* [PATCH v3 01/12] introduce khugepaged_collapse_single_pmd to unify khugepaged and madvise_collapse
2025-04-14 22:05 [PATCH v3 00/12] khugepaged: mTHP support Nico Pache
@ 2025-04-14 22:05 ` Nico Pache
2025-04-14 22:05 ` [PATCH v3 02/12] khugepaged: rename hpage_collapse_* to khugepaged_* Nico Pache
` (10 subsequent siblings)
11 siblings, 0 replies; 17+ messages in thread
From: Nico Pache @ 2025-04-14 22:05 UTC (permalink / raw)
To: linux-mm, linux-doc, linux-kernel, linux-trace-kernel
Cc: akpm, corbet, rostedt, mhiramat, mathieu.desnoyers, david, baohua,
baolin.wang, ryan.roberts, willy, peterx, ziy, wangkefeng.wang,
usamaarif642, sunnanyong, vishal.moola, thomas.hellstrom, yang,
kirill.shutemov, aarcange, raquini, dev.jain, anshuman.khandual,
catalin.marinas, tiwai, will, dave.hansen, jack, cl, jglisse,
surenb, zokeefe, hannes, rientjes, mhocko
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.
Signed-off-by: Nico Pache <npache@redhat.com>
---
mm/khugepaged.c | 92 ++++++++++++++++++++++++-------------------------
1 file changed, 46 insertions(+), 46 deletions(-)
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index cc945c6ab3bd..c23d80ed9c9c 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -2363,6 +2363,48 @@ static int hpage_collapse_scan_file(struct mm_struct *mm, unsigned long addr,
}
#endif
+/*
+ * 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;
+ unsigned long tva_flags = cc->is_khugepaged ? TVA_ENFORCE_SYSFS : 0;
+
+ if (thp_vma_allowable_order(vma, vma->vm_flags,
+ tva_flags, PMD_ORDER)) {
+ 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 = hpage_collapse_scan_file(mm, addr, file, pgoff,
+ cc);
+ fput(file);
+ if (result == SCAN_PTE_MAPPED_HUGEPAGE) {
+ mmap_read_lock(mm);
+ if (hpage_collapse_test_exit_or_disable(mm))
+ goto end;
+ result = collapse_pte_mapped_thp(mm, addr,
+ !cc->is_khugepaged);
+ mmap_read_unlock(mm);
+ }
+ } else {
+ result = hpage_collapse_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)
@@ -2437,33 +2479,9 @@ 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 (IS_ENABLED(CONFIG_SHMEM) && !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);
/* move to next address */
khugepaged_scan.address += HPAGE_PMD_SIZE;
@@ -2783,36 +2801,18 @@ 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 (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 = 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:
--
2.48.1
^ permalink raw reply related [flat|nested] 17+ messages in thread* [PATCH v3 02/12] khugepaged: rename hpage_collapse_* to khugepaged_*
2025-04-14 22:05 [PATCH v3 00/12] khugepaged: mTHP support Nico Pache
2025-04-14 22:05 ` [PATCH v3 01/12] introduce khugepaged_collapse_single_pmd to unify khugepaged and madvise_collapse Nico Pache
@ 2025-04-14 22:05 ` Nico Pache
2025-04-14 22:05 ` [PATCH v3 03/12] khugepaged: generalize hugepage_vma_revalidate for mTHP support Nico Pache
` (9 subsequent siblings)
11 siblings, 0 replies; 17+ messages in thread
From: Nico Pache @ 2025-04-14 22:05 UTC (permalink / raw)
To: linux-mm, linux-doc, linux-kernel, linux-trace-kernel
Cc: akpm, corbet, rostedt, mhiramat, mathieu.desnoyers, david, baohua,
baolin.wang, ryan.roberts, willy, peterx, ziy, wangkefeng.wang,
usamaarif642, sunnanyong, vishal.moola, thomas.hellstrom, yang,
kirill.shutemov, aarcange, raquini, dev.jain, anshuman.khandual,
catalin.marinas, tiwai, will, dave.hansen, jack, cl, jglisse,
surenb, zokeefe, hannes, rientjes, mhocko
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.
