The quilt patch titled
Subject: mm/khugepaged: add flag to predicate khugepaged-only behavior
has been removed from the -mm tree. Its filename was
mm-khugepaged-add-flag-to-predicate-khugepaged-only-behavior.patch
This patch was dropped because it was merged into the mm-stable branch
of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
------------------------------------------------------
From: "Zach O'Keefe" <zokeefe@xxxxxxxxxx>
Subject: mm/khugepaged: add flag to predicate khugepaged-only behavior
Date: Wed, 6 Jul 2022 16:59:24 -0700
Add .is_khugepaged flag to struct collapse_control so khugepaged-specific
behavior can be elided by MADV_COLLAPSE context.
Start by protecting khugepaged-specific heuristics by this flag. In
MADV_COLLAPSE, the user presumably has reason to believe the collapse will
be beneficial and khugepaged heuristics shouldn't prevent the user from
doing so:
1) sysfs-controlled knobs khugepaged_max_ptes_[none|swap|shared]
2) requirement that some pages in region being collapsed be young or
referenced
[zokeefe@xxxxxxxxxx: consistently order cc->is_khugepaged and pte_* checks]
Link: https://lkml.kernel.org/r/20220720140603.1958773-3-zokeefe@xxxxxxxxxx
Link: https://lore.kernel.org/linux-mm/Ys2qJm6FaOQcxkha@xxxxxxxxxx/
Link: https://lkml.kernel.org/r/20220706235936.2197195-7-zokeefe@xxxxxxxxxx
Signed-off-by: Zach O'Keefe <zokeefe@xxxxxxxxxx>
Reviewed-by: Yang Shi <shy828301@xxxxxxxxx>
Cc: Alex Shi <alex.shi@xxxxxxxxxxxxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: Arnd Bergmann <arnd@xxxxxxxx>
Cc: Axel Rasmussen <axelrasmussen@xxxxxxxxxx>
Cc: Chris Kennelly <ckennelly@xxxxxxxxxx>
Cc: Chris Zankel <chris@xxxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Cc: Helge Deller <deller@xxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Ivan Kokshaysky <ink@xxxxxxxxxxxxxxxxxxxx>
Cc: James Bottomley <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx>
Cc: Jens Axboe <axboe@xxxxxxxxx>
Cc: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Matt Turner <mattst88@xxxxxxxxx>
Cc: Max Filippov <jcmvbkbc@xxxxxxxxx>
Cc: Miaohe Lin <linmiaohe@xxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Minchan Kim <minchan@xxxxxxxxxx>
Cc: Pasha Tatashin <pasha.tatashin@xxxxxxxxxx>
Cc: Pavel Begunkov <asml.silence@xxxxxxxxx>
Cc: Peter Xu <peterx@xxxxxxxxxx>
Cc: Rongwei Wang <rongwei.wang@xxxxxxxxxxxxxxxxx>
Cc: SeongJae Park <sj@xxxxxxxxxx>
Cc: Song Liu <songliubraving@xxxxxx>
Cc: Thomas Bogendoerfer <tsbogend@xxxxxxxxxxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Zi Yan <ziy@xxxxxxxxxx>
Cc: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
Cc: "Souptick Joarder (HPE)" <jrdr.linux@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/khugepaged.c | 83 ++++++++++++++++++++++++++++++++--------------
1 file changed, 58 insertions(+), 25 deletions(-)
--- a/mm/khugepaged.c~mm-khugepaged-add-flag-to-predicate-khugepaged-only-behavior
+++ a/mm/khugepaged.c
@@ -73,6 +73,8 @@ static DECLARE_WAIT_QUEUE_HEAD(khugepage
* default collapse hugepages if there is at least one pte mapped like
* it would have happened if the vma was large enough during page
* fault.
+ *
+ * Note that these are only respected if collapse was initiated by khugepaged.
