
>> pages are isolated.
>> - Define the PTE as null to avoid a uninitilized condition
>> - minor nits and newline cleanup
>> - make sure to unmap and unlock the pte for the swapin case
>> - change the revalidation to always check the PMD order (as this will make
>> sure that no other VMA spans it)
>>
>> V5 Changes [2]:
>> - switched the order of patches 1 and 2
>> - fixed some edge cases on the unified madvise_collapse and khugepaged
>> - Explained the "creep" some more in the docs
>> - fix EXCEED_SHARED vs EXCEED_SWAP accounting issue
>> - fix potential highmem issue caused by a early unmap of the PTE
>>
>> V4 Changes:
>> - Rebased onto mm-unstable
>> - small changes to Documentation
>>
>> V3 Changes:
>> - corrected legacy behavior for khugepaged and madvise_collapse
>> - added proper mTHP stat tracking
>> - Minor changes to prevent a nested lock on non-split-lock arches
>> - Took Devs version of alloc_charge_folio as it has the proper stats
>> - Skip cases were trying to collapse to a lower order would still fail
>> - Fixed cases were the bitmap was not being updated properly
>> - Moved Documentation update to this series instead of the defer set
>> - Minor bugs discovered during testing and review
>> - Minor "nit" cleanup
>>
>> V2 Changes:
>> - Minor bug fixes discovered during review and testing
>> - removed dynamic allocations for bitmaps, and made them stack based
>> - Adjusted bitmap offset from u8 to u16 to support 64k pagesize.
>> - Updated trace events to include collapsing order info.
>> - Scaled max_ptes_none by order rather than scaling to a 0-100 scale.
>> - No longer require a chunk to be fully utilized before setting the bit.
>> Use the same max_ptes_none scaling principle to achieve this.
>> - Skip mTHP collapse that requires swapin or shared handling. This helps
>> prevent some of the "creep" that was discovered in v1.
>>
>> [1] - https://gitlab.com/npache/khugepaged_mthp_test
>> [2] - https://lore.kernel.org/all/20250428181218.85925-1-npache@redhat.com/
>>
>> Dev Jain (1):
>> khugepaged: generalize alloc_charge_folio()
>>
>> Nico Pache (11):
>> khugepaged: rename hpage_collapse_* to khugepaged_*
>> introduce khugepaged_collapse_single_pmd to unify khugepaged and
>> madvise_collapse
>> khugepaged: generalize hugepage_vma_revalidate for mTHP support
>> khugepaged: generalize __collapse_huge_page_* for mTHP support
>> khugepaged: introduce khugepaged_scan_bitmap for mTHP support
>> khugepaged: add mTHP support
>> khugepaged: skip collapsing mTHP to smaller orders
>> khugepaged: avoid unnecessary mTHP collapse attempts
>> khugepaged: improve tracepoints for mTHP orders
>> khugepaged: add per-order mTHP khugepaged stats
>> Documentation: mm: update the admin guide for mTHP collapse
>>
>> Documentation/admin-guide/mm/transhuge.rst | 14 +-
>> include/linux/huge_mm.h | 5 +
>> include/linux/khugepaged.h | 4 +
>> include/trace/events/huge_memory.h | 34 +-
>> mm/huge_memory.c | 11 +
>> mm/khugepaged.c | 472 ++++++++++++++-------
>> 6 files changed, 382 insertions(+), 158 deletions(-)
>>
>> --
>> 2.49.0
>>
>
^ permalink raw reply [flat|nested] 16+ messages in thread
* Re: [PATCH v6 00/12] khugepaged: mTHP support
2025-05-15 6:45 ` Dev Jain
@ 2025-05-16 11:54 ` Nico Pache
0 siblings, 0 replies; 16+ messages in thread
From: Nico Pache @ 2025-05-16 11:54 UTC (permalink / raw)
To: Dev Jain
Cc: linux-mm, linux-doc, linux-kernel, linux-trace-kernel, david, ziy,
baolin.wang, lorenzo.stoakes, Liam.Howlett, ryan.roberts, corbet,
rostedt, mhiramat, mathieu.desnoyers, akpm, baohua, willy, peterx,
wangkefeng.wang, usamaarif642, sunnanyong, vishal.moola,
thomas.hellstrom, yang, kirill.shutemov, aarcange, raquini,
anshuman.khandual, catalin.marinas, tiwai, will, dave.hansen,
jack, cl, jglisse, surenb, zokeefe, hannes, rientjes, mhocko,
rdunlap
On Thu, May 15, 2025 at 12:45 AM Dev Jain <dev.jain@arm.com> wrote:
>
>
>
> On 15/05/25 8:51 am, Nico Pache wrote:
> > Ugh... So sorry, I forgot to turn off the chain-reply-to.