Signed-off-by: Nico Pache <npache@redhat.com>
---
mm/khugepaged.c | 50 ++++++++++++++++++++++++-------------------------
1 file changed, 25 insertions(+), 25 deletions(-)
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index c23d80ed9c9c..9a1242368cba 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);
@@ -1742,7 +1742,7 @@ 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
@@ -2264,7 +2264,7 @@ 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)
{
@@ -2309,7 +2309,7 @@ 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;
}
@@ -2355,7 +2355,7 @@ static int hpage_collapse_scan_file(struct mm_struct *mm, unsigned long addr,
return result;
}
#else
-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)
{
@@ -2383,19 +2383,19 @@ static int khugepaged_collapse_single_pmd(unsigned long addr,
mmap_read_unlock(mm);
*mmap_locked = false;
- result = hpage_collapse_scan_file(mm, addr, file, pgoff,
+ result = khugepaged_scan_file(mm, addr, file, pgoff,
cc);
fput(file);
if (result == SCAN_PTE_MAPPED_HUGEPAGE) {
mmap_read_lock(mm);
- if (hpage_collapse_test_exit_or_disable(mm))
+ if (khugepaged_test_exit_or_disable(mm))
goto end;
result = collapse_pte_mapped_thp(mm, addr,
!cc->is_khugepaged);
mmap_read_unlock(mm);
}
} else {
- result = hpage_collapse_scan_pmd(mm, vma, addr,
+ result = khugepaged_scan_pmd(mm, vma, addr,
mmap_locked, cc);
}
if (cc->is_khugepaged && result == SCAN_SUCCEED)
@@ -2443,7 +2443,7 @@ 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);
@@ -2451,7 +2451,7 @@ 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;
}
@@ -2473,7 +2473,7 @@ 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 ||
@@ -2509,7 +2509,7 @@ 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
--
2.48.1
^ permalink raw reply related [flat|nested] 17+ messages in thread* [PATCH v3 03/12] khugepaged: generalize hugepage_vma_revalidate for mTHP support
2025-04-14 22:05 [PATCH v3 00/12] khugepaged: mTHP support Nico Pache
2025-04-14 22:05 ` [PATCH v3 01/12] introduce khugepaged_collapse_single_pmd to unify khugepaged and madvise_collapse Nico Pache
2025-04-14 22:05 ` [PATCH v3 02/12] khugepaged: rename hpage_collapse_* to khugepaged_* Nico Pache
@ 2025-04-14 22:05 ` Nico Pache
2025-04-14 22:05 ` [PATCH v3 04/12] khugepaged: generalize alloc_charge_folio() Nico Pache
` (8 subsequent siblings)
11 siblings, 0 replies; 17+ messages in thread
From: Nico Pache @ 2025-04-14 22:05 UTC (permalink / raw)
To: linux-mm, linux-doc, linux-kernel, linux-trace-kernel
Cc: akpm, corbet, rostedt, mhiramat, mathieu.desnoyers, david, baohua,
baolin.wang, ryan.roberts, willy, peterx, ziy, wangkefeng.wang,
usamaarif642, sunnanyong, vishal.moola, thomas.hellstrom, yang,
kirill.shutemov, aarcange, raquini, dev.jain, anshuman.khandual,
catalin.marinas, tiwai, will, dave.hansen, jack, cl, jglisse,
surenb, zokeefe, hannes, rientjes, mhocko
For khugepaged to support different mTHP orders, we must generalize this
function for arbitrary orders.
No functional change in this patch.
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 | 12 ++++++------
1 file changed, 6 insertions(+), 6 deletions(-)
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 9a1242368cba..61c6ef8fa604 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;
@@ -932,9 +932,9 @@ static int hugepage_vma_revalidate(struct mm_struct *mm, unsigned long address,
if (!vma)
return SCAN_VMA_NULL;
- if (!thp_vma_suitable_order(vma, address, PMD_ORDER))
+ if (!thp_vma_suitable_order(vma, address, 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 */
@@ -2790,7 +2790,7 @@ 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;
--
2.48.1
^ permalink raw reply related [flat|nested] 17+ messages in thread* [PATCH v3 04/12] khugepaged: generalize alloc_charge_folio()
2025-04-14 22:05 [PATCH v3 00/12] khugepaged: mTHP support Nico Pache
` (2 preceding siblings ...)
2025-04-14 22:05 ` [PATCH v3 03/12] khugepaged: generalize hugepage_vma_revalidate for mTHP support Nico Pache
@ 2025-04-14 22:05 ` Nico Pache
2025-04-14 22:05 ` [PATCH v3 05/12] khugepaged: generalize __collapse_huge_page_* for mTHP support Nico Pache
` (7 subsequent siblings)
11 siblings, 0 replies; 17+ messages in thread
From: Nico Pache @ 2025-04-14 22:05 UTC (permalink / raw)
To: linux-mm, linux-doc, linux-kernel, linux-trace-kernel
Cc: akpm, corbet, rostedt, mhiramat, mathieu.desnoyers, david, baohua,
baolin.wang, ryan.roberts, willy, peterx, ziy, wangkefeng.wang,
usamaarif642, sunnanyong, vishal.moola, thomas.hellstrom, yang,
kirill.shutemov, aarcange, raquini, dev.jain, anshuman.khandual,
catalin.marinas, tiwai, will, dave.hansen, jack, cl, jglisse,
surenb, zokeefe, hannes, rientjes, mhocko
From: Dev Jain <dev.jain@arm.com>
Pass order to alloc_charge_folio() and update mTHP statistics.
