The patch titled
Subject: mm/khugepaged: bypassing unnecessary scans with MMF_DISABLE_THP check
has been added to the -mm mm-unstable branch. Its filename is
mm-khugepaged-bypassing-unnecessary-scans-with-mmf_disable_thp-check.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-khugepaged-bypassing-unnecessary-scans-with-mmf_disable_thp-check.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Lance Yang <ioworker0@xxxxxxxxx>
Subject: mm/khugepaged: bypassing unnecessary scans with MMF_DISABLE_THP check
Date: Mon, 29 Jan 2024 13:45:51 +0800
khugepaged scans the entire address space in the background for each given
mm, looking for opportunities to merge sequences of basic pages into huge
pages. However, when an mm is inserted to the mm_slots list, and the
MMF_DISABLE_THP flag is set later, this scanning process becomes
unnecessary for that mm and can be skipped to avoid redundant operations,
especially in scenarios with a large address space.
This commit introduces a check before each scanning process to test the
MMF_DISABLE_THP flag for the given mm; if the flag is set, the scanning
process is bypassed, thereby improving the efficiency of khugepaged.
Link: https://lkml.kernel.org/r/20240129054551.57728-1-ioworker0@xxxxxxxxx
Signed-off-by: Lance Yang <ioworker0@xxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Minchan Kim <minchan@xxxxxxxxxx>
Cc: Muchun Song <songmuchun@xxxxxxxxxxxxx>
Cc: Peter Xu <peterx@xxxxxxxxxx>
Cc: Zach O'Keefe <zokeefe@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/khugepaged.c | 18 ++++++++++++------
1 file changed, 12 insertions(+), 6 deletions(-)
--- a/mm/khugepaged.c~mm-khugepaged-bypassing-unnecessary-scans-with-mmf_disable_thp-check
+++ a/mm/khugepaged.c
@@ -410,6 +410,12 @@ static inline int hpage_collapse_test_ex
return atomic_read(&mm->mm_users) == 0;
}
+static inline int hpage_collapse_test_exit_or_disable(struct mm_struct *mm)
+{
+ return hpage_collapse_test_exit(mm) ||
+ test_bit(MMF_DISABLE_THP, &mm->flags);
+}
+
void __khugepaged_enter(struct mm_struct *mm)
{
struct khugepaged_mm_slot *mm_slot;
@@ -1422,7 +1428,7 @@ static void collect_mm_slot(struct khuge
lockdep_assert_held(&khugepaged_mm_lock);
- if (hpage_collapse_test_exit(mm)) {
+ if (hpage_collapse_test_exit_or_disable(mm)) {
/* free mm_slot */
hash_del(&slot->hash);
list_del(&slot->mm_node);
@@ -2360,7 +2366,7 @@ static unsigned int khugepaged_scan_mm_s
goto breakouterloop_mmap_lock;
progress++;
- if (unlikely(hpage_collapse_test_exit(mm)))
+ if (unlikely(hpage_collapse_test_exit_or_disable(mm)))
goto breakouterloop;
vma_iter_init(&vmi, mm, khugepaged_scan.address);
@@ -2368,7 +2374,7 @@ static unsigned int khugepaged_scan_mm_s
unsigned long hstart, hend;
cond_resched();
- if (unlikely(hpage_collapse_test_exit(mm))) {
+ if (unlikely(hpage_collapse_test_exit_or_disable(mm))) {
progress++;
break;
}
@@ -2390,7 +2396,7 @@ skip:
bool mmap_locked = true;
cond_resched();
- if (unlikely(hpage_collapse_test_exit(mm)))
+ if (unlikely(hpage_collapse_test_exit_or_disable(mm)))
goto breakouterloop;
VM_BUG_ON(khugepaged_scan.address < hstart ||
@@ -2408,7 +2414,7 @@ skip:
fput(file);
if (*result == SCAN_PTE_MAPPED_HUGEPAGE) {
mmap_read_lock(mm);
- if (hpage_collapse_test_exit(mm))
+ if (hpage_collapse_test_exit_or_disable(mm))
goto breakouterloop;
*result = collapse_pte_mapped_thp(mm,
khugepaged_scan.address, false);
@@ -2450,7 +2456,7 @@ breakouterloop_mmap_lock:
* 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 (hpage_collapse_test_exit_or_disable(mm) || !vma) {
/*
* Make sure that if mm_users is reaching zero while
* khugepaged runs here, khugepaged_exit will find
_
Patches currently in -mm which might be from ioworker0@xxxxxxxxx are
mm-khugepaged-bypassing-unnecessary-scans-with-mmf_disable_thp-check.patch