> >
> > resending V7 *facepalm*
>
> In the future you can just send the same version again with [RESEND]
> prefixed in the subject, that prevents confusion.
Thanks I'll do that next time.
>
> >
> > On Wed, May 14, 2025 at 9:03 PM Nico Pache <npache@redhat.com> wrote:
> >>
> >> The following series provides khugepaged and madvise collapse with the
> >> capability to collapse anonymous memory regions to mTHPs.
> >>
> >> To achieve this we generalize the khugepaged functions to no longer depend
> >> on PMD_ORDER. Then during the PMD scan, we keep track of chunks of pages
> >> (defined by KHUGEPAGED_MTHP_MIN_ORDER) that are utilized. This info is
> >> tracked using a bitmap. After the PMD scan is done, we do binary recursion
> >> on the bitmap to find the optimal mTHP sizes for the PMD range. The
> >> restriction on max_ptes_none is removed during the scan, to make sure we
> >> account for the whole PMD range. When no mTHP size is enabled, the legacy
> >> behavior of khugepaged is maintained. max_ptes_none will be scaled by the
> >> attempted collapse order to determine how full a THP must be to be
> >> eligible. If a mTHP collapse is attempted, but contains swapped out, or
> >> shared pages, we dont perform the collapse.
> >>
> >> With the default max_ptes_none=511, the code should keep its most of its
> >> original behavior. To exercise mTHP collapse we need to set
> >> max_ptes_none<=255. With max_ptes_none > HPAGE_PMD_NR/2 you will
> >> experience collapse "creep" and constantly promote mTHPs to the next
> >> available size. This is due the fact that it will introduce at least 2x
> >> the number of pages, and on a future scan will satisfy that condition once
> >> again.
> >>
> >> Patch 1: Refactor/rename hpage_collapse
> >> Patch 2: Some refactoring to combine madvise_collapse and khugepaged
> >> Patch 3-5: Generalize khugepaged functions for arbitrary orders
> >> Patch 6-9: The mTHP patches
> >> Patch 10-11: Tracing/stats
> >> Patch 12: Documentation
> >>
> >> ---------
> >> Testing
> >> ---------
> >> - Built for x86_64, aarch64, ppc64le, and s390x
> >> - selftests mm
> >> - I created a test script that I used to push khugepaged to its limits
> >> while monitoring a number of stats and tracepoints. The code is
> >> available here[1] (Run in legacy mode for these changes and set mthp
> >> sizes to inherit)
> >> The summary from my testings was that there was no significant
> >> regression noticed through this test. In some cases my changes had
> >> better collapse latencies, and was able to scan more pages in the same
> >> amount of time/work, but for the most part the results were consistent.
> >> - redis testing. I tested these changes along with my defer changes
> >> (see followup post for more details).
> >> - some basic testing on 64k page size.
> >> - lots of general use.
> >>
> >> V6 Changes:
> >> - Dont release the anon_vma_lock early (like in the PMD case), as not all
> >> pages are isolated.
> >> - Define the PTE as null to avoid a uninitilized condition
> >> - minor nits and newline cleanup
> >> - make sure to unmap and unlock the pte for the swapin case
> >> - change the revalidation to always check the PMD order (as this will make
> >> sure that no other VMA spans it)
> >>
> >> V5 Changes [2]:
> >> - switched the order of patches 1 and 2
> >> - fixed some edge cases on the unified madvise_collapse and khugepaged
> >> - Explained the "creep" some more in the docs
> >> - fix EXCEED_SHARED vs EXCEED_SWAP accounting issue
> >> - fix potential highmem issue caused by a early unmap of the PTE
> >>
> >> V4 Changes:
> >> - Rebased onto mm-unstable
> >> - small changes to Documentation
> >>
> >> V3 Changes:
> >> - corrected legacy behavior for khugepaged and madvise_collapse
> >> - added proper mTHP stat tracking
> >> - Minor changes to prevent a nested lock on non-split-lock arches
> >> - Took Devs version of alloc_charge_folio as it has the proper stats
> >> - Skip cases were trying to collapse to a lower order would still fail
> >> - Fixed cases were the bitmap was not being updated properly
> >> - Moved Documentation update to this series instead of the defer set
> >> - Minor bugs discovered during testing and review
> >> - Minor "nit" cleanup
> >>
> >> V2 Changes:
> >> - Minor bug fixes discovered during review and testing
> >> - removed dynamic allocations for bitmaps, and made them stack based
> >> - Adjusted bitmap offset from u8 to u16 to support 64k pagesize.