*/
static unsigned int khugepaged_max_ptes_none __read_mostly;
static unsigned int khugepaged_max_ptes_swap __read_mostly;
@@ -86,6 +88,8 @@ static struct kmem_cache *mm_slot_cache
#define MAX_PTE_MAPPED_THP 8
struct collapse_control {
+ bool is_khugepaged;
+
/* Num pages scanned per node */
u32 node_load[MAX_NUMNODES];
@@ -554,6 +558,7 @@ static bool is_refcount_suitable(struct
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 page *page = NULL;
@@ -566,8 +571,10 @@ static int __collapse_huge_page_isolate(
pte_t pteval = *_pte;
if (pte_none(pteval) || (pte_present(pteval) &&
is_zero_pfn(pte_pfn(pteval)))) {
+ ++none_or_zero;
if (!userfaultfd_armed(vma) &&
- ++none_or_zero <= khugepaged_max_ptes_none) {
+ (!cc->is_khugepaged ||
+ none_or_zero <= khugepaged_max_ptes_none)) {
continue;
} else {
result = SCAN_EXCEED_NONE_PTE;
@@ -587,11 +594,14 @@ static int __collapse_huge_page_isolate(
VM_BUG_ON_PAGE(!PageAnon(page), page);
- if (page_mapcount(page) > 1 &&
- ++shared > khugepaged_max_ptes_shared) {
- result = SCAN_EXCEED_SHARED_PTE;
- count_vm_event(THP_SCAN_EXCEED_SHARED_PTE);
- goto out;
+ if (page_mapcount(page) > 1) {
+ ++shared;
+ if (cc->is_khugepaged &&
+ shared > khugepaged_max_ptes_shared) {
+ result = SCAN_EXCEED_SHARED_PTE;
+ count_vm_event(THP_SCAN_EXCEED_SHARED_PTE);
+ goto out;
+ }
}
if (PageCompound(page)) {
@@ -654,10 +664,14 @@ static int __collapse_huge_page_isolate(
if (PageCompound(page))
list_add_tail(&page->lru, compound_pagelist);
next:
- /* There should be enough young pte to collapse the page */
- if (pte_young(pteval) ||
- page_is_young(page) || PageReferenced(page) ||
- mmu_notifier_test_young(vma->vm_mm, address))
+ /*
+ * If collapse was initiated by khugepaged, check that there is
+ * enough young pte to justify collapsing the page
+ */
+ if (cc->is_khugepaged &&
+ (pte_young(pteval) || page_is_young(page) ||
+ PageReferenced(page) || mmu_notifier_test_young(vma->vm_mm,
+ address)))
referenced++;
if (pte_write(pteval))
@@ -666,7 +680,7 @@ next:
if (unlikely(!writable)) {
result = SCAN_PAGE_RO;
- } else if (unlikely(!referenced)) {
+ } else if (unlikely(cc->is_khugepaged && !referenced)) {
result = SCAN_LACK_REFERENCED_PAGE;
} else {
result = SCAN_SUCCEED;
@@ -745,6 +759,7 @@ static void khugepaged_alloc_sleep(void)
struct collapse_control khugepaged_collapse_control = {
+ .is_khugepaged = true,
.last_target_node = NUMA_NO_NODE,
};
@@ -1025,7 +1040,7 @@ static int collapse_huge_page(struct mm_
mmu_notifier_invalidate_range_end(&range);
spin_lock(pte_ptl);
- result = __collapse_huge_page_isolate(vma, address, pte,
+ result = __collapse_huge_page_isolate(vma, address, pte, cc,
&compound_pagelist);
spin_unlock(pte_ptl);
@@ -1116,7 +1131,9 @@ static int khugepaged_scan_pmd(struct mm
_pte++, _address += PAGE_SIZE) {
pte_t pteval = *_pte;
if (is_swap_pte(pteval)) {
- if (++unmapped <= khugepaged_max_ptes_swap) {
+ ++unmapped;
+ if (!cc->is_khugepaged ||
+ unmapped <= khugepaged_max_ptes_swap) {
/*
* Always be strict with uffd-wp