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 e893d546a49f..2acd9c1fc558 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 2a47682d1ab7..6db73d2d0962 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 61c6ef8fa604..78caa6d227c3 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;
@@ -1849,7 +1854,7 @@ 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;
--
2.48.1
^ permalink raw reply related [flat|nested] 17+ messages in thread* [PATCH v3 05/12] khugepaged: generalize __collapse_huge_page_* for mTHP support
2025-04-14 22:05 [PATCH v3 00/12] khugepaged: mTHP support Nico Pache
` (3 preceding siblings ...)
2025-04-14 22:05 ` [PATCH v3 04/12] khugepaged: generalize alloc_charge_folio() Nico Pache
@ 2025-04-14 22:05 ` Nico Pache
2025-04-14 22:05 ` [PATCH v3 06/12] khugepaged: introduce khugepaged_scan_bitmap " Nico Pache
` (6 subsequent siblings)
11 siblings, 0 replies; 17+ messages in thread
From: Nico Pache @ 2025-04-14 22:05 UTC (permalink / raw)
To: linux-mm, linux-doc, linux-kernel, linux-trace-kernel
Cc: akpm, corbet, rostedt, mhiramat, mathieu.desnoyers, david, baohua,
baolin.wang, ryan.roberts, willy, peterx, ziy, wangkefeng.wang,
usamaarif642, sunnanyong, vishal.moola, thomas.hellstrom, yang,
kirill.shutemov, aarcange, raquini, dev.jain, anshuman.khandual,
catalin.marinas, tiwai, will, dave.hansen, jack, cl, jglisse,
surenb, zokeefe, hannes, rientjes, mhocko
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.
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 | 46 ++++++++++++++++++++++++++++------------------
1 file changed, 28 insertions(+), 18 deletions(-)
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 78caa6d227c3..dfecedc6a515 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 +1039,12 @@ 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) {
+ result = SCAN_EXCEED_SWAP_PTE;
+ goto out;
+ }
+
vmf.pte = pte;
vmf.ptl = ptl;
ret = do_swap_page(&vmf);
@@ -1154,7 +1164,7 @@ 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 +1211,7 @@ 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 +1241,7 @@ 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;
--
2.48.1
^ permalink raw reply related [flat|nested] 17+ messages in thread* [PATCH v3 06/12] khugepaged: introduce khugepaged_scan_bitmap for mTHP support
2025-04-14 22:05 [PATCH v3 00/12] khugepaged: mTHP support Nico Pache
` (4 preceding siblings ...)
2025-04-14 22:05 ` [PATCH v3 05/12] khugepaged: generalize __collapse_huge_page_* for mTHP support Nico Pache
@ 2025-04-14 22:05 ` Nico Pache
2025-04-14 23:06 ` Nico Pache
2025-04-14 23:18 ` [PATCH v4 " Nico Pache
2025-04-14 22:05 ` [PATCH v3 07/12] khugepaged: add " Nico Pache
` (5 subsequent siblings)
11 siblings, 2 replies; 17+ messages in thread
From: Nico Pache @ 2025-04-14 22:05 UTC (permalink / raw)
To: linux-mm, linux-doc, linux-kernel, linux-trace-kernel
Cc: akpm, corbet, rostedt, mhiramat, mathieu.desnoyers, david, baohua,
baolin.wang, ryan.roberts, willy, peterx, ziy, wangkefeng.wang,
usamaarif642, sunnanyong, vishal.moola, thomas.hellstrom, yang,
kirill.shutemov, aarcange, raquini, dev.jain, anshuman.khandual,
catalin.marinas, tiwai, will, dave.hansen, jack, cl, jglisse,
surenb, zokeefe, hannes, rientjes, mhocko
khugepaged scans PMD ranges for potential collapse to a hugepage. To add
mTHP support we use this scan to instead record chunks of fully utilized
sections of the PMD.
create a bitmap to represent a PMD in order MIN_MTHP_ORDER chunks.
by default we will set this to order 3. The reasoning is that for 4K 512
PMD size this results in a 64 bit bitmap which has some optimizations.