> >> - Updated trace events to include collapsing order info.
> >> - Scaled max_ptes_none by order rather than scaling to a 0-100 scale.
> >> - No longer require a chunk to be fully utilized before setting the bit.
> >> Use the same max_ptes_none scaling principle to achieve this.
> >> - Skip mTHP collapse that requires swapin or shared handling. This helps
> >> prevent some of the "creep" that was discovered in v1.
> >>
> >> [1] - https://gitlab.com/npache/khugepaged_mthp_test
> >> [2] - https://lore.kernel.org/all/20250428181218.85925-1-npache@redhat.com/
> >>
> >> Dev Jain (1):
> >> khugepaged: generalize alloc_charge_folio()
> >>
> >> Nico Pache (11):
> >> khugepaged: rename hpage_collapse_* to khugepaged_*
> >> introduce khugepaged_collapse_single_pmd to unify khugepaged and
> >> madvise_collapse
> >> khugepaged: generalize hugepage_vma_revalidate for mTHP support
> >> khugepaged: generalize __collapse_huge_page_* for mTHP support
> >> khugepaged: introduce khugepaged_scan_bitmap for mTHP support
> >> khugepaged: add mTHP support
> >> khugepaged: skip collapsing mTHP to smaller orders
> >> khugepaged: avoid unnecessary mTHP collapse attempts
> >> khugepaged: improve tracepoints for mTHP orders
> >> khugepaged: add per-order mTHP khugepaged stats
> >> Documentation: mm: update the admin guide for mTHP collapse
> >>
> >> Documentation/admin-guide/mm/transhuge.rst | 14 +-
> >> include/linux/huge_mm.h | 5 +
> >> include/linux/khugepaged.h | 4 +
> >> include/trace/events/huge_memory.h | 34 +-
> >> mm/huge_memory.c | 11 +
> >> mm/khugepaged.c | 472 ++++++++++++++-------
> >> 6 files changed, 382 insertions(+), 158 deletions(-)
> >>
> >> --
> >> 2.49.0
> >>
> >
>
^ permalink raw reply [flat|nested] 16+ messages in thread
end of thread, other threads:[~2025-05-16 11:55 UTC | newest]
Thread overview: 16+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2025-05-15 3:03 [PATCH v6 00/12] khugepaged: mTHP support Nico Pache
2025-05-15 3:03 ` [PATCH v6 01/12] khugepaged: rename hpage_collapse_* to khugepaged_* Nico Pache
2025-05-15 3:03 ` [PATCH v6 02/12] introduce khugepaged_collapse_single_pmd to unify khugepaged and madvise_collapse Nico Pache
2025-05-15 3:03 ` [PATCH v6 03/12] khugepaged: generalize hugepage_vma_revalidate for mTHP support Nico Pache
2025-05-15 3:03 ` [PATCH v6 04/12] khugepaged: generalize alloc_charge_folio() Nico Pache
2025-05-15 3:03 ` [PATCH v6 05/12] khugepaged: generalize __collapse_huge_page_* for mTHP support Nico Pache
2025-05-15 3:03 ` [PATCH v6 06/12] khugepaged: introduce khugepaged_scan_bitmap " Nico Pache
2025-05-15 3:03 ` [PATCH v6 07/12] khugepaged: add " Nico Pache
2025-05-15 3:03 ` [PATCH v6 08/12] khugepaged: skip collapsing mTHP to smaller orders Nico Pache
2025-05-15 3:03 ` [PATCH v6 09/12] khugepaged: avoid unnecessary mTHP collapse attempts Nico Pache
2025-05-15 3:03 ` [PATCH v6 10/12] khugepaged: improve tracepoints for mTHP orders Nico Pache
2025-05-15 3:03 ` [PATCH v6 11/12] khugepaged: add per-order mTHP khugepaged stats Nico Pache
2025-05-15 3:03 ` [PATCH v6 12/12] Documentation: mm: update the admin guide for mTHP collapse Nico Pache
2025-05-15 3:21 ` [PATCH v6 00/12] khugepaged: mTHP support Nico Pache
2025-05-15 6:45 ` Dev Jain
2025-05-16 11:54 ` Nico Pache
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