* enabled swap entries. Please see
@@ -1134,8 +1151,10 @@ static int khugepaged_scan_pmd(struct mm
}
}
if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) {
+ ++none_or_zero;
if (!userfaultfd_armed(vma) &&
- ++none_or_zero <= khugepaged_max_ptes_none) {
+ (!cc->is_khugepaged ||
+ none_or_zero <= khugepaged_max_ptes_none)) {
continue;
} else {
result = SCAN_EXCEED_NONE_PTE;
@@ -1165,11 +1184,14 @@ static int khugepaged_scan_pmd(struct mm
goto out_unmap;
}
- if (page_mapcount(page) > 1 &&
- ++shared > khugepaged_max_ptes_shared) {
- result = SCAN_EXCEED_SHARED_PTE;
- count_vm_event(THP_SCAN_EXCEED_SHARED_PTE);
- goto out_unmap;
+ if (page_mapcount(page) > 1) {
+ ++shared;
+ if (cc->is_khugepaged &&
+ shared > khugepaged_max_ptes_shared) {
+ result = SCAN_EXCEED_SHARED_PTE;
+ count_vm_event(THP_SCAN_EXCEED_SHARED_PTE);
+ goto out_unmap;
+ }
}
page = compound_head(page);
@@ -1220,14 +1242,22 @@ static int khugepaged_scan_pmd(struct mm
result = SCAN_PAGE_COUNT;
goto out_unmap;
}
- if (pte_young(pteval) ||
- page_is_young(page) || PageReferenced(page) ||
- mmu_notifier_test_young(vma->vm_mm, address))
+
+ /*
+ * If collapse was initiated by khugepaged, check that there is
+ * enough young pte to justify collapsing the page
+ */
+ if (cc->is_khugepaged &&
+ (pte_young(pteval) || page_is_young(page) ||
+ PageReferenced(page) || mmu_notifier_test_young(vma->vm_mm,
+ address)))
referenced++;
}
if (!writable) {
result = SCAN_PAGE_RO;
- } else if (!referenced || (unmapped && referenced < HPAGE_PMD_NR/2)) {
+ } else if (cc->is_khugepaged &&
+ (!referenced ||
+ (unmapped && referenced < HPAGE_PMD_NR / 2))) {
result = SCAN_LACK_REFERENCED_PAGE;
} else {
result = SCAN_SUCCEED;
@@ -1896,7 +1926,9 @@ static int khugepaged_scan_file(struct m
continue;
if (xa_is_value(page)) {
- if (++swap > khugepaged_max_ptes_swap) {
+ ++swap;
+ if (cc->is_khugepaged &&
+ swap > khugepaged_max_ptes_swap) {
result = SCAN_EXCEED_SWAP_PTE;
count_vm_event(THP_SCAN_EXCEED_SWAP_PTE);
break;
@@ -1947,7 +1979,8 @@ static int khugepaged_scan_file(struct m
rcu_read_unlock();
if (result == SCAN_SUCCEED) {
- if (present < HPAGE_PMD_NR - khugepaged_max_ptes_none) {
+ if (cc->is_khugepaged &&
+ present < HPAGE_PMD_NR - khugepaged_max_ptes_none) {
result = SCAN_EXCEED_NONE_PTE;
count_vm_event(THP_SCAN_EXCEED_NONE_PTE);
} else {
_
Patches currently in -mm which might be from zokeefe@xxxxxxxxxx are
mm-shmem-add-flag-to-enforce-shmem-thp-in-hugepage_vma_check.patch
mm-khugepaged-attempt-to-map-file-shmem-backed-pte-mapped-thps-by-pmds.patch
mm-madvise-add-file-and-shmem-support-to-madv_collapse.patch
mm-khugepaged-add-tracepoint-to-hpage_collapse_scan_file.patch
selftests-vm-dedup-thp-helpers.patch
selftests-vm-modularize-thp-collapse-memory-operations.patch
selftests-vm-add-thp-collapse-file-and-tmpfs-testing.patch
selftests-vm-add-thp-collapse-shmem-testing.patch
selftests-vm-add-file-shmem-madv_collapse-selftest-for-cleared-pmd.patch
selftests-vm-add-selftest-for-madv_collapse-of-uffd-minor-memory.patch