For other arches like ARM64 64K, we can set a larger order if needed.
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 PMD.
max_ptes_none is used as a scale to determine how "full" an order must
be before being considered for collapse.
If a order is set to "always" lets always collapse to that order in a
greedy manner.
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 1f46046080f5..60d41215bc1a 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 3
+#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 dfecedc6a515..5a3be30096fc 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;
@@ -1118,7 +1131,8 @@ 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;
@@ -1137,8 +1151,12 @@ 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)
@@ -1273,12 +1291,72 @@ 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,
@@ -1445,9 +1523,7 @@ 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->page, writable, referenced,
--
2.48.1
^ permalink raw reply related [flat|nested] 17+ messages in thread* Re: [PATCH v3 06/12] khugepaged: introduce khugepaged_scan_bitmap for mTHP support
2025-04-14 22:05 ` [PATCH v3 06/12] khugepaged: introduce khugepaged_scan_bitmap " Nico Pache
@ 2025-04-14 23:06 ` Nico Pache
2025-04-14 23:40 ` Nico Pache
2025-04-14 23:18 ` [PATCH v4 " Nico Pache
1 sibling, 1 reply; 17+ messages in thread
From: Nico Pache @ 2025-04-14 23:06 UTC (permalink / raw)
To: linux-mm, linux-doc, linux-kernel, linux-trace-kernel
Cc: akpm, corbet, rostedt, mhiramat, mathieu.desnoyers, david, baohua,
baolin.wang, ryan.roberts, willy, peterx, ziy, wangkefeng.wang,
usamaarif642, sunnanyong, vishal.moola, thomas.hellstrom, yang,
kirill.shutemov, aarcange, raquini, dev.jain, anshuman.khandual,
catalin.marinas, tiwai, will, dave.hansen, jack, cl, jglisse,
surenb, zokeefe, hannes, rientjes, mhocko
On Mon, Apr 14, 2025 at 4:07 PM Nico Pache <npache@redhat.com> wrote:
>
> khugepaged scans PMD ranges for potential collapse to a hugepage. To add
> mTHP support we use this scan to instead record chunks of fully utilized
> sections of the PMD.
>
> create a bitmap to represent a PMD in order MIN_MTHP_ORDER chunks.
> by default we will set this to order 3. The reasoning is that for 4K 512
> PMD size this results in a 64 bit bitmap which has some optimizations.
> For other arches like ARM64 64K, we can set a larger order if needed.
>
> 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 PMD.
>
> max_ptes_none is used as a scale to determine how "full" an order must
> be before being considered for collapse.
>
> If a order is set to "always" lets always collapse to that order in a
> greedy manner.
>
> 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 1f46046080f5..60d41215bc1a 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 3
Somehow managed to drop
#define KHUGEPAGED_MIN_MTHP_ORDER 2
When cleaning up my patches.
Sending a V4 of just this patch in reply to this email.
Sorry for the noise...
> +#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 dfecedc6a515..5a3be30096fc 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;
> @@ -1118,7 +1131,8 @@ 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;
> @@ -1137,8 +1151,12 @@ 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)
> @@ -1273,12 +1291,72 @@ 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,
> @@ -1445,9 +1523,7 @@ 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->page, writable, referenced,
> --
> 2.48.1
>
^ permalink raw reply [flat|nested] 17+ messages in thread* Re: [PATCH v3 06/12] khugepaged: introduce khugepaged_scan_bitmap for mTHP support
2025-04-14 23:06 ` Nico Pache
@ 2025-04-14 23:40 ` Nico Pache
0 siblings, 0 replies; 17+ messages in thread
From: Nico Pache @ 2025-04-14 23:40 UTC (permalink / raw)
To: linux-mm, linux-doc, linux-kernel, linux-trace-kernel
Cc: akpm, corbet, rostedt, mhiramat, mathieu.desnoyers, david, baohua,
baolin.wang, ryan.roberts, willy, peterx, ziy, wangkefeng.wang,
usamaarif642, sunnanyong, vishal.moola, thomas.hellstrom, yang,
kirill.shutemov, aarcange, raquini, dev.jain, anshuman.khandual,
catalin.marinas, tiwai, will, dave.hansen, jack, cl, jglisse,
surenb, zokeefe, hannes, rientjes, mhocko
On Mon, Apr 14, 2025 at 5:06 PM Nico Pache <npache@redhat.com> wrote:
>
> On Mon, Apr 14, 2025 at 4:07 PM Nico Pache <npache@redhat.com> wrote:
> >
> > khugepaged scans PMD ranges for potential collapse to a hugepage. To add
> > mTHP support we use this scan to instead record chunks of fully utilized
> > sections of the PMD.
> >
> > create a bitmap to represent a PMD in order MIN_MTHP_ORDER chunks.
> > by default we will set this to order 3. The reasoning is that for 4K 512
> > PMD size this results in a 64 bit bitmap which has some optimizations.
> > For other arches like ARM64 64K, we can set a larger order if needed.
> >
> > 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 PMD.
> >
> > max_ptes_none is used as a scale to determine how "full" an order must
> > be before being considered for collapse.
> >
> > If a order is set to "always" lets always collapse to that order in a
> > greedy manner.
> >
> > 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 1f46046080f5..60d41215bc1a 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 3
> Somehow managed to drop
> #define KHUGEPAGED_MIN_MTHP_ORDER 2
> When cleaning up my patches.
>
> Sending a V4 of just this patch in reply to this email.
>
> Sorry for the noise...
Sorry more noise...
The #define KHUGEPAGED_MIN_MTHP_ORDER 2 fixup got merged into the
wrong commit, and is actually in 07/12. If we take this V4, the merge
will clean up the 07/12 commit with no additional changes.
If sending out a V4 of 07/12 is needed please let me know.
>
>
>
> > +#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 dfecedc6a515..5a3be30096fc 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;
> > @@ -1118,7 +1131,8 @@ 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;
> > @@ -1137,8 +1151,12 @@ 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)
> > @@ -1273,12 +1291,72 @@ 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,
> > @@ -1445,9 +1523,7 @@ 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->page, writable, referenced,
> > --
> > 2.48.1
> >
^ permalink raw reply [flat|nested] 17+ messages in thread
* [PATCH v4 06/12] khugepaged: introduce khugepaged_scan_bitmap for mTHP support
2025-04-14 22:05 ` [PATCH v3 06/12] khugepaged: introduce khugepaged_scan_bitmap " Nico Pache
2025-04-14 23:06 ` Nico Pache
@ 2025-04-14 23:18 ` Nico Pache
1 sibling, 0 replies; 17+ messages in thread
From: Nico Pache @ 2025-04-14 23:18 UTC (permalink / raw)
To: npache
Cc: aarcange, akpm, anshuman.khandual, baohua, baolin.wang,
catalin.marinas, cl, corbet, dave.hansen, david, dev.jain, hannes,
jack, jglisse, kirill.shutemov, linux-doc, linux-kernel, linux-mm,
linux-trace-kernel, mathieu.desnoyers, mhiramat, mhocko, peterx,
raquini, rientjes, rostedt, ryan.roberts, sunnanyong, surenb,
thomas.hellstrom, tiwai, usamaarif642, vishal.moola,
wangkefeng.wang, will, willy, yang, ziy, zokeefe
khugepaged scans 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 PMD.
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 1f46046080f5..18fe6eb5051d 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 dfecedc6a515..5a3be30096fc 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;
@@ -1118,7 +1131,8 @@ 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;
@@ -1137,8 +1151,12 @@ 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)
@@ -1273,12 +1291,72 @@ 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,
@@ -1445,9 +1523,7 @@ 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->page, writable, referenced,
--
2.48.1
^ permalink raw reply related [flat|nested] 17+ messages in thread
* [PATCH v3 07/12] khugepaged: add mTHP support
2025-04-14 22:05 [PATCH v3 00/12] khugepaged: mTHP support Nico Pache
` (5 preceding siblings ...)
2025-04-14 22:05 ` [PATCH v3 06/12] khugepaged: introduce khugepaged_scan_bitmap " Nico Pache
@ 2025-04-14 22:05 ` Nico Pache
2025-04-14 22:05 ` [PATCH v3 08/12] khugepaged: skip collapsing mTHP to smaller orders Nico Pache
` (4 subsequent siblings)
11 siblings, 0 replies; 17+ messages in thread
From: Nico Pache @ 2025-04-14 22:05 UTC (permalink / raw)
To: linux-mm, linux-doc, linux-kernel, linux-trace-kernel
Cc: akpm, corbet, rostedt, mhiramat, mathieu.desnoyers, david, baohua,
baolin.wang, ryan.roberts, willy, peterx, ziy, wangkefeng.wang,
usamaarif642, sunnanyong, vishal.moola, thomas.hellstrom, yang,
kirill.shutemov, aarcange, raquini, dev.jain, anshuman.khandual,
catalin.marinas, tiwai, will, dave.hansen, jack, cl, jglisse,
surenb, zokeefe, hannes, rientjes, mhocko
Introduce the ability for khugepaged to collapse to different mTHP sizes.
While scanning PMD ranges for potential collapse candidates, keep track
of pages in MIN_MTHP_ORDER chunks via a bitmap. Each bit represents a
utilized region of order 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.
Signed-off-by: Nico Pache <npache@redhat.com>
---
include/linux/khugepaged.h | 2 +-
mm/khugepaged.c | 122 ++++++++++++++++++++++++++-----------
2 files changed, 89 insertions(+), 35 deletions(-)
diff --git a/include/linux/khugepaged.h b/include/linux/khugepaged.h
index 60d41215bc1a..18fe6eb5051d 100644
--- a/include/linux/khugepaged.h
+++ b/include/linux/khugepaged.h
@@ -1,7 +1,7 @@
/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _LINUX_KHUGEPAGED_H
#define _LINUX_KHUGEPAGED_H
-#define KHUGEPAGED_MIN_MTHP_ORDER 3
+#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))
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 5a3be30096fc..de09de5a3f28 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -1136,13 +1136,14 @@ 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, 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);
@@ -1158,12 +1159,13 @@ 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;
@@ -1181,13 +1183,14 @@ 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
@@ -1197,7 +1200,7 @@ 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 */
@@ -1208,11 +1211,12 @@ 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
@@ -1226,10 +1230,10 @@ 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;
@@ -1258,8 +1262,8 @@ static int collapse_huge_page(struct mm_struct *mm, unsigned long address,
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);
+ vma, _address, pte_ptl,
+ &compound_pagelist, order);
pte_unmap(pte);
if (unlikely(result != SCAN_SUCCEED))
goto out_up_write;
@@ -1270,20 +1274,35 @@ static int collapse_huge_page(struct mm_struct *mm, unsigned long address,
* write.
*/
__folio_mark_uptodate(folio);
- pgtable = pmd_pgtable(_pmd);
-
- _pmd = mk_huge_pmd(&folio->page, 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 = mk_huge_pmd(&folio->page, 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
+ 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;
@@ -1364,31 +1383,58 @@ 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;
@@ -1411,10 +1457,11 @@ 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;
@@ -1510,6 +1557,7 @@ static int khugepaged_scan_pmd(struct mm_struct *mm,
address)))
referenced++;
}
+
if (!writable) {
result = SCAN_PAGE_RO;
} else if (cc->is_khugepaged &&
@@ -1522,8 +1570,12 @@ 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->page, writable, referenced,
@@ -2479,11 +2531,13 @@ static int khugepaged_collapse_single_pmd(unsigned long addr,
fput(file);
if (result == SCAN_PTE_MAPPED_HUGEPAGE) {
mmap_read_lock(mm);
+ *mmap_locked = true;
if (khugepaged_test_exit_or_disable(mm))
goto end;
result = collapse_pte_mapped_thp(mm, addr,
!cc->is_khugepaged);
mmap_read_unlock(mm);
+ *mmap_locked = false;
}
} else {
result = khugepaged_scan_pmd(mm, vma, addr,
--
2.48.1
^ permalink raw reply related [flat|nested] 17+ messages in thread* [PATCH v3 08/12] khugepaged: skip collapsing mTHP to smaller orders
2025-04-14 22:05 [PATCH v3 00/12] khugepaged: mTHP support Nico Pache
` (6 preceding siblings ...)
2025-04-14 22:05 ` [PATCH v3 07/12] khugepaged: add " Nico Pache
@ 2025-04-14 22:05 ` Nico Pache
2025-04-14 22:05 ` [PATCH v3 09/12] khugepaged: avoid unnecessary mTHP collapse attempts Nico Pache
` (3 subsequent siblings)
11 siblings, 0 replies; 17+ messages in thread
From: Nico Pache @ 2025-04-14 22:05 UTC (permalink / raw)
To: linux-mm, linux-doc, linux-kernel, linux-trace-kernel
Cc: akpm, corbet, rostedt, mhiramat, mathieu.desnoyers, david, baohua,
baolin.wang, ryan.roberts, willy, peterx, ziy, wangkefeng.wang,
usamaarif642, sunnanyong, vishal.moola, thomas.hellstrom, yang,
kirill.shutemov, aarcange, raquini, dev.jain, anshuman.khandual,
catalin.marinas, tiwai, will, dave.hansen, jack, cl, jglisse,
surenb, zokeefe, hannes, rientjes, mhocko
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/
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 de09de5a3f28..114056276003 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 &&
--
2.48.1
^ permalink raw reply related [flat|nested] 17+ messages in thread* [PATCH v3 09/12] khugepaged: avoid unnecessary mTHP collapse attempts
2025-04-14 22:05 [PATCH v3 00/12] khugepaged: mTHP support Nico Pache
` (7 preceding siblings ...)
2025-04-14 22:05 ` [PATCH v3 08/12] khugepaged: skip collapsing mTHP to smaller orders Nico Pache
@ 2025-04-14 22:05 ` Nico Pache
2025-04-14 22:05 ` [PATCH v3 10/12] khugepaged: improve tracepoints for mTHP orders Nico Pache
` (2 subsequent siblings)
11 siblings, 0 replies; 17+ messages in thread
From: Nico Pache @ 2025-04-14 22:05 UTC (permalink / raw)
To: linux-mm, linux-doc, linux-kernel, linux-trace-kernel
Cc: akpm, corbet, rostedt, mhiramat, mathieu.desnoyers, david, baohua,
baolin.wang, ryan.roberts, willy, peterx, ziy, wangkefeng.wang,
usamaarif642, sunnanyong, vishal.moola, thomas.hellstrom, yang,
kirill.shutemov, aarcange, raquini, dev.jain, anshuman.khandual,
catalin.marinas, tiwai, will, dave.hansen, jack, cl, jglisse,
surenb, zokeefe, hannes, rientjes, mhocko
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 114056276003..86e4c5100181 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -1366,6 +1366,23 @@ 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:
--
2.48.1
^ permalink raw reply related [flat|nested] 17+ messages in thread* [PATCH v3 10/12] khugepaged: improve tracepoints for mTHP orders
2025-04-14 22:05 [PATCH v3 00/12] khugepaged: mTHP support Nico Pache
` (8 preceding siblings ...)
2025-04-14 22:05 ` [PATCH v3 09/12] khugepaged: avoid unnecessary mTHP collapse attempts Nico Pache
@ 2025-04-14 22:05 ` Nico Pache
2025-04-14 22:05 ` [PATCH v3 11/12] khugepaged: add per-order mTHP khugepaged stats Nico Pache
2025-04-14 22:05 ` [PATCH v3 12/12] Documentation: mm: update the admin guide for mTHP collapse Nico Pache
11 siblings, 0 replies; 17+ messages in thread
From: Nico Pache @ 2025-04-14 22:05 UTC (permalink / raw)
To: linux-mm, linux-doc, linux-kernel, linux-trace-kernel
Cc: akpm, corbet, rostedt, mhiramat, mathieu.desnoyers, david, baohua,
baolin.wang, ryan.roberts, willy, peterx, ziy, wangkefeng.wang,
usamaarif642, sunnanyong, vishal.moola, thomas.hellstrom, yang,
kirill.shutemov, aarcange, raquini, dev.jain, anshuman.khandual,
catalin.marinas, tiwai, will, dave.hansen, jack, cl, jglisse,
surenb, zokeefe, hannes, rientjes, mhocko
Add the order to the tracepoints to give better insight into what order
is being operated at for khugepaged.
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 9d5c00b0285c..ea2fe20a39f5 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 page *page, int none_or_zero,
- int referenced, bool writable, int status),
+ int referenced, bool writable, int status, int order),
- TP_ARGS(page, none_or_zero, referenced, writable, status),
+ TP_ARGS(page, 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 86e4c5100181..8cbde2ae0112 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->page, 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->page, none_or_zero,
- referenced, writable, result);
+ referenced, writable, result, order);
return result;
}
@@ -1097,7 +1098,8 @@ 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;
}
@@ -1318,7 +1320,7 @@ 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;
}
--
2.48.1
^ permalink raw reply related [flat|nested] 17+ messages in thread* [PATCH v3 11/12] khugepaged: add per-order mTHP khugepaged stats
2025-04-14 22:05 [PATCH v3 00/12] khugepaged: mTHP support Nico Pache
` (9 preceding siblings ...)
2025-04-14 22:05 ` [PATCH v3 10/12] khugepaged: improve tracepoints for mTHP orders Nico Pache
@ 2025-04-14 22:05 ` Nico Pache
2025-04-14 22:05 ` [PATCH v3 12/12] Documentation: mm: update the admin guide for mTHP collapse Nico Pache
11 siblings, 0 replies; 17+ messages in thread
From: Nico Pache @ 2025-04-14 22:05 UTC (permalink / raw)
To: linux-mm, linux-doc, linux-kernel, linux-trace-kernel
Cc: akpm, corbet, rostedt, mhiramat, mathieu.desnoyers, david, baohua,
baolin.wang, ryan.roberts, willy, peterx, ziy, wangkefeng.wang,
usamaarif642, sunnanyong, vishal.moola, thomas.hellstrom, yang,
kirill.shutemov, aarcange, raquini, dev.jain, anshuman.khandual,
catalin.marinas, tiwai, will, dave.hansen, jack, cl, jglisse,
surenb, zokeefe, hannes, rientjes, mhocko
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 | 16 +++++++++++++---
3 files changed, 23 insertions(+), 3 deletions(-)
diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
index 2acd9c1fc558..95be9d266eff 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 6db73d2d0962..35515bff392b 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 8cbde2ae0112..d35abae76c93 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;
@@ -1060,6 +1069,7 @@ static int __collapse_huge_page_swapin(struct mm_struct *mm,
/* Dont swapin for mTHP collapse */
if (order != HPAGE_PMD_ORDER) {
+ count_mthp_stat(order, MTHP_STAT_COLLAPSE_EXCEED_SHARED);
result = SCAN_EXCEED_SWAP_PTE;
goto out;
}
--
2.48.1
^ permalink raw reply related [flat|nested] 17+ messages in thread* [PATCH v3 12/12] Documentation: mm: update the admin guide for mTHP collapse
2025-04-14 22:05 [PATCH v3 00/12] khugepaged: mTHP support Nico Pache
` (10 preceding siblings ...)
2025-04-14 22:05 ` [PATCH v3 11/12] khugepaged: add per-order mTHP khugepaged stats Nico Pache
@ 2025-04-14 22:05 ` Nico Pache
2025-04-15 1:09 ` Randy Dunlap
11 siblings, 1 reply; 17+ messages in thread
From: Nico Pache @ 2025-04-14 22:05 UTC (permalink / raw)
To: linux-mm, linux-doc, linux-kernel, linux-trace-kernel
Cc: akpm, corbet, rostedt, mhiramat, mathieu.desnoyers, david, baohua,
baolin.wang, ryan.roberts, willy, peterx, ziy, wangkefeng.wang,
usamaarif642, sunnanyong, vishal.moola, thomas.hellstrom, yang,
kirill.shutemov, aarcange, raquini, dev.jain, anshuman.khandual,
catalin.marinas, tiwai, will, dave.hansen, jack, cl, jglisse,
surenb, zokeefe, hannes, rientjes, mhocko
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.
Signed-off-by: Nico Pache <npache@redhat.com>
---
Documentation/admin-guide/mm/transhuge.rst | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)
diff --git a/Documentation/admin-guide/mm/transhuge.rst b/Documentation/admin-guide/mm/transhuge.rst
index dff8d5985f0f..f0d4e78cedaa 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 +144,13 @@ 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 its 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. 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
--
2.48.1
^ permalink raw reply related [flat|nested] 17+ messages in thread* Re: [PATCH v3 12/12] Documentation: mm: update the admin guide for mTHP collapse
2025-04-14 22:05 ` [PATCH v3 12/12] Documentation: mm: update the admin guide for mTHP collapse Nico Pache
@ 2025-04-15 1:09 ` Randy Dunlap
0 siblings, 0 replies; 17+ messages in thread
From: Randy Dunlap @ 2025-04-15 1:09 UTC (permalink / raw)
To: Nico Pache, linux-mm, linux-doc, linux-kernel, linux-trace-kernel
Cc: akpm, corbet, rostedt, mhiramat, mathieu.desnoyers, david, baohua,
baolin.wang, ryan.roberts, willy, peterx, ziy, wangkefeng.wang,
usamaarif642, sunnanyong, vishal.moola, thomas.hellstrom, yang,
kirill.shutemov, aarcange, raquini, dev.jain, anshuman.khandual,
catalin.marinas, tiwai, will, dave.hansen, jack, cl, jglisse,
surenb, zokeefe, hannes, rientjes, mhocko
On 4/14/25 3:05 PM, Nico Pache wrote:
> 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.
>
> Signed-off-by: Nico Pache <npache@redhat.com>
> ---
> Documentation/admin-guide/mm/transhuge.rst | 9 ++++++++-
> 1 file changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/Documentation/admin-guide/mm/transhuge.rst b/Documentation/admin-guide/mm/transhuge.rst
> index dff8d5985f0f..f0d4e78cedaa 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 +144,13 @@ 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 its recommended to set max_ptes_none low.
it's
> +Ideally less than HPAGE_PMD_NR / 2 (255 on 4k page size). This will prevent
^^^ not a sentence
> +undesired "creep" behavior that leads to continuously collapsing to a larger
> +mTHP size. 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
--
~Randy
^ permalink raw reply [flat|nested] 17+ messages in thread